Thomas Reid Inquiry And Essays Summary Definition

Thomas Reid: Philosophy of Mind

This article focuses on the philosophy of mind of Thomas Reid (1710-1796), as presented in An Inquiry into the Human Mind on the Principles of Common Sense (1764) and Essays on the Intellectual Powers of Man (1785). Reid’s action theory and his views on what makes humans morally worthy agents, although connected to philosophy of mind, are not explored here.

Reid is best known as the father of common sense philosophy. He contends that going back to the principles of common sense will help deal with the problems engendered by the so-called “skeptical views" of his predecessors: Descartes, Locke, Berkeley, and Hume. He argues that “the way of ideas” generates undue uncertainty in the theory of knowledge. If the only things that can be known directly and immediately are the contents of one’s mind, there can be no certainty in the knowledge geared toward the external world. Reid believes this goes against the common-sense view that humans do acquire certain knowledge through empirical observation of the external world, and are therefore not confined to know only the contents of their minds.

In philosophy of mind, Reid is most celebrated today for the arguments he gave in support of the position known as direct realism, which, at its most basic, states that the primary objects of sense perception are physical objects, not ideas in human minds. However, Reid’s philosophy of mind neither begins nor ends with perception. In addition to arguing for direct realism and, consequently, against “the way of ideas,” he undertook the task of establishing the equal status of the faculties of the mind, and of explaining the relationships that exist among them. He is a worthy successor of Locke, in that he believes that the mind is to be characterized in terms of a faculty psychology. He is a worthy successor of Newton, in that he believes that the scientific method is the right way of investigating the nature of mind. Reid characterized the scientific method mainly by trial and error, and by setting up experiments and drawing general conclusions from them.

One of the starting points of Reid’s philosophy of mind is a traditional distinction between the “powers of the understanding” and the “powers of the will.” Reid believes this distinction is not entirely correct because the mind is active whenever the powers of the understanding are exercised, and a certain degree of understanding is needed for any act of will. However, he uses it to classify the faculties of the mind into intellectual, on the one hand, and active, on the other.  The distinction is used in the titles of his two mature published works: Essays on the Intellectual Power of Man (1785) and Essays on the Active Powers of Man (1788), which he envisioned as two sides of the same coin. Reid thought that any theory of the mind should comprise an investigation into both types of mental operations.

Table of Contents

  1. Sensation
  2. Perception
    1. Original Perception
    2. Acquired Perception
  3. Memory
    1. General Considerations on Memory
    2. Memory and Personal Identity
  4. Intellectual Powers (Proper)
    1. Conception
      1. Bare Conception
      2. Imagination
    2. Judgment and Reasoning
      1. The Fundamental Characteristics of Judgment
      2. Common Sense
      3. First Principles of Common Sense
      4. Reasoning
  5. Taste
    1. Why This Faculty Is Called “Internal Taste”
    2. An Objectivist Account of Beauty
  6. References and Further Reading
    1. Primary Sources
    2. Secondary Sources

1. Sensation

Reid argues that sensation is an original and simple operation of the mind, which for him means not only that certain beings (namely sentient ones) are born with an ability to sense, but also that this operation of the mind cannot be logically defined. All natural operations of the mind are simple and, in some sense, primitive, so that no reductive definition can be offered. This does not mean, however, that one cannot pay attention to the specific role played by this operation. In doing so, one will discover its most important features.

Although careful introspective observation will reveal that sensations do not usually occur on their own, but are almost always accompanied by perceptions, Reid is pointing out that a clear-cut distinction between sensation and perception exists and should be accounted for. This distinction has to do primarily with the specific roles sensations and perceptions play in the knowledge of the external world. Sensations are of limited use, in this sense; they only give information of what goes on in the sentient being. Perceptions, on the other hand, contribute to basic repository knowledge. In sensing a smell or tasting a taste, for instance, a sentient being will take notice of how its mind is affected, but, as Reid points out, such sensations bear no resemblance to any of the qualities of the external objects that cause these sensations to occur in the sentient being. Here Reid differs from his predecessors: according to John Locke, for instance, at least some sensations (those derived from the primary qualities of objects) do resemble the external objects which occasion the formation of such simple ideas in sentient beings such as humans (Locke, Essay II. viii. 15). To make the distinction with perception more vivid, Reid discusses an example: in seeing a flower or touching a sugar cube—which involves perceiving and having contentful thoughts about these objects, as is elaborated in the next section—humans gain knowledge about what these external objects really are. There still is no resemblance thesis advanced, to be sure; the mind is simply projected outside itself and, in doing so, it objectifies the things in its environment. In this, Reid is very forward-thinking: he is the first philosopher to draw a distinction between sensation and perception, which is extensively employed in contemporary philosophy of mind and psychology (as J. J. Gibson rightfully noticed).

This distinction between sensation and perception rests primarily on a peculiarity of the faculty of sensation: Reid believes that this is the only operation of the mind that “hath no object distinct from the act itself” (EIP I. 1, 36). He acknowledges the fact that human language is misleading in this respect: for instance, for both sensation and perception, people use “the same mode of expression” (IHM 6.20, 167). This mode of expression involves an active verb and an object: one can say both that “I feel a pain” and that “I see a tree” (IHM 6.20, 167). But, Reid contends, in the former case the object itself is grammatical only, and not also real, whereas in the latter the object is a real thing, allegedly existing outside the perceiver’s mind.

It is less clear what Reid means when he says that the object is not real, but grammatical only, in the case of the construction expressing a sensation that one may feel. There are two ways of interpreting this claim, and this ambiguity tracks two distinct positions in the secondary literature on Reid. On the one hand, sensations, for Reid, can be understood to not have objects at all: as such, this mental operation is distinct from all others. If we understand sensation to have no object, to be about nothing, it cannot ever be wrong. This would mark sensation as a very special faculty among the faculties of the human mind; perception or memory are not like this: someone can misperceive a tree just as well as he can misremember having seen a tree. But a person can never be mistaken about a feeling that particular person has: whenever someone has a headache, that ache is real and it is that person’s and it is exactly as that person is feeling it. On the other hand, that passage has been read as saying that sensations take themselves as objects; Reid, in this interpretation, would subscribe to a reflexive view of sensations. Just like perceptions and memories, sensations are constituted by two other ingredients: a conception of the object, and a belief that the object exists, except, in the case of sensation, this object is the sensation itself, not an external object like trees, frogs, or human beings.

A consequence of understanding Reid as saying that sensations do not have any kind of objects is to think that he is a precursor of “adverbial” theories of sensation. In this account, a sentient being is not said to have a sensation of a red object, but to sense in a certain way whenever stimulated in the right manner. Sensations inform the sentient being of various ways of feeling: there is a particular way of feeling redly, as opposed to a particular way of feeling yellowly, and there is yet another way of feeling headachely (see also Sense-Data). Understanding that sensations provide us with a qualitative feel and making sense of what exactly this means has become very important in early 21st century discussions on the nature of mind and consciousness. According to some authors, such as David Chalmers, Frank Jackson, Joseph Levine, and Thomas Nagel, qualia offer sufficient proof that a complete reduction of all mental processes to purely physical processes (as described by a physicalist interpretation of brain processes) is impossible (for more, see Qualia). So, understanding Reid’s position in this manner will place him squarely in the same tradition as one of the most important debates in contemporary philosophy of mind.

The last attribute of sensations worth mentioning is their role as signs of external objects. Usually, sensations pass unnoticed (unless the sentient being carefully attends to them) to other things that they signify. This feature of sensations allows Reid to argue that they are never to be associated to Lockean ideas (Locke, Essay II. viii. 8): they are not the objects of perception, and, moreover, they are not mental intermediaries between the mind and the world. Perception of external objects turns out to be immediate, in Reid’s view (Reid on sensations as signs: IHM 2. 10, 43; IHM 4. 1, 49; IHM 6. 21, 177). To properly understand the role of sensations as signs of external objects, according to Reid, an analysis of perception should be given, a task undertaken in the next section.

2. Perception

Perception is the main faculty that has the role to give beings endowed with this faculty brute knowledge about the external world: the knowledge is brute because no reasoning enters perception; and the result is knowledge, even though sometimes when the perceiver believes that something is being perceived, something is actually being either perceptually illusioned or hallucinated. However, even when a perceptual state results in a false outcome, the state itself should be characterized as perception (for more on how and why perception can be non-veridical, see EIP II. 22, 241–252). So, this is how sensations, as signs of external things, work to connect minds with external things. Reid argues that:

[A] requisite to our knowing things by signs is, that the appearance of the sign to the mind, be followed by the conception and belief of the thing signified. Without this the sign is not understood or interpreted; and therefore is no sign to us. […] Now, there are three ways in which the mind passes from the appearance of a natural sign to the conception and belief of the thing signified; by original principles of our constitution, by custom, and by reasoning. (IHM 6. 21, 177)

This passage is important in several respects: (i) it gives Reid’s “official” characterization of perception, and (ii) it lays the foundation for an important distinction at the level of perception. These two aspects are discussed in turn.

First, Reid argues that “the appearance of the sign” is followed by a conception and belief of the thing signified. When Reid gives his official characterization of perception he states that this faculty involves several others: the occurrence of a sensation suggests a conception and a belief of the existence of the thing perceived. Moreover, this existential belief is immediate, and not the product of reasoning (EIP II. 6, 96). If it were the product of reasoning, “the greatest part of men would be destitute of [the information had of external objects]; for the greater part of men hardly ever learn to reason; and in infancy and childhood no man can reason” (EIP II. 6, 101). Perception, therefore, must be able to occur independently from any act of reasoning.

The second feature of perception that the passage quoted above refers to is the distinction Reid draws between original perception and acquired perception: in the case of original perception, a natural sign (that is, a sensation) suggests a conception and a belief “by original principles of our constitution.” In the case of acquired perception, by contrast, the natural sign in question suggests a conception and a belief “by custom,” which most probably means “habit” and/or “experience.” Let us take a closer look at this distinction by pinning down some of the essential features of original perception, and by emphasizing some of the points of departures from this model, in the case of acquired perception.

a. Original Perception

According to Reid (IHM 6. 20, 171 and EIP II. 21), only two of the senses give beings endowed with them original perceptions, namely those of touch and sight. The sense of sight is somewhat problematic in this respect, though, since vision does not provide creatures endowed with it with original visual perceptions of some things, for instance depth, but only with acquired ones. In original tactile perception, the sensation had of the so-called “primary qualities of bodies” immediately suggests a conception and belief of the existence of these qualities, and of substances in which such qualities inhere. In original visual perception, the sensations of colors suggest conceptions and beliefs of the existence of the so-called “secondary quality” of color as existing outside of minds, in an external object. The perception of visible figure is also supposed to be original, according to Reid and, according to the standard interpretation of Reid, it is not accompanied by any type of visual sensation whatsoever. Why does Reid think that only two of the senses—touch and vision—can give beings that have them original perceptions?  Why cannot smell, taste, and hearing provide such beings with original perceptions? Can this have anything to do with the distinction between primary and secondary qualities of objects?  This is a good place to offer some details on Reid’s view of the distinction between primary and secondary qualities of objects. As previously mentioned, Reid thinks that Locke was wrong to believe that there is some resemblance between primary qualities of objects and the ideas or sensations sentient beings have of them. However, Reid himself draws a distinction between these two types of properties of objects:

There appears to be a real foundation for the distinction, and it is this: That our senses give us a direct and distinct notion of the primary qualities, and inform us what they are in themselves: But of the secondary qualities, our senses give us only a relative and obscure notion. They inform us only, that they are qualities that affect us in a certain manner, that is, produce in us a certain sensation; but as to what they are in themselves, our senses leave us in the dark. ([emphasis added]; EIP II. 17, 201)

Reid argues that knowledge of primary qualities—like squareness, or hardness, or motion—is direct: it captures everything there is to know about such a quality. Squareness, hardness, motion, and all the other mathematical qualities of bodies are known intrinsically. The conception human beings have of secondary qualities, like color, for instance, is not like this; hence it does not constitute knowledge. All there is to know about a secondary quality is that sentient beings are constituted in such a way that whenever a normal being is in contact with the color red, under normal conditions, that being gets a sensation, which is different in what it feels like to that being from the sensation that same being gets whenever it is stimulated with the color yellow, under normal conditions. Other examples of primary qualities of bodies include shape, size, and solidity. Besides color, other examples of secondary qualities are heat, cold, smell, and taste..

This distinction is important for understanding Reid’s view of original perception, since one way of drawing this distinction is by reference to what kinds of things can be originally perceived, as opposed to what kinds of things can be perceived only in an acquired manner. It might seem that the distinction between original and acquired perception is essentially linked with the more traditional one between primary and secondary qualities of bodies. This is indeed what several scholars have argued, citing as main evidence for this interpretation the fact that human beings have direct conceptions only of primary qualities. Based on this type of conception, human beings gain knowledge only of primary qualities and, if perception is supposed to give perceivers knowledge, as Reid thinks, it seems clear that perceivers can perceive only primary qualities of bodies, since perceivers do not gain any knowledge, by their senses, of secondary qualities. This argument seems correct, but it has a severe uphill battle because Reid specifically and consistently places color, a secondary quality, on the list of things that can be originally perceived (IHM 6. 20 p. 171; EIP II. 21, p. 236). So, if we are to listen to Reid, the distinction between primary and secondary qualities, on the one hand, and the distinction between original and acquired perception, on the other, do not carve the world in the same way. The distinction between original and acquired perception, therefore, must be clarified in a different way.

b. Acquired Perception

Acquired perception is distinguished from original perception primarily by the role of learning and experience. There is no need for any type of experience, according to Reid, for human beings to be able to perceive the primary qualities of bodies and the bodies themselves by touching them, for instance. However, one must learn to associate a certain sign that conjures up an original perception or a sensation only, with a certain external object. There is a controversy in the literature concerning what exactly this learning involves: according to some authors (for example, Van Cleve (2004)), it initially involves inference or reasoning, thus excluding anything that we acquire in this way from the list of things that we actually perceive, since perception, for Reid is a faculty that does not rest on the perceiver’s reasoning powers, as indicated in the previous section (EIP II. 6, 101). According to other authors (such as Copenhaver (2010)), however, acquired perception never involves any type of reasoning. Rather, Reid intended acquired perception to be understood as a distinctively perceptual ability: with the passage of time, normal perceivers acquire more perceptual sensitivity to properties not represented in original perception. Here is Reid explaining how this happens in the case of perception of depth and three-dimensional figure by sight:

It is experience that teaches me that the variation of colour is an effect of spherical convexity […]. But so rapid is the progress of the thought, from the effect to the cause, that we attend only to the last, and can hardly be persuaded that we do not immediately see the three dimensions of the sphere. (EIP II.21, 236)

The fact that this type of ability is called “acquired” should not suggest that it is less natural than the original variety. Beings endowed with the ability to develop acquired perception do not develop this ability consciously or only because they decide to acquire certain perceptions. Here is what Reid says concerning this:

In acquired perception, the signs are either sensations, or things which we perceive by means of sensations. The connection between the sign and the thing signified, is established by nature: and we discover this connection by experience; but not without the aid of our original perceptions, or of those which we have already acquired. After this connection is discovered, the sign, in like manner as in original perception, always suggests the thing signified, and creates the belief of it. (IHM 6. 24, 191)

Acquired perception thus builds upon the original abilities of sensing and originally perceiving things in nature that human beings have. In acquired perception, in contrast to original perception, the conventional associations between signs and things signified are introduced by a combination between nature and experience. In original perception, these conventions are the result of nature alone: this is the way humans are constituted. Reid believes that acquired perceptions are far more numerous than original perceptions (EIP XXI. 21, 235).

3. Memory

a. General Considerations on Memory

Memory, for Reid, is the perfect counterpart to perception: it is an original faculty of minds, which is meant to give beings endowed with it immediate access to the past. He argues that it is a first principle of common sense “[t]hat those things did really happen which I distinctly remember” ([emphasis added]; EIP VI. 5, p. 474) and that the knowledge that memory gives is “immediate knowledge of things past” (EIP II. 1, p. 253). No mental entities, such as ideas, mediate a being’s access to the external world in memory, just like no such entities mediate such a being’s access to the world in perception. There are three things involved in perception, and, similarly, there are three things involved in memory: a mind, a faculty, and an external object, which the mind gains knowledge of via the faculty in question. For Reid, “[m]emory implies a conception and belief of past duration” (EIP III. 1, p. 254). This formulation mirrors the one that he gave to further explain how perception operates, although both in the case of memory and of perception, these explanations are not definitions, since both these faculties are simple, and hence cannot be reductively defined by analyzing their components. The external object, in the case of perception, is (allegedly) presently existing; the external object, in the case of memory, was (allegedly) existing in the past of the mind having the memory in question. Beings endowed with perception can be said to mis-perceive things—which are either different than they appear to be or do not exist altogether; and beings endowed with memory can be said to mis-remember things—which were either different than they appeared to such beings or did not exist altogether. To present his own views on memory, Reid starts by first criticizing his precursors, primarily Locke and Hume, for operating with a so-called “store-house” model of memory. Contrary to what he takes Locke and Hume to be saying, memory is not a repository for ideas, which can be revived, whenever the person who had those ideas needs them again (for example, Locke, Essay II.xx.2). The main problem here, according to Reid, is that if an idea could indeed be revived in this way, that idea would be perceived again, and not actually remembered. This is because, as Reid understands them, Locke and Hume argue that ideas are the immediate objects of perception. So, whenever an idea is present to the mind—whether for the first time or when it is revived—the mind should be said to perceive it. What does memory contribute here, Reid asks?  Even though Reid is not the most charitable interpreter of Locke or of Hume, some of the criticisms he raises are cogent. There is a threat of circularity in the account of memory offered by both Locke and Hume, as Reid understands them. Both Locke and Hume’s accounts of memory seem to presuppose memory, rather than explain it: the ability to understand that a certain idea that is now present to the mind is exactly the same, qualitatively, and not numerically (since both Locke and Hume believe that ideas are fleeting), as an idea that was present to the mind at a previous moment of time, needs memory. The problem is that no idea contains any information, qualitative or representational, that could be used to identify that idea as being about the past.

So, what is Reid’s positive account of memory?  Here is what he says at the beginning of the Essay on memory:

Things remembered must be things formerly perceived or known. I remember the transit of Venus over the sun in the year 1769. I must therefore have perceived it at the time it happened, otherwise I could not now remember it. Our first acquaintance with any object of thought cannot be by remembrance. Memory can only produce continuance or renewal of a former acquaintance with the thing remembered. (EIP III. 1, p. 253-55)

This suggests that Reid is operating with a precursor of a distinction used in the psychological literature of the twentieth century, as advanced primarily by Tulving (1983). According to Tulving (1983) there are two main types of long-term memory: procedural—whereby one remembers how to perform certain actions (for instance, one remembers how to ride a bike or how to bake a cake), and declarative. This latter type is itself divided into episodic memory—whereby one remembers an experience that one underwent or an event one witnessed (for example, somebody remembers running in her first 5K race); and semantic memory—whereby one remembers that so-and-so is the case, where the fact remembered may be something that happened before one’s time (such as when one remembers that Napoleon was defeated at Waterloo). Semantic memory is further distinguished from the episodic kind by the so-called “previous awareness condition” on episodic memory, which requires for someone to have been there in a capacity of witness or agent of an event, for that event to be episodically remembered. Reid thinks that something like the previous awareness condition on episodic memory must be satisfied in cases like the one quoted above: for someone to remember something, that person must have perceived that thing at an earlier moment of time.

There is a debate among Reid scholars concerning this very issue: did Reid think that all memory should be understood as episodic, or did he have room in his theory for semantic memory as well?  Some authors believe that, for Reid, all memory is episodic (for instance, Van Woudenberg (1999)); others believe that Reid was concerned with both semantic and episodic memory (such as Copenhaver (2009)). The consensus in the literature is, however, that Reid had nothing very interesting to say about procedural memory. This is important since it shows Reid to be very forward-thinking in his treatment of memory: he believes that episodic memory is fundamental for a being’s immediate knowledge of its past.

So, how does memory connect a being endowed with such a faculty with past events?  According to Reid, memory does not offer a being endowed with this faculty a present connection with an event experienced in the past. The access to past events is not by re-acquaintance, as Locke or Hume would say. The past acquaintance of the event itself is preserved through the conception and belief deployed in a memorial experience. This is because, according to Reid, apprehension, when employed by another faculty, such as perception and consciousness, is strictly related to the present moment:

It is by memory that we have an immediate knowledge of things past: The senses give us information of things only as they exist in the present moment; and this information, if it were not preserved by memory, would vanish instantly, and leave us as ignorant as if it had never been. (EIP III. 1, p. 253)

b. Memory and Personal Identity

Reid is famous for his criticism of Locke’s theory of personal identity. The success of this criticism depends on the explanation of the relationship that perception and consciousness, on the one hand, and memory, on the other, have with time. Perception and consciousness give a being endowed with such faculties immediate knowledge of presently existing things: of how the external world is, and of how the mental operations of the minds of such beings succeed one another, respectively. Memory, on the other hand, gives beings endowed with this faculty immediate knowledge of things past; and these things can be, in turn, external or internal. Someone can remember, for instance, having a certain nauseating sensation upon encountering some rotten food. That person will not only remember the state of the food, in this case, but also his having a certain unpleasant sensation.

Reid finds Locke’s theory of personal identity lacking on two counts: (i) first, Locke suggests that consciousness can extend to the past (Essay II.xxvii.9); (ii) second, Reid thinks that Locke is claiming that personal identity consists in memory—sometimes this theory of personal identity is called “the memory theory of personal identity.” The two issues are related, and the first one might very well be terminological: what Locke meant by “consciousness,” in this context, Reid means by “memory”:

Mr Locke attributes to consciousness the conviction we have of our past actions, as if a man may now be conscious of what he did twenty years ago. It is impossible to understand the meaning of this, unless by consciousness is meant memory, the only faculty by which we have an immediate knowledge of our past actions. (EIP III. 6, p. 277)

The second issue is more serious. The problem has to do with the fact that Locke seems to require sameness of memory for sameness of person. The type of memory involved here is episodic memory, and this might be why Locke thinks that consciousness is something that is needed here: in order to remember something about oneself episodically, a person must remember the event “from the inside.” For instance, if someone remembers, episodically, having run a 5K race this past Sunday, that person cannot be mistaken regarding who was the agent of the act of running in the race. That particular person also could not be mistaken about what it felt like to run a 5K this past Sunday. These are all characteristics of episodic memory. Furthermore, if that particular person cannot be mistaken with regard to who was the agent of this act of running (namely that person himself), then that particular person must have existed this past Sunday, at the time of the race. In thinking that memory is necessary for personal identity, Locke doesn’t seem to commit a grave error of reasoning.

Reid, however, argues that this account is absurd, because it leads to absurd consequences. To show that he is right, Reid discusses the now famous case of the brave officer:

Suppose a brave officer to have been flogged when a boy at school, for robbing an orchard, to have taken a standard from the enemy in his first campaign, and to have been made a general in advanced life: Suppose also, which must be admitted to be possible, that when made a general he was conscious of his taking the standard, but had absolutely lost the consciousness of his flogging.

These things being supposed, it follows, from Mr. LOCKE’s doctrine, that he who was flogged at school is the same person who took the standard, and that he who took the standard is the same person who was made a general. When it follows, if there be any truth in logic, that the general is the same person with him who was flogged at school. But the general’s consciousness does not reach so far back as his flogging, therefore, according to Mr. LOCKE’s doctrine, he is not the person who was flogged. Therefore the general is, and at the same time is not the same person as him who was flogged at school. (EIP III. 6, p. 276)

This case, which builds upon an objection raised by Joseph Butler (1736), is supposed to show that personal identity, understood as consisting in memory, is not a consistent notion. Here is why: due to the transitivity of numerical identity, the old general should be numerically identical with the kid who was flogged for robbing an orchard. This should follow, on the assumption that the kid who was flogged is numerically the same as the brave officer, who, in turn, is supposed to be numerically the same as the old general. Memory ensures that the boy who was flogged is the same as the brave officer, since the brave officer remembers that incident from his childhood. It ensures, moreover, that the general is the same as the brave officer, since the general remembers (episodically) that event from his youth. But, on Locke’s theory of identity, Reid claims, the general is not the same person as the kid robbing the orchard, since the general does not remember (episodically) that event from his childhood. There are two possibilities: (i) either to explain personal identity without making recourse to numerical identity, since transitivity holds for numerical identity, but this example shows that transitivity fails for personal identity. Or, (ii) to give up Locke’s theory of personal identity, since any theory that does not respect the rules of logic is irremediably flawed.

Reid chooses (ii) and argues that memory is neither necessary nor sufficient for personal identity. Memory is not a necessary condition for personhood, since during their lives, human beings witness or are the agents of many events of which they have no recollection at later moments of time. However, it would be absurd to claim that just because someone doesn’t remember something having happened, that person wasn’t actually there. Here is what Reid says on the issue: “I may have other good evidence of things which befell me, and which I do not remember: I know who bare me, and suckled me, but I do not remember these events” (EIP III. 4, p. 264). Neither is memory a sufficient condition for personal identity, according to Reid, since even though someone may be able to remember episodically that he was the agent or the witness of an event, it is not his remembering the event that makes it the case that he himself is the same person he was then. “It may here be observed […] that it is not my remembering any action of mine that makes me to be the person who did it. This remembrance makes me to know assuredly that I did it; but I might have done it, though I did not remember it” (EIP III. 4, p. 265). Memory gives someone immediate knowledge of a past event that person was the witness to or agent of, but it does not ensure that that person was actually there at the time of the event.

Reid’s theory of personal identity is deflationary: he argues that this notion is primitive. The only way to understand more about this relation is by contrast to other relations: “I can say that diversity is a contrary notion, and that similitude and dissimilitude are another couple of contrary relations, which every man easily distinguishes in his conception from identity and diversity” (EIP III. 4, p. 263). Just like Locke before him, Reid acknowledges that identity, in general (thus including the special case of personal identity), presupposes “an uninterrupted continuance of existence” (EIP III. 4, p. 263). Due to this feature of identity, there is no way to think that mental states and processes remain identical over time:

Hence we may infer, that identity cannot, in its proper sense, be applied to our pains, our pleasures, our thoughts, or any operation of our minds. The pain felt this day is not the same individual pain which I felt yesterday, though they may be similar in kind and degree, and have the same cause. The same may be said of every feeling, and of every operation of the mind: They are all successive in their nature like time itself, no two moments of which can be the same moment. (EIP III. 4, p. 263)

Thus, Reid thinks that persons should not be identified with their thoughts or feelings, but with the subject of such thoughts and feelings, which remains the same over time. This subject is an immaterial substance, a soul, which is best understood by reference to Leibniz’s notion of a monad (EIP III. 4, p. 264).

4. Intellectual Powers (Proper)

a. Conception

The fourth Essay is dedicated to conception, whose primary role is to be an ingredient (or concomitant) in all other operations of the mind. In this picture, conception is being used as part of the endeavor to gain knowledge of the external world (when it is employed by the senses), of the internal world (when it is employed by consciousness), and also to analyze the complex relationships that exist among the objects of the world, among numbers in mathematics, and among rules of reasoning in logic. As such, conception is a faculty that acts as a bridge, connecting the information gathered by the senses with the intellectual processing powers of judgment and reasoning.

Since conception is a simple operation of the mind, it cannot be subjected to a reductive definition any more than the other operations can be. However, as always, Reid argues that it has certain features which are useful to know in order to better understand how it functions, both when it is an ingredient or concomitant of other operations, and when it is employed on its own, as “bare conception.”

Reid argues that conception is an ingredient in all of the other operations of the human mind:

Our senses cannot give us the belief of any object, without giving some conception of it at the same time: No man can either remember or reason about things of which he hath no conception: When we will to exert any of our active powers, there must be some conception what we will to do: There can be no desire or aversion, love nor hatred, without some conception of the object: We cannot feel pain without conceiving it, though we can conceive it without feeling it. These things are self-evident. (EIP IV. 1, 296)

As already pointed out, the argument that sensations must be intentional, and hence take themselves as objects, is based on this idea that every operation of the mind has conception as an ingredient. The passage quoted above can indeed be read as saying that one must conceive of the pain one is feeling at a given moment of time in order to actually be able to feel it. However, it is controversial in Reid scholarship what exactly “conception” is supposed to mean in this context, despite its name. The issue concerns the fact that Reid believes that human beings share most of their perceptual and sensory abilities with lower-level animals and with human infants, who do not have a well-developed conceptual framework; thus, some authors argue that “conception” should not be taken to mean that unless one is able to have and deploy fully formed concepts, one will not be able to feel pain, for instance. In this interpretation, conception should be understood as the operation that allows beings endowed with this faculty to get acquainted with an object, be that object something that exists in the present, existed in the past, or will never exist.

On the other side of this controversy are those authors who point out that it is rather counter-intuitive to believe that conception does not operate via concepts—after all, the name might be indicative of something here. The role of conception, as an ingredient in all the other operations of the human mind, is to allow humans to secure a mental grip on something. Such a mental grip is secured by deploying a singular concept, understood to be something like a uniquely identifying definite description. In this interpretation, a being would not be able to have a sensation, a perception, or a memory unless it was able to deploy a singular concept, a uniquely identifying definite description isolating that thing in the world.

i. Bare Conception

Reid calls conception, as employed on its own, and not as an ingredient in any of the other operations of the human mind, “bare conception.” This suggests that when employed on its own, conception has a different role than when employed by a faculty of the mind in which it enters as an ingredient: “yet it may be found naked, detached from all others, and then it is called simple apprehension, or the bare conception of a thing” (EIP IV. 1, p. 286).

One of the most interesting features of bare conception is its ability to be used to think about objects without any heed being paid to their existence or non-existence, and also about propositions, without any judgment of their truth or falsity.

In bare conception there can neither be truth nor falsehood, because it neither affirms nor denies. Every judgment, and every proposition by which judgment is expressed, must be true or false; and the qualities of true and false, in their proper sense, can belong to nothing but to judgments, or to propositions which express judgment. In the bare conception of a thing there is no judgment, opinion, or belief included, and therefore it cannot be either true or false. (EIP IV. 1, p. 296)

Conception, in this sense, is that faculty allowing human beings to grasp the meaning of a proposition, which is the prerequisite for being able to judge a certain proposition as true or false: “it is one thing to conceive the meaning of a proposition; it is another to judge it to be true or false” (EIP I. 1, p. 25). Things are being conceived by beings endowed with this faculty in the following manner: an object is brought before the mind, with the help of conception: “I conceive an Egyptian pyramid. […] the thing conceived may be no proposition, but a simple term only, as a pyramid, an obelisk” (EIP I. 1, p. 25). Bare conception seems to require the mind of the conceiver to use certain concepts—simple terms—to bring forth objects to the mind in a way in which conception, when employed as an ingredient in other operations of the human mind, does not. This should not be surprising, though: once someone is able to think about something, even when he is not perceiving or remembering it, his mind will have established a certain grasp of that thing, classified and analyzed it, such that he will be able to think about it without using any of his other faculties. How this comes about will be better understood once Reid’s accounts of abstraction, judgment, and reasoning are presented, but it is already worth noting that it is not conception that supplies the mind with the most simple and exact notions the mind has of external things; these are acquired by using the mind’s superior reasoning powers (EIP IV. 1, p. 309).

Ideas as acts of the mind. Bare conception can be understood by analogy with painting, Reid argues, but he warns us that analogous thinking can take us only so far. Conception should be distinguished from painting, since “[t]he action of painting is one thing, the picture produced is another thing. The first is the cause, the second is the effect” (EIP IV. 1, p. 300). Reid’s worry is that that conception will be thought to work in the same way, to produce images of things in the mind, or ideas. Reid denies that this is the case, and puts forward a theory of ideas as acts of minds rather than objects of such mental operations: “Let this therefore be always remembered, that what is commonly called the image of a thing in the mind, is no more than the act or operation of the mind in conceiving it” (EIP, IV. 1, p. 300). To unpack this further, let us think about the elements involved in conceiving that the sun is yellow, for instance. Reid argues that in this act of conception, there are the following three elements: a mind, an act of conception that the sun is yellow, and the thing itself—the sun—external to the mind in question. Furthermore, he argues that there is something missing: an image in the mind, an additional representation, that has the explicit content of a yellow sun. He is willing to assert that this is just a verbal dispute, if everyone else is willing to agree with him that these images in the mind, or ideas, are nothing more than acts of conceiving—a moot point, given that everyone else was dead at the point when he was writing, and no one could have agreed with him. But, in effect, this is a serious conceptual point.

The analogy with painting should help classify conceptions into three classes, according to Reid. Just like a painter paints by using his imagination, by copying from other paintings, or by painting live subjects, there are conceptions which can be called “creatures of fancy”—like Don Quixote or Pegasus; conceptions of universals—which are analogous to paintings which copy other paintings; and conceptions of individual (existing) things—which are like paintings of live subjects.

Our conceptions, therefore, appear to be of three kinds: They are either the conceptions of individual things, the creatures of God; or they are conceptions of the meaning of general words; or they are the creatures of our own imagination. (EIP IV. 1, p. 305)

There are two issues worthy of attention in this classification: (i) Reid argues that people can name the creatures of fancy they invent, “conceive them distinctly, and reason consequentially concerning them, though they never had an existence” (EIP IV. 1, p. 301-2). And (ii) conceiving universals—like kinds and species of things—means nothing more nor less than to conceive the “meaning which other men who understand the language affix to the same words” (EIP IV. 1, p. 302). The first of these issues shows Reid to think that it is possible for fictional names to be used in the same way as regular names, even though the former category will be used to name nonexistents.

Reid’s Meinongeanism. Based on Reid’s idea that people can think and “reason consequentially” about fictional characters and objects, Nichols (2002) argued that Reid is a precursor of Meinong. Reid’s rejection of the way of ideas and his dedication to common sense philosophy are thought to amount to a rejection of the position according to which conceiving the nonexistent means nothing more than conceiving images or any other types of mental intermediaries. Centaurs, not centaur-inspired images or ideas, are the objects of such centaur thoughts. The only exception is constituted by a thought which is explicitly about a painting of a centaur, in which case it should be obvious to everyone that what is being conceived is an image, and not a mythological animal.

This one object which I conceive [a centaur], is not the image of an animal, it is an animal. I know what it is to conceive an image of an animal, and what it is to conceive an animal; and I can distinguish the one of these from the other without any danger of mistake. (EIP, IV. 2, p. 321)

Reid does not talk about different levels of existence; there is no doubt that centaurs do not exist as flesh-and-blood animals. It is important, however, to note that Reid ascribes intentionality to all the operations of the human mind, and this intentionality is to be resolved by understanding how conception works.

ii. Imagination

At the beginning of the EIP, when Reid is defining the terms he is going to use throughout the book, and at the beginning of the fourth Essay, where he lays down his views on conception, he claims that “conception” and “imagination” are synonymous words, and, moreover, that no reductive definition of these notions can be given, since they are supposed to denote simple operations of the mind. However, in the course of his analysis of conception, it becomes clear that imagination is not exactly the same thing as conception.

Reid argues that “imagination,” when used with its proper meaning, denotes a type of conception that is concerned primarily with the objects of sight (EIP IV. 3, p. 326). This restriction to sight probably has more to do with etymology than with the proper meaning of “imagination.” Imagination is supposed to apply to other senses, although Reid thinks that such uses are not altogether proper (EIP V. 6, p. 394). Any conception is of the imaginative kind when it is lively and about possible objects of sense. One consequence is that people can never be said to imagine universals, or propositions; neither are people supposed to think that anyone is imagining objects of sense, when they are actually perceiving them. A different kind of conception is responsible for the proper workings of perception.

Reid’s distinction between conception proper and imagination is one of the first instances in philosophy of mind in which imagination is presented as a faculty of the human mind related most closely to perception. Reid’s main breakthrough is his arguing that conception proper is used for understanding and acquiring general and abstract concepts, while imagination is used to think about things that might have existed, and, as such, might have presented beings endowed with such a faculty or system with perceptual stimuli.

b. Judgment and Reasoning

Reid dedicates two essays to the mental powers of judgment and reasoning with which he believes human beings to be endowed by nature. Essay VI, the one dedicated to judgment, presents the main elements of what Reid takes to be the philosophy of common sense. After a general introduction, in which he describes the fundamental characteristics of judgment, Reid argues that certain principles should be taken for granted as true. These are the first principles of common sense, which describe how the external and internal worlds work. These principles are self-evident and as such their truth cannot be demonstrated through any kind of reasoning. In the following essay, dedicated to reasoning, Reid argues that it is the purview of this faculty to produce judgments, or to combine and analyze them, in two main ways: deductively or probably. In what follows, these issues are discussed in turn, by first explaining what Reid thought about judgment, and then providing a schematic account of how deductive reasoning is supposed to be applied to the class of necessary truths, while probable reasoning is supposed to be applied to the class of contingent truths.

i. The Fundamental Characteristics of Judgment

Reid talks about judging in terms of offering mental assent or dissent to the issues represented by any particular judgment. Reid thinks that if human beings were not endowed with such an operation, they would not be able to reason abstractly. Without analyzing, abstracting, and judging when they reached correct conclusions, human beings would have been given reasoning in vain:

[S]ome exercise of judgment is necessary in the formation of all abstract and general conceptions, whether more simple or more complex; in dividing, in defining, and in general, in forming all clear and distinct conceptions of things, which are the only fit materials of reasoning. (EIP VI. 1, p. 413)

Some authors argue that judging should not be understood as involving just mental affirming or denial of its content, since that would not distinguish judging from believing. Although Reid’s official characterization of judgment is meant to clarify how this mental operation accompanies all others, belief already implies a mental assent/dissent given to its content. In the picture Reid is putting forward, there seems to be no way to explain why somebody would assent (dissent) to something without that person’s already having a belief that it is true (or false). Judgment, therefore, seems to presuppose belief. Judgment, then, would simply be superfluous, while belief would be ubiquitous, either as a concomitant or an ingredient in all other operations of the human mind (Rysiew (2004): 65). This, however, contradicts Reid’s official characterization of judgment:

[A] man who feels pain, judges and believes that he is really pained. The man who perceives an object, believes that it exists, and is what he distinctly perceives it to be; nor is it in his power to avoid such judgment. And the like may be said of memory, and of consciousness. Whether judgment ought to be called a necessary concomitant of these operations, or rather a part or ingredient of them, I do not dispute. But it is certain, that all of them are accompanied with a determination that something is true or false, and a consequent belief. If this determination be not judgment, it is an operation that has got no name; for it is not simple apprehension, neither is it reasoning; it is a mental affirmation or negation; it may be expressed by a proposition affirmative or negative, and it is accompanied with the firmest belief. (EIP VI. 1, p. 409)

To save Reid from this inconsistency, some have argued that the distinctive character of judgment emerges not from his official characterization of this mental operation, but rather from his comparing it to an external, real-life tribunal. This analogy is not perfect, and per Reid’s instructions (EIP I. 4, p. 55), people should not be lulled into a sense of confidence that they really know what they are talking about when they invoke analogous thinking, especially with regard to analogies concerning the body—or all things external—and mind—or all things internal. However, people are entitled to use the same name—“judgment”—to refer to both the process that results in an assenting/dissenting opinion in a court of law, and to the one that results in an assenting/dissenting belief in the internal tribunal, in virtue of the process involving reasoned reflection and deliberation. The fundamental characteristic of judgment in Reid’s system is its deliberative/reflective character, and not its relation to assent or dissent, which is, in turn, reserved for belief (Rysiew (2004): 67).

ii. Common Sense

Reid argues that sense and judgment are intrinsically related, such that sense always implies judgment: “A man of sense is a man of judgment” (EIP VI. 2, p. 424). He believes this to hold true both for what he calls “the external senses” (for instance, touch, taste, sight) and for the so-called “internal senses” (for instance, moral sense and internal taste). Since Reid believes (mistakenly, as it was discussed above) that judgment is the operation of the mind that helps people determine, “concerning any thing that might be expressed by a proposition, whether it be true or false” (EIP VI. 3, p. 435), and since he talks about common sense in the Essay dedicated to illuminating the nature of judgment, it should be obvious that he thinks that common sense is a specialized kind of judgment, understood as a faculty of the human mind. To wit, Reid thinks that common sense is that minimal degree of understanding that every adult human being possesses (or should possess), such that he can function well in this world. Common sense is concerned only with propositions that express self-evident truths (or falsehoods); judgment, more generally, is concerned with propositions that express any other kinds of truths or falsehoods.

Reid believes that self-evident principles are at the foundation of any kind of knowledge and that common sense is the mental operation that discovers such principles for human beings:

All knowledge, and all science, must be built upon principles that are self-evident; and of such principles, every man who has common sense is a competent judge, when he conceives them distinctly. Hence it is, that disputes often terminate in an appeal to common sense. (EIP VI. 2, p. 426)

This suggests that Reid thinks that human beings are all endowed with a mental operation—common sense—that is meant to discover the first principles upon which any kind of science is built. These first principles, when considered distinctly, namely in isolation from anything else, will be immediately found to be true, just as anything parading as a first principle, when considered distinctly, will be found to be false. No one undergoes a complicated reasoning procedure to discover the truth (or falsehood) of such principles; everyone just knows this, because, in being self-evident, these principles wear their truths conspicuously. In other words, what results from exercising the faculty of common sense is intuitive knowledge. Reid explains that reason and common sense do not conflict, because common sense is part of reason, just as judging does not oppose reason:

We ascribe to reason two offices, or two degrees. The first is to judge of things self-evident; the second to draw conclusions that are not self-evident from those that are. The first of these is the province, and the sole province of common sense; and therefore it coincides with reason in its whole extent, and is only another name for one branch or one degree of reasoning. (EIP VI. 2, p. 433)

Deduction from true principles can never contradict common sense, since “truth will always be consistent with itself” (EIP VI. 2, p. 433).

iii. First Principles of Common Sense

Reid thus believes that human beings are endowed with a faculty that gives them immediate knowledge of self-evident principles. He calls this faculty “common sense,” but it is more common to refer to the results of employing this faculty by the name of “intuitive knowledge.” The main idea here is that such knowledge of first principles is widespread: for instance, people are said to intuit axioms in mathematics and in logic; they also are thought to intuit first principles in morals, just as they intuit first principles regarding the expression of beauty in the arts, Reid believes. This knowledge is not innate; after all, as an Empiricist, Reid thinks that all knowledge is acquired. The faculty of common sense, just like all the other original faculties, is innate, in the sense that they are part of the mental architecture of a human being. The sense in which this intuitive knowledge is immediate, without it being innate is the following: once reasoning and the ability to process a human language are sufficiently developed, a human being will be able to know, non-inferentially, that certain propositions, when considered distinctly, are true.

Reid calls such propositions first principles, and he argues that they can be divided into two classes: first principles of contingent truths, on the one hand, and first principles of necessary truth, on the other. As Van Cleve (1999) points out, just because the former type of principles have contingent truths as their contents, this does not mean that the principles themselves are, in any way, less necessary than those of necessary truths. It is the truths themselves that are either necessary or contingent:

The truths that fall within the compass of human knowledge, whether they be self-evident, or deduced from those that are self-evident, may be reduced to two classes. They are either necessary and immutable truths, whose contrary is impossible, or they are contingent and mutable, depending upon some effect of will and power, which had a beginning, and may have an end. (EIP VI. 5, p. 468)

Since this article is concerned with the main tenets of Reid’s philosophy of mind, first principles are interesting for this purpose only in as much as they are discovered by a faculty—common sense—with which every human being is supposed to be endowed, and they will not be discussed in more detail.

iv. Reasoning

If the first principles of common sense are discovered by employing the operation of intuitive judging, reasoning proper is to be employed to discover whatever conclusions follow from self-evident principles. Since there are two classes of first principles, Reid argues that there are two types of reasoning. Demonstrative reasoning is employed to draw conclusions that follow from the first principles of necessary truths, whereas probable reasoning is employed to draw conclusions that follow from the first principles of contingent truths (EIP VII. 3, p. 556).

The strength of demonstrative reasoning, which is commonly employed in mathematics and logic, is such that for showing that a conclusion follows from some axioms (or first principles) nothing else needs to be done other than offering one demonstration. Reid thinks that it would be superfluous to try to give several different demonstrations to prove one conclusion, while employing demonstrative reasoning, even though a variety of proofs may be available in practice:

To add more demonstrations of the same conclusion, would be a kind of tautology in reasoning; because one demonstration, clearly comprehended, gives all the evidence we are capable of receiving. (EIP VII. 3, p. 556)

It is not so with probable reasoning:

The strength of probable reasoning …depends not upon any one argument, but upon many, which unite their force, and lead to the same conclusion. Any one of them by itself would be insufficient to convince; but the whole taken together may have a force that is irresistible, so that to desire more evidence would be absurd. (EIP VII. 3, p. 556)

Probable reasoning is the method of choice for all the natural sciences, whose true propositions are contingent. According to Reid, probable reasoning comes in degrees, whereas demonstrative reasoning does not admit degrees; it is absolute.

In every step of demonstrative reasoning, the inference is necessary, and we perceive it to be impossible that the conclusion should not follow from the premises. In probable reasoning, the connection between the premises and the conclusion is not necessary, nor do we perceive it to be impossible that the first should be true while the last is false. (EIP VII. 1, p. 544-45)

Although Reid argues that probable reasoning is of a different kind than demonstrative reasoning (EIP VII. 3, p. 557), according to Lehrer (1989: 174), probable reasoning can lead to conclusions that are certain. Reid thinks that the vulgar is mistaken when contrasting probable reasoning with certainty. Probable reasoning, according to Reid, has degrees of evidence, “from the very least to the greatest which we call certainty” (EIP VII. 3, p. 557).

Hume, in the Treatise, argues that all knowledge should be reduced to probability, because human beings are fallible creatures, endowed with fallible faculties. Reid’s understanding of probable reasoning as a type of reasoning that leads to certain conclusions constitutes a direct refutation of Hume’s argument. The problem, Reid points out, is that requiring a proof of the reliability of the human faculties would be circular, because it could be given only by using those reasoning powers themselves, “and is therefore that kind of sophism which Logicians call petitio principii” (or “begging the question”) (EIP VII. 4, p. 571). Hume writes that “[n]ature, by an absolute and uncontrollable necessity, has determined us to judge, as to breathe and feel” (Hume, Treatise I.iv.1, p. 183). Reid agrees with Hume in part: probable reasoning concerning cause and effect, for instance, is the result of an innate principle of human constitution. Such a principle is known to be true, by intuition, and by exercising the faculty of common sense. But Reid also disagrees with Hume, and points out that probable reasoning concerning cause and effect is not merely a matter of custom. The relevant first principle of contingent truth allows human beings to be certain that effect follows its cause, not because they reason that it is so, but because they judge (intuitively) that it is so.

5. Taste

Reid considers the principles of the so-called “internal taste” in Essay VIII, the last of the EIP. Contemporary philosophy of mind is mostly silent concerning the way human beings interact and appreciate works of art; the widespread belief seems to be that such issues belong to value theory rather than to the philosophy of mind proper. Reid, however, is part of a different tradition, which sought to explain the interest humans have in art and its artifacts, and consequently the interactions humans seek with said artifacts starting by observing human psychology. As such, he, just like some of his predecessors (for example, Hume, Hutcheson, and Shaftesbury), thinks that adult human beings are endowed with a special faculty, taste, which is supposed to help them appreciate beautiful or aesthetically relevant things, and disapprove those that are found to be lacking the sought-after qualities. Reid is thus mostly describing and analyzing the aesthetic experience, rather than addressing issues that are relevant from the point of view of the philosophy of art. In the course of doing this, however, he is interested in questions pertaining to art and artworks. Reid has an expression theory of art, in that he is interested in how art can express emotion, or, better still, how artists can and do express emotions through an artistic medium. If art is a sort of language, the faculty of taste, as applied to the aesthetic qualities of artworks, is the way to be made privy to this language: by employing this faculty, human beings become sensitive to the signs and decode their meaning. However, this is not the only way people employ their internal sense: by using this faculty they also become sensitive to the aesthetic qualities of the world. Reid’s idea is that just like a painter is expressing an emotion in his works, God is expressing certain emotions in his works. One cannot gain complete knowledge of the external world, in this picture, unless one understands and appreciates the beauty of the world.

a. Why This Faculty Is Called “Internal Taste”

This name indicates that the faculty itself is of the same kin as the other type of taste, but in what sense is it “internal”?  To better understand this, consider the distinction that Reid draws between things internal and things external to the mind at the beginning of the EIP:

When…we speak of things in the mind, we understand by this, things of which the mind is the subject. Excepting the mind itself, and things in the mind, all other things are said to be external. (EIP I. 1, p. 22)

This distinction is as elucidating as it is confusing: since both types of taste are operations of the mind, they both are, in a sense, internal. However, Reid’s idea is that the “external taste” is supposed to help those beings that have it register information about certain pleasing and displeasing qualities of food and drink. The objects that can be food and drink are external to the mind—they are physical things to be found in the world. So, by analogy, it should probably be thought that “the internal taste” is supposed to help those beings that are endowed with it register information about certain pleasing and displeasing qualities of internal objects—namely, minds and their qualities.

Reid does not argue that other minds can be directly perceived, but he takes it to be a first principle of common sense that other minds exist (the 8th first principle of contingent truths, EIP VI. 5, p. 482-483), and that people learn of their existence by correctly deciphering certain signs. This interpretation of natural signs is innate, since, Reid claims, even small children respond in the correct (that is, expected) way in the presence of an angry parent, for instance. In this picture, the internal sense of taste is meant to discern the quality of excellence that other minds possess, in addition to enhancing the knowledge people have of “the existence of life and intelligence in our fellow-men.” To do so, however, the internal taste orients itself to material objects (since it cannot directly interact with other minds), and identifies that which is beautiful, in nature and in the fine arts (EIP VIII. 1, p. 573).

b. An Objectivist Account of Beauty

Putting everything together, here is the picture that emerges: Reid believes that beauty is a property both of objects and of minds. Moreover, he thinks that beauty itself is both a primary and a secondary quality of objects. Reid’s claim that beauty is a real property of objects directly opposes the idea that beauty is just a feeling in an agent’s mind, advanced by Hume and Hutcheson. As in morals, in the domain of aesthetic value, Reid is an objectivist (at least, according to Benbaji (1999)). The aesthetic (or internal) taste has the dual role of discovering what material objects are beautiful, and, indirectly, what minds, which created those beautiful objects, are inherently beautiful. Beauty, in this picture, is not a feeling in one’s mind, but something external to one’s mind. The internal taste is used to reach aesthetic judgments by evaluating material objects, which express the mental attributes of the artist. Without excellence in the mind, no product of that mind can be perceived as beautiful. Beauty is thus a property of the artist’s mind, and is displayed by the artifacts he creates only in a derivative sense. The internal taste functions very much like perception of external objects: certain signs of aesthetic qualities function to trigger a conception and belief in the existence of the aesthetic quality in question. The internal taste is thus assimilated to the external sense of taste, since both senses are supposed to contribute to the perception of specific qualities of objects.

6. References and Further Reading

a. Primary Sources

  • Hume, D. (2007). A Treatise of Human Nature. Oxford: Clarendon Press. (Original work published in 1739-40.)
    • The standard edition of Hume’s Treatise.
  • Hume, D. (1874-75). “Of the Standard of Taste,” in vol. 3 of The Philosophical Works of David Hume. Edited by T. H. Green and T. H. Grose. 4 volumes, London: Longman, Green.
    • Hume considers whether there can be any objective standard of taste.
  • Hutcheson, F. (2004). An Inquiry into the Original of Our Ideas of Beauty and Virtue. Edited by W. Leidhold. Indianapolis: Liberty Fund. (Original work published in 1726.)
    • This presents Hutcheson’s sentimentalist understanding of beauty.
  • Locke, J. (1979). An Essay Concerning Human Understanding. Oxford: Clarendon Press. (Original work published in 1700.)
    • This is the standard edition of Locke’s Essay.
  • Reid, T. (1997) An Inquiry into the Human Mind on the Principles of Common Sense. Edited by Derek R. Brookes. Edinburgh, UK: Edinburgh University Press. (Original work published in 1764.)
    • This is the standard edition of Reid’s Inquiry. Cited in text as IHM, chapter, section, page number. Cited in text as Essay, book, chapter, section number.
  • Reid, T. (2002) Essays on the Intellectual Powers of Man—A Critical Edition. Edited by Derek R. Brookes. Edinburgh, UK: Edinburgh University Press. (Original work published in 1785.)
    • This is the standard edition of Reid’s work on the intellectual powers. Cited in text as EIP, essay, chapter, page number.
  • Reid, T. (2010) Essays on the Active Powers of Man—A Critical Edition. Edited by Knud Haakonssen and James A. Harris. Edinburgh, UK: Edinburgh University Press. (Original work published in 1788.)
    • This is the standard edition of Reid’s published work on action theory.

b. Secondary Sources

  • Alston, W. P. (1989). “Reid on Perception and Conception.” In M. Dalgarno, & E. Matthews (Eds.) The Philosophy of Thomas Reid, (pp. 35–47). Dordrecht: Kluwer.
    • Argues that conception, despite its name, does not involve the use of any concepts.
  • Benbaji, H. (1999). “Reid’s View of Aesthetic and Secondary Qualities.” Reid Studies 2, 31-46.
  • Buras, T. (2005). “The Nature of Sensations in Reid.” History of Philosophy Quarterly, 22(3), 221–238.
    • Interprets Reid as saying that sensations are reflexive acts of the mind, taking themselves as objects.
  • Buras, T. (2008). “Three Grades of Immediate Perception: Thomas Reid’s Distinctions.” Philosophy and Phenomenological Research, 76(3), 603–632.
    • Explains that there are three senses of “immediacy,” in Reid, making clear the connection between immediacy and original perception, and acquired perception.
  • Buras, T. (2009). “The Function of Sensations in Reid.” Journal of the History of Philosophy, 47(3), 329–353.
    • Explains what function sensations perform: primarily, they give sentient beings information about how they react to the environment.
  • Copenhaver, R. (2000). “Thomas Reid’s Direct Realism.” Reid Studies, 4(1), 17–34.
    • Explains Reid’s account of perception, classifying it as direct realism.
  • Copenhaver, R. (2004). “A Realism for Reid: Mediated but Direct.” British Journal for the History of Philosophy, 12(1), 61–74.
    • Explains the intermediary role of sensations in the chain of perception.
  • Copenhaver, R. (2010). “Thomas Reid on Acquired Perception.” Pacific Philosophical Quarterly, 91(3), 285–312.
    • Offers a compelling argument to show that acquired perception is indeed a form of perception, and not reasoning.
  • Copenhaver, R. (2006a). “Thomas Reid’s Philosophy of Mind: Consciousness and Intentionality.” Philosophy Compass, 1(3), 279–289.
    • Offers a comprehensive explanation of Reid’s philosophy of mind, centered on the concept of intentionality.
  • Copenhaver, R. (2006b). “Thomas Reid’s Theory of Memory.” History of Philosophy Quarterly, 23(2), 171–187.
    • Discusses the ways in which memory gives people direct knowledge of the past, according to Reid.
  • Copenhaver, R. (2009). “Reid on Memory and Personal Identity.” Stanford Encyclopedia of Philosophy.
    • Offers a comprehensive account of Reid’s theory of memory.
  • Falkenstein, L. (2004). “Nativism and the Nature of Thought in Reid’s Account of Our Knowledge of the External World”. In T. Cuneo, & R. Van Woudenberg (Eds.), The Cambridge Companion to Reid, (pp. 156–179). Cambridge: Cambridge University Press.
    • Explains Reid’s brand of nativism, which allows him to keep fixed certain principles which are dear to the British Empiricists.
  • Falkenstein, L. and Giovanni Grandi (2003). “The Role of Material Impressions in Reid’s Theory of Vision: A Critique of Gideon Yaffe’s ‘Reid on the Perception of the Visible Figure.’’’ Journal of Scottish Philosophy, 1(2), 117-133.
    • Argue that no sensations are involved in the perception of visible figure.
  • Folescu, M. (2015). “Perceiving Bodies Immediately: Thomas Reid’s Insight.” History of Philosophy Quarterly, 32(1), 19–36.
    • Argues that bodies are objects of original perception, despite perceivers’ gaining only relative (that is, not direct) notions of them by the use of their senses.
  • Folescu, M. (2015). “Perceptual and Imaginative Conception.” In Todd Buras and Rebecca Copenhaver (eds.), Mind, Knowledge and Action: Essays in Honor of Reid's Tercentenary, (pp. 52–74). Oxford: Oxford University Press.
    • Argues that Reid should have been sensitive to the fact that conception is not employed in the same manner by the perceptual and by the imaginative systems, respectively.
  • Folescu, M.  “Thinking About Different Nonexistents Of The Same Kind.” Published online first in Philosophy and Phenomenological Research. DOI: 10.1111/phpr.12196
    • Argues that Reid’s account provides the tools for entertaining singular imaginings of different fantastical creatures of the same kind.
  • Gallie, R. (1997). “Reid: Conception, Representation and Innate Ideas.” Hume Studies, 23(2), 315-35.
    • Argues that conception requires linguistic representation.
  • Ganson, T. (2008). “Reid’s Rejection of Intentionalism.” Oxford Studies in Early Modern Philosophy, 4, 245–263.
    • Argues that sensation is not intentional: it is not about any objects, be those objects the sensations themselves.
  • Kivy, P. (2004). “Reid’s Philosophy of Art.” In T. Cuneo, & R. Van Woudenberg (Eds.) The Cambridge Companion to Reid, (pp. 267–312). Cambridge: Cambridge University Press.
    • Argues that Reid is one of the first philosophers interested in philosophy of art, rather than aesthetics, in general.
  • Kivy, P. (1978). “Thomas Reid and the Expression Theory of Art.” The Monist, 61(2), 167–183.
    • Argues that Reid has, primarily, an expression theory of the arts: artworks express the emotions of their creators.
  • Kroeker, E. R. (2010). “Reid on Natural Signs, Taste and Moral Perception.” In S. Roeser (Ed.), Reid on Ethics: Philosophers in Depth, (pp. 46–66). Palgrave Macmillan.
    • Argues that original beauty and other aesthetic qualities are intrinsic qualities of minds.
  • Lehrer, K. (1978). “Reid on Primary and Secondary Qualities.” The Monist, 61(2), 184–191.
    • Presents and defends the distinction between these two types of properties of objects.
  • Lehrer, K. (1989). Thomas Reid. London and New York: Routledge.
    • Offers a comprehensive exposition of Reid’s philosophy.
  • Manns, J. W. (1988). “Beauty and Objectivity in Thomas Reid.” British Journal of Aesthetics, 28, 119–131.
    • Argues that beauty is objective, for Reid, on the principles of common sense, but not objective, on the correct philosophical principles.
  • Nauckhoff, J. C. (1994). “Objectivity and Expression in Thomas Reid’s Aesthetics.” Journal of Aesthetics and Art Criticism, 52, 183–191.
    • Argues that minds are excellent, hence beautiful, and that any other object deemed beautiful has that quality in virtue of being a sign of some excellence.
  • Nichols, R. (2002). “Reid on Fictional Objects and The Way of Ideas.” The Philosophical Quarterly, 52(209), 582–601.
    • Argues that Reid’s rejection of the “way of ideas” leads him to adopt a form of moderate Meinongeanism, before Meinong.
  • Nichols, R. (2007). Thomas Reid’s Theory of Perception. Oxford: Oxford University Press.
    • Analyzes the major tenets of Reid’s theory of perception.
  • Pappas, G. S. (1989). “Sensation and Perception in Reid.” Noûs, 23(2), 155–167.
    • Defends the distinction between sensation and perception in Reid; a classic piece in Reid studies.
  • Rysiew, P. (1999). “Reid’s [Mis]charaterization of Judgment.” Reid Studies 3(1), 63–68.
    • Argues that, despite his official characterization, “judgment,” for Reid, should be understood to mean reflection.
  • Tulving, E. (1983). Elements of Episodic Memory. Oxford: Oxford University Press.
    • Explains what types of memory there are, and why episodic memory is fundamental.
  • Van Cleve, J. (1999). “Reid on the First Principles of Contingent Truths.” Reid Studies 3, 3–30.
    • Argues that the first principles of contingent truths allow Reid to be a reliabilist with regard to the cognitive faculties of human beings, without any kind of circularity.
  • Van Cleve, J. (2004). “Reid’s Theory of Perception.” In T. Cuneo, & R. Van Woudenberg (Eds.) The Cambridge Companion to Reid, (pp. 101–133). Cambridge: Cambridge University Press.
    • A comprehensive account of Reid’s theory of perception, with special care given to identifying Reid’s type of realism: direct or indirect. This is the best starting point for anyone interested in getting a better understanding of Reid’s theory of perception.
  • Van Woudenberg, R. (1999). “Thomas Reid on Memory.” Journal of the History of Philosophy, 37(1), 117–133.
    • Discusses the elements of Reid’s theory of memory.
  • Van Woudenberg, R. (2004). “Reid on Memory and the Identity of Persons.” In T. Cuneo, & R. Van Woudenberg (Eds.) The Cambridge Companion to Thomas Reid, (pp. 204–221). Cambridge: Cambridge University Press.
    • Discusses the role of memory in personal identity.
  • Wolterstorff, N. (2001). Thomas Reid and the Story of Epistemology. Cambridge: Cambridge University Press.
    • Explains Reid’s terminology and way of thinking such that contemporary epistemologists can see Reid as an exponent and precursor of some of the issues discussed today.
  • Yaffe, G. (2003a). “The Office of an Introspectible Sensation: A Reply to Falkenstein and Grandi.” Journal of Scottish Philosophy, 1(2), 135–140.
    • Responds to the criticisms raised by Falkenstein and Grandi to the idea that all kinds of perceptions, including the perception of visible figure, involve sensations.
  • Yaffe, G. (2003b). “Reid on the Perception of Visible Figure.” Journal of Scottish Philosophy, 1(2), 103–115.
    • Argues that perceiving the visible figure of objects, for Reid, involves having sensations of color.


Author Information

Marina Folescu
University of Missouri
U. S. A.

1. Philosophical Method

1.1 Common Sense and First Principles

Reid often articulates his theoretical positions in terms defending common sense and the “opinions of the vulgar”. Indeed, he is often described as a “common sense philosopher”. This reputation owes less to the philosophical uses Reid makes of common sense than to fellow Scotsman James Beattie, who popularized common sense in his very widely read An Essay on The Nature and Immutability of Truth In Opposition to Sophistry and Scepticism (1770). Even today it is easy to overestimate and to misunderstand the role of common sense in Thomas Reid's philosophical system.

The most important use of the term “common sense” in Reid occurs in the context of his epistemology and his philosophical method. Here it refers to a select set of intuitive judgments. Reid calls these variously “first principles, principles of common sense, common notions, [or] self-evident truths” (Essays on the Intellectual Powers, abbreviated ‘EIP’, 6.4, 452). Common sense first principles are identifiable because they typically possess a suite of additional traits (traits, note, not necessary conditions) as follows. Denial of a common sense principle is not only false but absurd (EIP 6.4, 462). A common sense judgment is “necessary to all men for their being and preservation, and therefore it is unconditionally given to all men by the Author of Nature” (EIP 4.6, 412). Common sense intuitive judgments are “no sooner understood than they are believed. The judgment follows the apprehension of them necessarily, and both are equally the work of nature, and the result of our original powers” (EIP 6.4, 452).

Common sense principles possess “the consent of ages and nations, of the learned and unlearned, [which] ought to have great authority with regard to first principles, where every man is a competent judge” (EIP 6.4, 464). Common sense principles are common sense because, but not only because, they are common to humanity. Reid's account of common sense does not itself approach the status of a philosophical or psychological theory. Though his commitment to common sense forms a key component in his philosophical method, a deeper methodological principle clearly underlies his appeal to common sense. Reid attempts to build his fallibilist, foundationalist account of empirical knowledge while working under an empiricist constraint that prohibits speculative use of a priori reason. As a result, Reid's reference to beliefs held in common across time and place, across culture and religion, functions as an empirically justified generalization about species-typical features of human cognition.

Though this marks a point commonly neglected in the interpretation of Reid, one can often find, in his discussion of common sense, emphasis on empirical generalizations from observable data about what people believe and how they behave. For example, he writes, “The universality of these opinions, and of many such that might be named, is sufficiently evident, from the whole tenor of human conduct, as far as our acquaintance reaches, and from the history of all ages and nations of which we have any records” (EIP 6.4, 466). Laying stress upon his claim about the universality of certain beliefs across our species has opened Reid up to tiresome criticism that began in his lifetime and continues to the present of the following sort: Reid's appeals to common sense are little more than affirmations of majority opinion or appeals to the masses, but these are fallacious, so his inferences from such principles are defeated. Reid corrects this misunderstanding by emphasizing the fact that his first principles are psychological generalizations about belief formation applicable to most of our species (EIP 6.4, 464–5).

Reid often appeals to the structure of languages as evidence for generalizations about human cognition, belief, and descriptive metaphysics. Language, being something so widely shared, offers an abundance of data for observation. Reid finds many commonalities across languages. (The connection between ordinary language and common sense that Reid espouses was of great influence on such later philosophers as G. E. Moore and J. L. Austin.) Reid does not believe, however, that every feature of ordinary language is indicative of some important tenet of common sense (EIP 1.1, 26–27). Reid often suggests that the relevant features are those that can be found in “the structure of all languages”, suggesting that the linguistic features of relevance are features of syntactic structure shared among languages. Reid says there is some important difference between the active and the passive, since “all languages” have a passive and active voice. All languages distinguish between qualities of things and the things themselves (EIP 6.4, 466). This suggests that certain universal features of the syntactic structure of languages inform us of a common sense cognitive commitment, even if it is implicit.

Most of Reid's first principles of contingent truth take the form of Principle 5, which reads “That those things do really exist which we distinctly perceive by our senses, and are what we perceive them to be” (EIP 6.5, 476). Such common sense first principles are intended to be more than merely generalizations about how humans across cultures form beliefs. Reid intends these general principles to provide evidence for particular beliefs. Thus Principle 5 issues in the self-evident belief, for example, that I perceive a computer before me (Van Cleve 1999). As a result, Reid's philosophical method accords with common sense insofar as everyday perceptual beliefs are evident or self-evident.

An implication of Reid's application of his common sense method to first principles is that Reid is not concerned to answer questions of justification that appear pressing to contemporary epistemologists. He is not, for instance, interested in providing a refutation of skepticism about the external world by appeal to first principles. Reid believes he can refute skeptical hypotheses--such as Descartes's hypothesis of an evil demon who makes us believe that the world is the way we take it to be when it is really vastly different--simply by showing that such a hypothesis is no more likely to be true than the common-sensical belief that the world is much the way we perceive it to be. Since the belief in the external world is a dictate of common sense, it is, Reid thinks, as justified as it needs to be when it is shown to be on the same footing as any alternative. Justification, therefore, does not necessarily require providing positive reasons in favor of common-sensical beliefs; common sense beliefs could be adequately justified simply by undermining the force of the reasons in favor of alternatives to common sense. In fact, as we move through this entry, we will witness Reid's repeated deployment of this strategy in the form of burden-of-proof arguments against his major foil, the Way of Ideas. Common sense constrains, rather than dictates, acceptable philosophical positions.

A number of additional problems remain in accounting for Reid's appeal to common sense and in his treatment of first principles. For example, a number of comments Reid makes indicate that he appears to have a psychological conception of evidence whereby what is evident forces assent. He writes, “[The different kinds of evidence] seem to me to agree only in this, that they are fitted by nature to produce belief in the human mind” (EIP 2.20, 292). Just what he means, then, by terms “evident” and “self-evident” (terms he greatly prefers to the more contemporary “justification” and “knowledge”) is an issue meriting further research.

1.2 Newtonianism and Empiricism

The relations between one's first principles, the perceived aims—and limits—of natural philosophy, and one's religious background came together in eighteenth-century Great Britain to issue in a number of different philosophical stances. Typically these stances are framed as various commitments to Newton and Newtonianism. Hume and MacLaurin believe the mind's operations are to be studied with broadly observational Newtonian methods, though this leads them to forms of local skepticism. Priestley and Hartley apply Newtonianism not only to the operations of the mind but to the mind's substance via materialist commitments. Reid's teacher George Turnbull adopted Newtonianism and was led to Berkeleyan idealism by many of Berkeley's own common-sense commitments. Wanting both the world and knowledge of it in his philosophical system, Reid was at pains to articulate his account of both common sense and Newtonianism. Unlike most British Empiricists, Reid read, understood, and taught Newton's writings. To understand Reid's philosophical method, not to mention his philosophy of science, one must understand core features of Reid's Newtonianism (Callergård, 2010) and, perhaps, how Reid altered Newton's own method (Ducheyne 2006).

First, Reid is committed to the positive role of mathematics in stating and testing theories. Only in that field do we “find no sects, no contrary systems, and hardly any disputes” (EIP 6.4, 457). Newton's greatness lies in part due to the fact that he places physics upon firm mathematical ground, in sharp contrast to Cartesian physics, its leading competitor of the time. Second, Reid says that issues about causation are not issues physics should attempt to resolve. This counterintuitive commitment is explained by the fact that Reid believes causes, when that term is used properly, are efficient causes (The Correspondence of Thomas Reid, abbreviated ‘Correspondence’ below, 2006, 158). Not only this, efficient causes are only ever agents (EAP 1.5, 30–32; for more about this, see 4. Causation and Free Will, below). Reid attributes this position to Newton. Reid mentions on many occasions, and with a certain pride, that Newtonian science does not permit knowledge of causes of phenomena, for example, the motion of the compass needle or the attraction of two bodies. Here and elsewhere Reid frequently speaks with the scientists and uses ‘cause’ in a colloquial way to refer to physical causes; in doing so, he explicitly follows David Hume's lead. More often, however, Reid urges readers to think of scientific explanation in terms of laws, as Newton had done. Laws are true general propositions used to explain appearances (Thomas Reid on the Animate Creation 1996, 187). Physics does not aim to find efficient causes. By dispensing with causes and amplifying the explanatory value and empirical justification of statements of laws, Reid's account is regarded as a forerunner to a deductive-nomological model of explanation.

Third, related, when one event produces another event, e.g. fertilizer enables better plant growth, Reid strongly resists describing that interaction as necessary (The Correspondence of Thomas Reid 2006, 234, 243). One event may be constantly conjoined to another event, but it is a mistake to believe that this forms any necessity. Fourth, unlike nearly all other Early Modern philosophers traditionally taught in the canon, Reid was an avowed experimentalist, made so by borrowing Newton's methods in Opticks, and conducted experiments to provide evidence for his claims about the nature of the mind, perception and agency. Reid was active in his community, bringing his penchant for knowledge through experimentation to meetings in Aberdeenshire in which experimental techniques in farming were debated. Fifth, Reid understands Newtonian physics to offer partial confirmation to some beliefs about God and God's relation to the world. Newtonian natural science's role in this connection is to provide evidence for belief that our solar system is orderly and well-governed. (See 8. Philosophy of Religion below).

Stating central features of Reid's commitment to Newtonianism goes a long way to understanding Reid's empiricism and science since Reid attributes most of his own views about these matters to Newton. Despite the fact that with a few notable exceptions Reid scholars have neglected issues in his philosophy of science, a few key controversies have emerged and merit brief mention. First, Reid was embroiled in clashes with other thinkers and correspondents about the scope of Newton's Regulae Philosophandi. Interpretations differed considerably, as did the translations and restatements of the rules themselves. Given that after Bacon's work, Newton's Regulae formed the most important statement on method in natural philosophy to be found in the Early Modern period, Reid was quick to defend his interpretation of these rules against alternate uses by Priestley and others.

Reid translates Newton's first rule from Latin as “No more causes, nor any other causes of natural effects ought to be admitted, but such as are both true, and are sufficient for explaining their appearances” and adds in his own voice, “This is a golden rule; it is the true and proper test, by which what is sound and solid in philosophy may be distinguished from what is hollow and vain” (EIP 1.3, 51). Reid expands the intended scope of this rule saying that it is a “fundamental principle in our enquiries into the structure of the mind, and its operations” (EIP 1.3, 51). Occurring in the introductory portion of his Essays on Intellectual Powers, he would go on to use and reuse it countless times in what followed. He also describes Newton's first rule as “a dictate of common sense” (EIP 2.6, 102). Proponents of the Way of Ideas fail to abide by Newton's first rule when they endorse the existence of ideas because the existence of ideas is an hypothesis and lacks evidence.

Another area of controversy in Reid's empiricism involves the grounding of his belief to the effect that ether does not exist. Ether appears to represent just the sort of posit (originally by Descartes in Principles of Philosophy) that Newtonians often enjoyed sweeping into the trash. Lacking any observational evidence for ether, Descartes posits ether as a medium through which forces can act on bodies that are not in direct contact. But does Reid reject ether theory on the grounds that it is unobservable and therefore does not belong in a Newtonian science, or does he reject ether theory because scientists as yet lack justificatory observations on its behalf? Reid's apparent hostility to “hypotheses” in philosophy and “efficient causes” in natural philosophy gives rise to the belief that Reid does not believe that forces should be allowed into philosophy. The answer to this question can resolve that issue and assist in locating Reid's philosophy of science on the positivist/realist spectrum.

The first rule does not entail that unobservables like ether, subtile fluids, or forces do not or cannot have explanatory force, let alone that unobservables do not exist. Reid is explicit that questions about the existence of ether were open questions that were not settled by a priori (EIP 2.3, 82). Physical forces and causes do exist and may yield their secrets to science in the form of purely physical forces of attraction (An Inquiry into the Human Mind on the Principles of Common Sense, abbreviated to ‘IHM’, 7, 211). This has two corollaries of considerable importance for understanding Reid's methods. First, the fact that Reid admits that these forces of attraction—unobservable, immaterial forces—may be physical implies that he is comfortable with a physical explanation of gravitation that does not entail the existence of God. Second, physical forces will not yield their secrets to an impoverished Cartesian science. This criticism is made on the grounds that Cartesians were attempting to understand gravitational attraction in terms of only extension, figure and motion—for Reid, a catastrophic mistake. In fact, Reid's criticism of the Cartesians has provided a clue for an account of Reidian forces as irreducible properties of matter (Callergård 2005, 2010).

2. Conception

Reid's theory of conception is at the heart of his philosophical system and his faculty psychology. The term ‘faculty psychology’ refers, at least for Reid, to both the distinction of certain belief-forming systems from others, and the explanatory utility purchased with such a set of distinctions. While faculty psychology appears to be an obvious way to scientifically study the senses, Reid's study of intellectual powers—memory, judgment, abstraction—under the umbrella of faculty psychology was not obvious. Reid would face pointed criticism for multiplying faculties, but this consequence was more than outweighed by the explanatory utility of separating mental powers—their inputs, their operations, and their outputs—from one another.

The most ubiquitous mental power is that of conception. Our suite of intellectual faculties supports a wide variety of mental events. Acts of conceiving are embedded in most of them. Whether judging that there is a tree before me, imagining there is a tree before me, or reasoning to a generalization that all trees have roots, these mental events employ the faculty of conception. It is in virtue of conception that the first of these mental states is about the proposition there is a tree before me; that the second mental state takes as its object a non-existent tree; and that the third uses a general conception of ‘tree’. The Way of Ideas teaches, wrongly, that acts of perception temporally begin with an act of simple apprehension “and that after we have got simple apprehensions, by comparing them together, we perceive agreements or disagreements between them,” but, Reid continues, “this appears to me to be all fiction, without any foundation in nature” (IHM 2.4, 29). Instead, simple apprehension—the basic form of conception—is bundled within typical acts of perception. The model of conception received from the Way of Ideas marks its first long step into two types of skepticism.

Note that the set of commitments that Reid refers to as “The Way of Ideas” and the “Ideal Theory” is drawn form the work of Locke, Berkeley, Hume and many others going back to Plato and Aristotle. Its principle commitment is to mental representations, called ‘ideas’ or ‘images’, that are believed to mediate all our experience of the world—from conception to memory and perception. Reid regards the Way of Ideas as founded on a flawed, anti-Newtonian methodology, is unscientific, and he argues that it has highly undesirable consequences.

2.1 Conceiving

Conception lies at the heart of the operations of the intellectual faculties because conception provides the intentional content—the ‘aboutness’—to mental states. Reid distinguishes between several functions of conception. A rudimentary form of conceiving, which Reid often calls ‘simple apprehension,’ refers to “the bare conception of a thing without any judgment or belief about it” (EIP 4.1, 295). This “enters as an ingredient in every operation of the mind” (EIP 4.1, 296). In order to believe, or remember or perceive, I must perform an act of simple apprehension in order to get something in mind.

We explain Reidian conception by contrast with the Way of Ideas. First, Reid presupposes that the mind has an irreducible capacity for intentional conception in which our mental states are uniquely about specific objects. This faculty cannot be explained in terms of further non-intentional states. How intentional conception can be explained is mysterious—Reid is well aware of this. Yet if “we were unable to give any account how we first got the conception of power, this would be no good reason for denying that we have it” (Reid 2001, “Of Power,” 5). In a contrasting methodological move, Hume suggests that intentional content through ideas is built up from the operation of the laws of association—contiguity in time and space, resemblance and perceived causation—working upon impressions and images in the mind (see Treatise, 4;, 33;, 319; Enquiry 7.2.6, 74).

Conception takes as its intentional objects items with varied ontologies, including physical objects and propositions (EIP 1.1, 24–5) as well as fictional beings like Brienne of Tarth. The fact that conception takes physical objects as (direct) intentional objects marks a key contrast with the Way of Ideas since, on the Way of Ideas, conception, perception, judgment and belief are “only different ways of perceiving ideas in our own minds” (EIP 4.1, 298). (Note that, according to Reid, the Way of Ideas fails to adopt a proper faculty psychology since all mental powers—memory, perception, abstraction, etc.—only ever take ideas as intentional objects.) Considerable work in the secondary literature has been devoted to determine just what the content of conceptions are or can be.

The state of conception is not a ‘quantitative’ state for Reid, as are ideas according to Hume, who writes that some ideas are lively, others not, and others partially lively (Treatise 1.1.1). Hume uses these valences to determine which faculty is at work conceiving the idea. If I perceive an idea of a tree, my conception is lively and vivacious. If I remember the same idea of a tree, my conception is faint. Instead, Reid offers an account of a distinct faculty—conception—whose objects are embedded in other acts of the intellectual powers.

Reid's is an act-based theory of conception, in contrast to the Way of Ideas' object-based theory. Conceptions are ways of being aware of objects. To conceive of an object is to be aware of that object as the bearer of some particular property. So I can conceive that Brienne of Tarth is tall, or that Brienne of Tarth is female, or that Brienne of Tarth is a tall female. Being tall and being female are different properties, and their difference signals something important about Reidian conception. Being tall is a relational property since height is a trait that is assessed relative to some further thing or standard. To foreshadow, this subtle feature of conception will become important for Reid in his discussion of vision, especially his discussion of the relational property of visible figure.

2.2 Conception and Self-Knowledge

Reid affirms human beings know what are the intentional contents of their thoughts. If I think about a tree, then I am (defeasibly) justified that I am thinking about a tree. But the Way of Ideas jeopardizes Reid's commitment to the obviousness of our introspective ability to identify what we are thinking about. Like the more familiar veil of perception created by the representational role of ideas (see 3.1 The Way of Ideas and Representational Theories of Perception ), there is also a veil of conception. The seeds of Reid's argument are in Hume's candid remark that, given the Way of Ideas, mental events “seem entirely loose and separate. One event follows another; but we never can observe any tie between them. They seem conjoined, but never connected. ... [T]he necessary conclusion seems to be that we have no idea of connexion or power at all, and that these words are absolutely without any meaning” (Enquiry 7.2.6, 74; see Treatise, 67). Hume's causal explanation of reverberating impacts on impressions in the mind does not explain the content of our thoughts. Hume describes his theory of thought as corpuscular because impressions are atomic and separable mental states without any determinate intentional link to anything else. Note that Hume appears to be led to this position by way of his attempt to repurpose Newtonian mechanics, as it applies to bodies, to formulate a science of the mind.

Troubled by the statement from Hume, Reid constructs a reductio argument against Hume's theory of thought that plays upon the implications just noted. Reid presents this argument about the intentionality of thought through an analogy about the meaning of language, specifically, about someone who is blind to the meaning of the language in a book. Suppose I see unfamiliar ink marks on paper. I neither know what they mean nor even that they are meaningful to anyone. The meanings of these words are not intrinsic to the representations of the words, whether those representations are on paper or are sound waves, just like the intentional content of ideas is not intrinsic to the ideas themselves. Reid writes:

Suppose that ideas represent things like symbols; in this way, words and writing are known to express everything. Let the intellect, therefore, be instructed by ideas ... like a written or printed book, teaching us many things that are external, that have passed away, and that will come to be. This view does not solve the problem; for who will interpret this book for us? If you show a book to a savage who has never heard of the use of letters, he will not know the letters are symbols, much less what they signify. If you address someone in a foreign language, perhaps your words are symbols as far as you are concerned, but they mean nothing to him. (Philosophical Orations, Reid 1937, 35 & Reid 1989, 62)

Uninterpreted impressions are syntactic and purportedly representational. But “Symbols without interpretation have no value” (Philosophical Orations, Reid 1937, 35 and Reid 1989, 62). The resulting veil of conception implies that my impressions risk having no meaning for me. As a result, I do not know the contents of my own thoughts. Since this is absurd, Reid rejects the Way of Ideas' premise that leads to it. This fascinating argument has been explored and its affinities with John Searle's Chinese Room argument have been noted (Haldane 1989, 1993 & Nichols 2007, ch. 2), but it merits further development.

Reid's reductio of the Way of Ideas' theory of thought is intended to buttress Reid's claims that conceiving is irreducibly intentional and that, because of this, we have knowledge of the contents of our thoughts. Hume refrains from this claim in part because he sees no plausible metaphysics to support it. That is, if intentionality is endemic to thought, then the mind must not be what we think it is—a part of nature whose ideas operate on impact principles familiar from Newtonian mechanics. Reid is aware of this problem and prepares to bite the bullet. He describes our ability to apprehend one thing and not another as being “a natural kind of magic” (IHM 5.3, 59–60). In an effort to explicate this mysterious conceptual ability, Reid examines theories of thought of Aristotle and medieval philosophers. These theories posit substantial forms that conjoin thoughts to their intentional objects (Philosophical Orations, Reid 1937, 38 and Reid 1989, 66). Yet Reid judges them harshly and finds their ontology “incomprehensible” (EIP 2.8, 114). He withholds further speculation about the metaphysics that must undergird the claim that intentionality is primitive. This move illustrates a feature of Reid's philosophical method: common sense and knowledge are conceptually and explanatorily prior to metaphysical commitments.

2.3 Abstraction, Universals and General Conceptions

Reid is a nominalist about universals, which means that Reid does not believe that universals exist independently of the set of individual things that instantiate the shared property. (A universal is a property shared by many individuals, each of which instantiates the universal. In addition to opposing arguments for universals, he also opposes the form of nominalism advocated by Berkeley and Hume. Reid concludes that universals are general terms, not abstract or general ideas.

As usual, Reid builds his theory by learning from mistakes of earlier theories. Medieval philosophers argued, by Reid's account, that a universal exists independently of individual things. Some of these philosophers argued that the independent existence of a universal was existence as a form, a venerable philosophical term. Addressing this, Reid says it is impossible that “a triangle should really exist which has no precise proportion of sides and angles” and, generally, it is “impossible that any being should exist which is not an individual being” (EIP 5.6, 396). The principal philosophical error that led to the reification of universal properties as independent existents is the conflation of the objects of conception with the objects of perception (EIP 4.1, 302–3). The metaphysics required to undergird the existence of universals is anathema to Reid's commonsense commitments and his empirical method.

Next Reid considers a theory he associates with Locke, namely that universals do not exist as metaphysical forms but rather universals are abstract ideas. Abstract ideas arise through a process in which facts about time and space are stripped away from particular members of a class of thing leaving the abstract idea that represents common characteristics (EIP 3.2). Reid argues that there can be no such abstract ideas and that abstract ideas cannot represent members of a class of particulars (EIP 5.6, 391–3). Reid recognizes his great debt to Berkeley's criticisms of Lockean abstract ideas in these connections.

In effect, Reid arrives at his own theory by endorsing Berkeley's nominalism and attempting to remove from it reference to ideas. Reid replaces talk of abstract ideas with the term ‘general conception.’ As to the ontology of general conceptions, Reid says that human minds create them, not nature; this reconfirms Reid's nominalism about kind terms. General terms are the linguistic manifestation of general conceptions. General terms are general due to their referents, but they are particular token conceptions of individuals (EIP 5.2, 360). General terms refer to species or to attributes. When we conceive of general terms like ‘lion’ or ‘felony’ or ‘unicorn’, “the meaning of the word is the thing conceived” (EIP 5.2, 364). The term ‘lion’ does not resemble what it is about; it represents the class of lions by convention.

This leads to Reid's explanation of how general conceptions are formed. Reid says this typically happens via induction through testimony and not via definitions (EIP 5.2, 363). For Reid, forming general conceptions is typically a public process and a product of social practices, in contrast to Locke, Berkeley and Hume, for whom forming abstract ideas is typically a private process. (Though we do not enter into discussion of the role of testimony and social knowledge anywhere in this entry, it is especially prominent in Reid.) However, one may also form a general conception on one's own. In this case, in the first stage one analyses a subject into its attributes and names them, which Reid compares to a chemist analyzing a compound (EIP 5.3, 370). Next one observes that similar token attributes are possessed by many objects. Third is “combining into one hole a certain number of those attributes...and giving a name to that combination” (EIP 5.3, 365). The name that results may be the same as the name for a particular attribute, e.g. ‘whiteness,’ but used as a general term, ‘whiteness’ “implies no existence, but may be predicated of everything that is white, and in the same sense” (EIP 5.3, 367). This way of putting the point—that the general term whiteness may be predicated of everything that is white—has inspired a dispositional interpretation of Reidian general conceptions (Castagnetto 1992). Reid's writing on general conceptions and abstraction are areas—like the next topic, conception of non-existent objects—that have not been given much attention.

2.4 Non-Existent Objects

Reid believes that we can conceive of non-existent objects. This does not appear to comport with his alleged common-sense philosophy, creating an interesting conundrum for Reid interpreters. The best approach to understanding why Reid says we can conceive of non-existent objects is to put this in the context of Reid's opposition to skepticism. In the face of ‘veil of conception’ skepticism, Reid is intent on defending the transparency and self-knowledge of our thoughts. This leads him to argue that we can conceive of non-existent, fictional objects: “I conceive a centaur. This conception is an operation of the mind, of which I am conscious, and to which I can attend. The sole object of it is a centaur, an animal which, I believe, never existed” (EIP 4.2, 321; see EIP 2.12, 160). Suppose when I think I am conceiving of a centaur, I am conceiving of something else, like an image of a centaur. If so, then I do not know the contents of my thoughts. This yields skepticism about the contents of my thoughts, which Reid believes is false. So, by reductio he concludes that we are able to conceive of objects that do not exist.

The factual claim that I know what I am thinking appears to be obviously true insofar as anyone familiar with the meaning of ‘centaur’ conceives of centaurs when reading sentences that predicate properties of centaurs. Representational theories of thought like the Way of Ideas imply in this case that I do not conceive of centaurs but rather I conceive of mental representations of centaurs—images of them or words about them (EIP 4.2, 312). But Reid is asserting something different: I conceive of a centaur itself—not a mental representation of a centaur. Appreciating this point is necessary for understanding how strange Reid's theory appears to be.

Reid understands the Way of Ideas' error theory of the conception of a centaur: “The [proponent of the Way of Ideas] says, I cannot conceive a centaur without having an idea of it in my mind.... Perhaps he will say, that the idea is an image of the animal, and is the immediate object of my conception, and that the animal is the mediate or remote object.” Reid first responds that when he introspects he is aware of only one object of conception, not two. Second, the object of conception, he writes,

is not the image of an animal—it is an animal. I know what it is to conceive an image of an animal, and what it is to conceive an animal... The thing I conceive is a body of a certain figure and colour, having life and spontaneous motion. The philosopher says, that the idea is an image of the animal; but that it has neither body, nor colour, nor life, nor spontaneous motion. This I am not able to comprehend. (EIP 4.2, 321–2)

Even in difficult cases of thoughts about things like centaurs or circles (EIP 4.3, 323–4), their intentional contents are so transparent in a moment's reflection that we can identify them without mistake. Reid presses this epistemological point into heavy service in the context of the conception of non-existent objects. As with Reid's appeal to the irreducible intentionality of conception, Reid's position regarding the conception of non-existent objects has proven challenging to explain and to defend, but starts have been made (David 1985–6; Nichols 2002). Though his commitment to the importance of self-knowledge and the transparency of thought is obvious, Reid jeopardizes his allegiance to common sense by asserting we think of non-existent objects directly and without thinking of a mental intermediary.

3. Perception and Knowledge of the World

3.1 The Way of Ideas and Representational Theories of Perception

When discussing Reidian conception, we contrasted Reid's analysis of this faculty with the Way of Ideas'. For Reid, conceptions or ‘simple apprehensions’ possess intentional content in virtue of which these mental states are about other things. Conceptions can be about a wide variety of thing: I can conceive of pain, a shooting pain Descartes' foot, penne, and fictional characters like Podrick Payne. However, according to the Way of Ideas, I can conceive only of one type of thing: Ideas. According to the Way of Ideas, this holds true not only for conception but for all other faculties. If I tactilely perceive a pillow, my perceptual mental state is not about the pillow but rather it is about my idea or mental representation of the pillow. The basic structure of the representational theory of perception (and conception, memory, etc.) is explicitly endorsed by Descartes, Locke, Berkeley, Hume and many other Early Modern philosophers, as well as many living philosophers. We doubt that there is any other philosophical commitment that more exercised Reid's mind than this one, which he thought to be a source of ruin for many reasons. Both Reid and Richard Rorty see the Way of Ideas' representationalism as the key player in the story of Early Modern Western philosophy (Rorty 1981), which would continue as the story of contemporary analytic philosophy.

To the basic structure of the representational theory of perception, one of many components can be added to explain how we are ‘aware’ of external, physical objects even though the immediate object of perception is an idea. Here are three possibilities: (1) we are aware of external objects directly by perceiving representations of them, ideas; (2) we infer the existence and nature of external objects by perceiving ideas of them; or (3) there is no distinction between external objects and ideas, and, thus, when we perceive ideas we are perceiving external objects.

On option (1), the representationalist would need to offer an explanation of what it is that is so special about ideas that makes it the case that whenever we are perceiving an idea, we are directly aware of that which it represents. If this burden can be discharged, then it is possible to say that we are aware of external objects and remain consistent with the representational theory. In the history of philosophy Reid documents a series of failed efforts to explain how it is that perception of something in the mind could amount to any direct perception or awareness of some external object. These attempts make the mistake, he thinks, of giving unexplained and unexplainable powers to ideas: how could they possibly, all by themselves, attach our minds to objects whenever they are perceived? This question cannot be answered, so he thinks.

As to (2), Reid thinks that nobody who has absorbed Hume's lessons regarding causation would think that we can avoid skepticism about the external world while insisting that we infer its nature from the features of directly perceived ideas. On the representational model, external objects are the causes of our ideas. But if Hume is right about causation then we can only infer the nature of a particular unobserved cause of a particular observed effect when we have had repeated experience of conjunction of similar causes with similar effects. But according to the Way of Ideas we have never in fact had any experience of the relevant causes, namely physical objects and their qualities; we have only experienced their effects on our minds, ideas. Therefore, we can infer nothing about external objects by examination of the ideas which they cause in us. Option (2) appears to give skepticism a foothold.

As to (3), Reid believes that it amounts to an endorsement of idealism. Reid finds this theory implausible on its own, and in violation of a host of common sense principles, despite the fact that he admires Berkeley's efforts to pursue its full implications. Reid's arguments against representationalist attempts to recover the awareness of the external world through perception via options (1), (2) and (3) are by no means all of his arguments against the representationalist theory of perception or the Way of Ideas. We now introduce a few additional considerations for which Reid rejects that theory.

3.2 Reid's Arguments Against Representationalism

First, note that proponents of the Way of Ideas commit themselves not only to the existence of ideas but to pressing ideas into a number of functional roles in the mental lives of human beings. But, according to Reid, the underlying rationale for these commitments is typically not even stated by proponents of the Way of Ideas; it is most often taken for granted, or supported with demonstrably weak arguments. As a result, the rationale for commitments to an ontology of ideas and to their functional roles in the mind does not confer upon that commitment much epistemic justification. In the context of a passage in which Reid imagines a dialogue between “the vulgar” or the common person on the one hand and “the philosopher” on the other, Reid develops this reasoning as follows:

When, therefore, in common language, we speak of having an idea of anything, we mean no more by that expression, but thinking of it. The vulgar allow that this expression implies a mind that thinks, an act of that mind which we call thinking, and an object about which we think. But, besides these three, the philosopher conceives that there is a fourth—to wit, the idea, which is the immediate object. The idea is in the mind itself, and can have no existence but in a mind that thinks; but the remote or mediate object may be something external, as the sun or moon; it may be something past or future; it may be something which never existed. This is the philosophical meaning of the word idea; and we may observe that this meaning of that word is built upon a philosophical opinion: for, if philosophers had not believed that there are such immediate objects of all our thoughts in the mind, they would never have used the word idea to express them. (EIP 1.1, 31)

The Way of Ideas philosopher must talk the man on the street out of the belief that “When I perceive an apple in front of me, the apple is the very thing I'm perceiving.” The philosopher's response—that this is a mistake, that the object of perception is an idea of the apple—is predicated upon a rejection of the vulgar's conception of everyday thoughts about objects. But this rejection appears to rest in the opinion of philosophers rather than in the entailment of some as yet unstated but decisive argument. As a result, the rationale for commitments to an ontology of ideas and to their functional roles in the mind appears to Reid to be as dubious, if not more, than the man on the street's original commitment to a direct form of perception. If Reid is correct, then this shifts the burden of proof back upon the advocate of ideas.

Second, in a structurally similar argument, Reid observes something important about the intended explanatory power of the representational theory of perception. That theory is intended to explain the fact that our mental states manage to connect to real objects, manage to be about real objects. However, this fact about beliefs is only explained by the model if the model is less obscure than the phenomena to be explained by it. But, Reid observes, if we notice that we do not understand how it is that we manage to connect our minds to objects in the world, then it cannot help to say that we do this by first connecting our minds to mental representations unless we understand how it is that we manage to connect our minds to those mental representations. This consideration gives the following question its force: Why is the perception of a mental intermediary like an idea supposed to be more intelligible than the direct perception of a physical object? If it is no more intelligible, then the representational theory is not serving to explain what it was intended to explain. (See EIP 2.14, 185.)

In addition to burden of proof arguments against the Way of Ideas and the representational theory of perception, Reid also deploys a number of detailed arguments against specific components of these theories and against commitments they presuppose to be true. Though these arguments are unsuitable for recapitulation in the format of an encyclopedia entry, we report one such argument in brief in an effort to offer a hint at the robust detail, nuanced reasoning, and attention to physiological facts in Reid's theory of perception.

In one of a small handful of arguments that David Hume explicitly offers for a representational theory of perception, he concludes that “nothing can ever be present to the mind but an image or perception” (Enquiry 12.9; see Treatise, 187) by reasoning from considerations having to do with what is known as ‘perceptual relativity’. Hume writes, “The table, which we see, seems to diminish, as we remove farther from it: but the real table, which exists independent of us, suffers no alteration: it was, therefore, nothing but its image, which was present to the mind. These are the obvious dictates of reason” (Enquiry 12.9). This is perhaps the most compelling argument for the representational theory of perception.

Reid responds to this argument with several objections. First, Reid's analysis of each of the senses in Inquiry convince him that some senses do not represent physical objects in the same way that all the others do. Touch (IHM ch. 6), for example, presents qualities of objects to the mind in ways more direct than does vision (IHM ch. 7), resulting in what has been referred to as Reid's hybrid theory of perception. A conclusion generalized to all the senses (“nothing can ever be present...”) but based solely on one sense is therefore invalid.

The next of Reid's objections is more involved, requiring introduction of a key distinction Reid makes on the basis of his attention to the phenomenology of visual experience. First, though, notice Hume's use of the term ‘table’ and ‘the real table’ in the argument above. Following Berkeley's New Theory of Vision, Reid distinguishes between visible figure from tangible figure (IHM 6.2, 81–2), or later, which is virtually the same distinction, between ‘apparent magnitude’ and ‘real magnitude’ (EIP 2.14, 181). The tangible or real figure of an object is measured by yards or inches, but the visible figure is not. Instead, the visible figure depends for its geometric properties—the surface area that the table occupies in the visual field—upon properties of the tangible figure, including its shape and its distance from the eyes. Reid recognizes the obvious phenomenon of perceptual relativity, for example, that when I see a table at 10 yards and at 100, its “visible appearance, in its length, breadth, and all its linear proportions, is ten times less in the last case than it is in the first” (IHM 6.2, 81–2). The tangible figure is measured by different means, sensed by a different faculty, and is extended in three dimensions. This leads Reid to argue that “The ingenious author has imposed upon himself by confounding real magnitude with apparent magnitude,” that is, Hume equivocates (EIP 2.14, 182).

A pressing question arises at this juncture: Hasn't Reid now adopted a position according to which there are perceptual intermediaries in the visual perception process? If so, doesn't this imply that Reid's theory will share many of the foibles with which he charges the Way of Ideas? Most answers to these two questions have proven to be contentious in part because Reid's interpreters often bring to this issue prefabricated, a priori definitions of ‘intermediary’, ‘representation’ and ‘directness’. While Reid's theory of visual perception implies that visible figures are seen, visible figures are radically unlike ideas. Visible figure is not merely a representational intermediary; it is a relational property between physical objects and eyes of perceivers. Only because ideas lack these characteristics is Hume able to reason from the claim that mind-independent tables are not immediate objects of awareness to his stated conclusion above that we immediately perceive only ideas or representations. That is the first of two important points in response to the first question.

The second enters into Reid's development of a consistent geometry for visible space, perhaps the most technically brilliant piece of writing by any major British empiricist. This work allows Reid a crucial reply to advocates of representational theories. Reid discovered and mathematically described a law-like variation in the visible figure of an external object with intrinsic (shape, size) and extrinsic (distance, angle of orientation) properties of the tangible figure. Reid summarizes his conclusion writing:

[T]he real table may be placed successively at a thousand different distances, and, in every distance, in a thousand different positions; and it can be determined demonstratively by the rules of geometry and perspective, what must be its apparent magnitude and apparent figure, in each of those distances and positions.” (EIP 2.14, 183)

Hume assumes that the relationship between a visible figure and a tangible figure is subjective and mind-dependent. Not only is that erroneous, but, given Reid's work, the systematic variation of the visible figure with the tangible figure is in fact evidence for the objectivity of its independence from one's mind.

Reid further argues that this objective relationship between, for example, seeing the visible figure of a coin and conceiving of the coin becomes automated over time through repeated experience. Perhaps the first time I saw a coin it was presented to me at an angle, its visible figure an ellipse. I might mistakenly form a perceptual belief about an elliptical object, even though the coin is circular. Over time, this process is habituated through a process that Reid describes with the help of a distinction between original and acquired perceptions. In short, my faculty of visual perception, if given experience, will successfully model the geometrically demonstrable relationship between visible figure and tangible figure.

This family of arguments has received considerable attention due to a number of its complexities. These involve attempts to answer questions including the following: As we have seen, through his science of perspectival shapes of objects Reid argues that they are geometrically equivalent to shapes projected onto surfaces of spheres. What is Reid's formal proof for this, and is it valid (Yaffe 2002)? Does Reid offer the first recorded non-Euclidean geometry in the history of mathematics (Daniels 1972)? What is the bearing of Reid's repeated attempts to derive Euclid's parallel postulate from the axioms of incidence on an interpretation of the geometry of visible space as non-Euclidean (Grandi 2005)? Where does Reid's theory of perception and geometry of visibles leave the ontology of visible figure (Nichols 2007, ch. 4)? In what ways is visible figure the object of visual perception, and in what ways not (Yaffe 2003; Falkenstein and Grandi 2003)? Does Reid's geometry of visible space jeopardize his theory's ability to avoid a representational theory of visual perception (Van Cleve 2002)? Does visible figure and awareness of it preclude non-inferential perceptual knowledge from vision, or rather, what is the relationship between original and acquired perceptions and visible figure (Nichols 2007, ch. 8)?

Now that we know how and why Reid argues against the Way of Ideas' representational theory of perception, we needn't address these questions in order to continue with a discussion of the components of Reid's own more direct theory of perception. Here we need to keep in mind the fact that, though contemporary philosophers write a priori about perception, sensation, and knowledge, Reid does not offer necessary and sufficient conditions for perception or for its component processes. Consistent with his Newtonian empiricism, Reid is aiming for something else altogether: observations and accurate experiments that reduce to general rules (EIP 1.3, 49–50; EIP 2.8, 120–1). Though operations of our intellectual powers are not definable or analyzable a priori, it is possible to describe the operations Reid has in mind.

According to Reid, the perceptual process operates as follows. Individuals with functioning sensory organs and a developed brain interact with physical objects in the world. These objects cause sensory experiences in individuals. These sensations function as natural signs for qualities of the objects. The experience of a sensation orients my cognition so as to form a conception of a quality of a mind-independent object. Sometimes, though rarely, an individual's perception of an object will not only cause a sensation but will also cause the person to become aware of the sensation—perhaps even at the exclusion of any further awareness of primary qualities of the object. For example, when I get hit by a baseball thrown 90 mph I focus on my pain sensations, not the qualities of the ball. To perceive an object is to be aware of the object or its quality in a particular way, as the possessor of a particular quality, and, at the same time, to be convinced that the object exists and is as it is conceived it to be. To defend a common sensical theory of perception that is supported by observation and experiment, and that is capable of delivering knowledge of real objects, Reid thinks he needs to show that we are directly aware of real objects, in contrast to key features of the Way of Ideas' representational theory of perception just discussed. While there is debate over the precise sense in which, for Reid, we are directly aware of objects, this much seems clear: whatever the sense of “direct” is in which the subscribers to the representational theory take us to be directly aware of ideas, it is in that sense that Reid takes us to be directly aware of real objects.

3.3 Sensations as Natural Signs of Qualities

In addition to being a Newtonian empiricist, Reid is an expert phenomenologist, acutely aware to finely grained features of our experience, especially our sensory experience. When we touch a table, while we conceive of it and often form beliefs about it, we also sense it. (See 2.1 Conceiving) The immediate effect that objects have on us is to cause sensations. Sensations are always associated with a particular organ of sense; they are always distinctly of, for instance, touch or vision. Sensations are the feelings that are the immediate mental causal consequences of the influence of objects on us. We become aware of the qualities of objects following the sensations that those objects cause. However, for Reid, the conceptions of objects that follow from our sensations are not derived from our sensations since they do not bear any kind of resemblance to the qualities which cause them. Awareness of sensations are not, for Reid, essential intermediaries for formation of perceptual beliefs. So what is the precise relationship between sensory experiences and conceptual content? This is a delicate question for Reid since the directness of his theory of perception depends upon advocacy of a physiologically and phenomenally real theory that accounts for our experience while avoiding theoretical pitfalls that risk dragging his theory much closer to a representational theory than Reid would like.

As we have often in this entry, we begin with historical context since Reid's theory of the relation between sensations and qualities will appear stranger than it is without background. According to the Way of Ideas, ideas and images are mental representations in an individual's mind, and my perceptual awareness of a table depends upon my prior awareness of these ideas of sensation. This veil of perception is why advocates of the Way of Ideas struggled to provide epistemic justification for beliefs about external, mind-independent, qualities of physical objects, and avoid skepticism. But besides the epistemic problem, advocates of ideas faced a difficulty accounting for the origins of the contents of our very ideas of external objects. Though not easy to appreciate, this problem it is quite important.

Reid argues that advocates of the Way of Ideas do not have a plausible solution to this problem. Hume says bluntly that “[E]very simple idea has a simple impression, which resembles it” (Treatise, 3), which is a statement of what is known as the Copy Principle: ideas have the content that they do because they are copies, and resemblances, of impressions. Think of a table. For Hume, your thought of a table is derivative and copied from a sensory impression that you have had of that very table. The explanation of the content of the idea of that table thus concerns the contents of your simple impression of the corresponding physical table. The Copy Principle is an exceedingly powerful tool on behalf of the Way of Ideas for a variety of reasons, but Reid is unimpressed with the evidence on its behalf, especially as presented by Hume in Treatise. Reid's response to Hume leads to an argument, which we can call his ‘Sensory Deprivation Argument’.

Reid's Sensory Deprivation Argument proceeds as follows. First, Hume's stated justification for the Copy Principle is inductive: he challenges people to find an idea that is not derived from a sensory impression, after he says that it appears all his ideas are copied from sensory impressions. But that, says Reid, is an exceedingly weak justification (EAP 1.4, 23). Besides, Hume's claim that the principle is “certain” is mistaken because the argument he sets out for the principle is inductive (IHM 5.7, 69–70, 75–6). After those ground clearing moves, Reid begins the argument proper with a thought experiment. Exhibiting affinities with Condillac's remarkable Treatise on Sensations (1754), Reid asks his readers to imagine a blind adult subject. Not only has he lost his sight, but he has “lost all the experience, and habits, and notions he had got by touch; [he lacks] the least conception of the existence, figure, dimensions, or extension, either of his own body, or of any other; but to have all his knowledge of external things to acquire anew, by means of sensation, and the power of reason, which we suppose to remain entire” (IHM 5.6, 65). Reid imagines introducing this blind experimental subject to a number of tactile sensations, one by one, from the most simple to the most involved: a single pin prick in a split second of time; a blunt object pushed against a small surface area of skin; the same object pushed against skin over a period of time “with a force gradually increased till it bruises him”; an object covering a large surface area of skin, applied over a period of time, and so on. Reid's emphasis on tactile sensations is important to understand: he uses this running example because ideas of primary qualities are the most important for gaining knowledge of the world and are the ideas essential for any science.

Once a handful of skin cells are stimulated for the briefest of moments by a pin, the subject has received a sensory impression—or in Reid's language, he has had a sensation—but, Reid argues, this does not equip the individual to formulate an idea of extension or figure, space or motion, all primary qualities of the pin. He writes, “[The primary qualities] have no resemblance to any sensation, or to any operation of our minds; and, therefore, they cannot be ideas either of sensation or of reflection” (IHM 5.6, 67). For each subsequent iteration of tactile sensations, Reid argues that those sensations too are incapable of delivering to the subject ideas of extension, figure, space or motion. His conclusion has two parts. First, the Way of Ideas's story about the relation between sensations and the intentional contents of conceptions is mistaken. Second, with an eye toward developing his own theory of sensations, he writes,

[T]his connection between our sensations and the conception and belief of external existences cannot be produced by habit, experience, education, or any principle of human nature that hath been admitted by philosophers. At the same time, it is a fact that such sensations are invariably connected with the conception and belief of external existences. Hence, by all rules of just reasoning, we must conclude, that this connection is the effect of our constitution, and ought to be considered as an original principle of human nature, till we find some more general principle into which it may be resolved. (IHM 5.3, 61/122b)

The process by which sensations give rise to our conceptions of objects is something Reid calls ‘suggestion’. Sensations in this process he calls ‘signs’. The qualities of objects are ‘suggested’ by our sensations when they function as signs, so when we have sensations we come to be aware of those objects as possessing those qualities. But what is suggestion supposed to be? The first thing to notice is that the suggestion relation or the ‘sign-signified’ relation is contingent. Whereas philosophers prefer necessities, Reid does not believe the messiness of the actual perceptual process contains any necessity at this juncture. Second, suggestion is a pseudo-linguistic notion for Reid. Signs suggest conceptions of that which they signify. The word “dogs”, for instance, leads those who are familiar with the word to think of certain domesticated animals who are also man's best friends.

But for those who already know the term, this does not happen by hearing the word “dogs” then deriving or inferring some object that has some peculiar fitness to the word. The relation of signs to things they signify in spoken and written language is almost always arbitrary in the sense that there is no similarity between dogs and the word “dogs”. In this sense, “dogs” is an artificial or artifactual sign, for Reid, in contrast to natural signs. Blushing signifies one of a small number of mental states because blushing is caused by events of embarrassment, anger, or romantic stimulation. Blood rushing through the subcutaneous circulatory system in the face reliably occurs, across members of our species, in response to a small set of stimuli with apparent universality, making blushing a natural sign. We discover this relationship by observation and experience.

However, according to Reid, a subset of natural signs lead us to think of what they signify without any prior experience. Members of this category “which, though we never before had any notion or conception of the things signified, do suggest it, or conjure it up, as it were, by a natural kind of magic, and at once give us a conception, and create a belief of it” (IHM 5.3, 60). Put your hand on a table, pause and experience the sensation of hardness. This tactile sensation leads us immediately to conceive of that which caused it as being hard, as having a certain resistive construction. But we are aware of the table's hardness, which caused the sensation, automatically. We do not understand why it is that we think of this special kind of physical constitution after having this kind of tactile sensation. Nonetheless, we must “conclude, that this connection is the effect of our constitution, and ought to be considered as an original principle of human nature” (IHM 5.3, 61). This is the defining feature of the kind of natural signs of which the tactile sensation of hardness is an instance: these signs lead us to conceive of what they signify simply because we are built in such a way as to have such conceptions on encountering such signs. Reid's approach to this relationship contrasts sharply with that taken by most advocates of the Way of Ideas, who attempted to posit a strong relationship between ideas of sensation and qualities of physical objects.

Placing my hand on a table, my tactile sensation immediately leads my mind to a conception or apprehension that I am touching a hard object. When does one's conception of an object as having a particular quality amount to a perception, a conception accompanied by a conviction of its accuracy? The answer is: when one comes to have that conception because one has encountered a natural sign which leads one to the conception, and that natural sign leads one to the conception merely because of one's constitution. Conviction in the accuracy of a conception is bestowed on the conception, Reid thinks, just when the relevant conception comes about because of our nature or constitution. When we conceive of an object in a particular way merely because it is in our nature to conceive of the object that way, then the conception is non-optional, unavoidable, and is thus one that we cannot help but trust. Perceptions, then, are dictates of common sense: to be aware of an object in perception is to have a belief which you cannot give up given your constitution.

Reid believes that our minds come to be connected to the mind-independent world in something like the way that we come to grasp objects through a language designed for the purpose. However, when we come to be aware of objects through our senses, we do so by utilizing something like a language embedded in our constitutions: our sensations function like a language that nature has constructed. While it is in a sense only a metaphor to say that we know about the world because the world speaks to us, it is a metaphor that illuminates the facts as Reid sees them.

3.4 Primary and Secondary Qualities

Intertwined with Reid's arguments that we can be immediately aware of objects through their relational properties—such as their apparent magnitudes—are Reid's arguments regarding the distinction between primary and secondary qualities. As we would expect, Reid approaches this distinction as a scientist of the mind rather than as a metaphysician, and, as we would also expect, Reid's entrance into this terrain is paved with references to earlier thinkers.

Locke thought that our ideas of “primary qualities”—shapes, sizes, motions, textures and physical construction—resemble the qualities which cause them. However, according to Locke, our ideas of a variety of other qualities—colors, sounds, tastes and smells—do not. Ideas of colors, sounds, tastes and smells, or “secondary qualities,” are caused by certain complex configurations of primary qualities that bear no resemblance to the ideas which they cause. Reid is deeply struck by Berkeley's attack on this distinction at Principles of Human Knowledge 1.9–15. He agrees with Berkeley that no mental state or object could possibly resemble anything that is not, itself, a mental state or object. In Berkeley's famous words, “An idea can be like nothing but an idea” (Principles of Human Knowledge 1.8). Mental states and objects have only mental properties, but only something that is, itself, a mental state or object can have a mental property. Hence, nothing can resemble—that is, share a property in common with—a mental state or object other than another mental state or object. Berkeley took this point to show that no non-mental cause of an idea could resemble it, whether the relevant idea were an idea of a shape or a color. Berkeley concludes that Locke's distinction between primary and secondary qualities is a grand mistake.

Reid accepts, for roughly Berkeley's reasons, that sensations cannot possibly resemble their causes—a fact that Reid deploys in his Sensory Deprivation Argument discussed above. Further, he accepts Berkeley's objections to Locke, and takes them to show that no mental events or states, whether sensations or the conceptions of objects that follow them, could possibly resemble any non-mental object. Another reason that Reid cannot draw the distinction between primary and secondary qualities in the way that Locke did is that he denies that conceptions of objects which we have following sensory experiences are to be analyzed as perceptions of ideas. Instead, these conceptions function to make us aware of qualities in objects that caused the sensations. All of this would make it seem that Reid would simply side with Berkeley and deny that there is any important difference between primary qualities and qualities like colors, sounds, tastes and smells. Instead, Reid defends the distinction between primary and secondary qualities on grounds quite different from Locke's, grounds that he takes to be immune to Berkeley's criticisms of the distinction.

Reid accepts that the qualities which we ordinarily conceive objects to have—whether shapes, sizes and motions, on the one hand, or colors, sounds, tastes and smells, on the other—are genuinely possessed by those objects (barring illusions and disorders of various sorts, which are, incidentally, difficult for any direct theory of perception like Reid's to explain). He thinks that shapes, sizes and motions are intrinsic properties of objects while colors, sounds, tastes and smells are relational properties of objects. But neither secondary nor primary qualities resemble the sensory experiences that they immediately cause in us. Colors, sounds, tastes and smells are powers to produce certain characteristic sensations in us in normal conditions. To believe that a rose has an agreeable smell or a red color is not to perceive any intrinsic qualities of the object, but is, rather, to perceive that the object bears a certain relation to something else—our minds. Reid writes,

The object of my perception, in this case, is that quality in the rose which I discern by the sense of smell. Observing that the agreeable sensation is raised when the rose is near, and ceases when it is removed, I am led, by my nature, to conclude some quality to be in the rose, which is the cause of this sensation. This quality in the rose is the object perceived; and that act of my mind by which I have the conviction and belief of this quality, is what in this case I call perception. (EIP 2.16, 194)

Physical structures of the rose in front of me—the anther in the rose's stamen—produce pollen, which has a certain molecular composition that results in my sensation of its odor. Other molecules in the petals of the rose reflect light at a certain wavelength which in turn causes in me a certain characteristic visual sensation of red. If I am speaking correctly when I say “That rose smells good”, I am reporting the fact that I conceive of the rose as possessing a particular relational property: I am aware that the rose has the property of being-such-as-to-cause-in-me-sensations-of-a-sweet-smelling-odor. Ultimately, the rose possesses this relational property because of facts about its molecular structure that account for its producing this odor in a certain way, and facts about me that account for the fact that these pollen molecules enter my nasal cavity, eventually reaching the olfactory bulb, and cause certain sensations in my mind. But when I am aware of the odor of the rose, I am aware of none of that; I am aware only of the fact that there is something about the rose that makes it cause in me certain sensations in normal conditions.

Our conceptions of qualities such as smells and colors are to be contrasted with our conceptions of primary qualities or configurations of primary qualities, such as hardness. Say I'm holding the rose's stem in my hand while I'm looking at it. I am having two importantly different sensations: a visual sensation of red, and a tactile sensation of hardness. For Reid, neither sensation resembles anything in the object; both give rise to conceptions of the object as possessing certain properties. The visual sensation gives rise to a conception of the object as possessing a particular relational property: its power to produce certain sensations in me in normal conditions. The tactile sensation gives rise to a conception of the rose's stem as possessing a particular intrinsic property: the complex configuration of primary qualities that is hardness.

For both Locke and Reid, we are aware of objects as they are intrinsically only when our awareness is caused by the primary qualities of objects. But for Reid, and not for Locke, we are genuinely aware of objects as they are when our awareness results from the secondary qualities of objects; but we are aware of those objects only as they are relative to us, and not as they are in themselves.

“When a primary quality is perceived, the sensation immediately leads our thought to the quality signified by it, and is itself forgot.” (EIP 2.17, 204)

“[T]here appears to be a real foundation for the distinction; and it is this—that our senses give us a direct and a distinct notion of the primary qualities, and inform us what they are in themselves. But of the secondary qualities, our senses give us only a relative and obscure notion. They inform us only, that they are qualities that affect us in a certain manner—that is, produce in us a certain sensation; but as to what they are in themselves, our senses leave us in the dark.” (EIP 2.17, 201)

“[T]he sensations belonging to secondary qualities are an object of our attention, while those which belong to the primary are not.” (EIP 2.17, 204)

Secondary and primary qualities are characterized by their relations to the mind perceiving them and to the physical qualities in objects that they signify. Primary qualities stand out as qualities of which we have “direct” and “distinct” notions. This is not so for secondary qualities. To return to Reid's rose, he writes of the smell of the rose that

I have a distinct notion of the sensation which it produces in my mind. ... The quality in the rose is something which occasions the sensation in me; but what that something is, I know not. My senses give me no information upon this point. The only notion, therefore, my senses give is this—that smell in the rose is an unknown quality or modification, which is the cause or occasion of a sensation which I know well. The relation which this unknown quality bears to the sensation with which nature hath connected it, is all I learn from the sense of smelling; but this is evidently a relative notion. The same reasoning will apply to every secondary quality. (EIP 2.17, 202/314b)

Reid does defend a primary/secondary quality distinction, but, unusually, Reid's distinction is drawn not in metaphysical terms but in epistemic terms premised upon discussion of the differing ways that secondary and primary qualities relate to our minds (Nichols 2007, ch. 6).

An important note at this juncture is that Reid very infrequently uses contemporary epistemological terms such as “knowledge”, “rational”, or “justified”, and even when he does, he does not offer necessary and sufficient conditions for their definition. Reid says above that sensations caused by primary qualities “inform us” of the qualities in the objects that caused them. One ought not look to Reid's epistemology for a detailed formal apparatus clearly identifying his externalism about justification, for example, even though he can be credited with bringing what we now call externalism about justification into Early Modern philosophy.

3.5 Responding to Skepticism about the External World

We are now in a position to understand the force of Reid's most important response to any argument purporting to show that the external world either might not exist, or might not be anything like the way we take it to be. In one canonical statement of his position, Reid says,

The sceptic asks me, Why do you believe the existence of the external object which you perceive? This belief, sir, is none of my manufacture; it came from the mint of Nature; it bears her image and superscription; and, if it is not right, the fault is not mine: I even took it upon trust, and without suspicion. Reason, says the sceptic, is the only judge of truth, and you ought to throw off every opinion and every belief that is not grounded on reason. Why, sir, should I believe the faculty of reason more than that of perception?—they came both out of the same shop, and were made by the same artist; and if he puts one piece of false ware into my hands, what should hinder him from putting another? (IHM 6.20, 168–169)

The mistake that the skeptic makes, according to Reid, is to deny the truth of something that is demanded by our constitutions. To perceive an object as possessing a particular property is to have a conception of the object delivered by one's constitution. What makes us convinced of the accuracy of the conceptions of objects involved in perception is that they arise from our constitutions. But, asks Reid here, why do we find skeptical arguments so compelling? Why would someone sincerely accept the radical skeptical conclusions following from Descartes's hypothesis of the evil demon?

Ultimately, we think that such arguments lead to their conclusions because we accept certain logical principles—such as the law of non-contradiction, or modus ponens—which appear to us to be self-evident. But to say that such principles are self-evident is just to say that we cannot help but accept them. It is not to offer any non-circular justification of those principles. But the irresistibility of a belief is a very good indicator, Reid thinks, that we hold that belief merely because of the way we are built, merely because of our constitution. But then the skeptic has merely placed the skeptical conclusion on the same footing as the common sense belief about the external world: both rest on something that we are compelled to believe by our constitutions. However, in order to overthrow common sense, the skeptic must place the skeptical conclusion, rather, on a firmer footing than the common sense conclusion. Thus, the skeptic gives us no reason to reject common sense beliefs about the external world. Reid has defended common sense through construction of a direct theory of perception that avoids the pitfalls of the Way of Ideas' representational theory. Rather than landing in the “coal pit” of skepticism, as Reid calls it, his theory purports to deliver knowledge of the external world.

4. Causation and Free Will

4.1 Objecting to Hume

Reid develops his account of causation in light of Hume's account. As Reid sees it, Hume starts with the assumption that if we are to learn what causation is, we must first determine from what aspect of our sensory experience the concept of causation is derived. Hume would put the point in terms of the Way of Ideas as follows: we must determine from what impression our idea of causation is copied. However, Hume believed he had discovered that there is nothing in our sensory experience corresponding to our ordinary notion of the causal relation. In an inversion of the empiricist method attributed to Reid above, Hume believed that causes necessitate their effects, then he followed this commitment by arguing that we lack sensory awareness of this necessitation. We see the first billiard ball hit the second. We see the second move. We do not see the movement of the first assure, or necessitate, the movement of the second. So Hume concludes that causation must be something different from what we take it to be ordinarily.

But what is it? To answer this question, we must determine from what sensory experiences we derive the idea of causation. It turns out, as Reid reads Hume, that the sensory experiences that give rise to our idea of causation are sensory experiences of what Hume calls constant conjunction. The heating of the water is regularly followed by the water's boiling. To say that the one event causes the other is just to say that the two events always co-occur, or that there is a brute law linking them. This is not to say that the first event necessitates the second. The necessitation that we ordinarily take to be involved in causation is not in the world; it is in our heads as an expectation arising due to previous experience.

Reid accepts much of the negative side of Hume's view of causation while rejecting Hume's assertions of the import of those negative discoveries. Reid agrees, that is, that we have no sensory experience of the necessitation of an effect by its cause. But this does not imply our ordinary concept of causation is mistaken. Instead, Reid thinks, the concept of causation is not an idea copied from a sensory impression in the first place. Reid's complex thoughts here are tied to perception and the role of sensations in perception. (See 3.2 Reid's Arguments Against Representationalism, above.) For him, sensations never bear resemblance to the qualities they help us to perceive. It is hardly a surprise, then, that the sensory experiences from which our thoughts about causation spring bear no resemblance to the causal relation. But this fact no more undermines our concept of causation than the lack of resemblance between our sensory experiences of ordinary physical objects and those objects themselves undermines our thoughts about such objects. Like our thoughts about objects, our thoughts about the causal relation are genuinely about the causal relation, despite the fact that the sensations from which those thoughts spring, i.e.the sensations of the relation of constant conjunction, bear no resemblance to the relation they lead us to think about. We have no sensations resembling necessitation, and, yet, causes necessitate their effects.

However, Reid also offers criticisms of Hume's view of causation that can be accepted independently of the Reidian view of perception and sensation. Two of his most influential criticisms are of Hume's view that our ordinary concept of causation is reducible to the relation of constant conjunction.

Of the first he writes, “[I]t would follow from [Hume's definition of causation], that whatever was singular in its nature, or the first thing of its kind, could have no cause” (EAP 4.9, 250). Reid's point is that if the relation of causation is really that of constant conjunction, then the first time that two types of event are conjoined, the first cannot be the cause of the second. If there is no history of conjunction, there is no causation. It would seem to follow from Hume's definition, for instance, that if an earthquake razes Mexico City, and no earthquake has ever done so before, then the earthquake is not, in fact, the cause of the city's fall, an absurd implication. This objection might not show Hume's theory is mistaken—we omit consideration of it further here—but it does pose a question with which any Humean must wrestle: Which constant conjunctions are the genuine ones on the basis of which the causal relation can be said to hold, and which are not? The more specifically any two events are described, the more likely that there will be no history of conjunction of the relevant sorts of events. But what degree of specificity or generality in description is the right degree?

The problem is made clearer by Reid's second objection to Hume's analysis of causation and constant conjunction. He writes, “It follows from [Hume's] definition of a cause, that night is the cause of day, and day the cause of night. For no two things have more constantly followed each other since the beginning of the world” (EAP 4.9, 249). Since we don't ordinarily think that day is the cause of night, or vice versa, Hume must deny that the two are actually constantly conjoined, or, rather, he must insist that the constant conjunction between the two of them is not of the right sort for the relation between them to be one of causation. Hume thinks that there is causation between two events just in case there is a law linking them and also thinks that there is a law linking two events just in case they are constantly conjoined. Reid's first objection shows that it is not the case that wherever there is no constant conjunction there is no law. His second objection shows that it is not the case that wherever there is constant conjunction there is a law. Constant conjunction is neither necessary nor sufficient for the presence of a genuine law. The hard problem that remains for the Humean, then, is to produce criteria for distinguishing genuine laws from regularities that are not laws at all.

These criticisms lead Reid to hold that there is a legitimate causal relation between two events whenever the two are conjoined by a law of nature, even if laws of nature do not simply amount to constant conjunctions. He uses the term physical causation to refer to the relation that holds between two events just in case they are conjoined by natural law. He takes the discovery of the physical causes of phenomena to be central both to the sciences and to ordinary life (see IHM 6.12, 122; EAP 1.5, 28–9; EAP 4.3, 211–2). But he also holds that genuine causation, what he calls efficient causation, is not reducible to physical causation. The reason is that, for him, a law of nature is not a brute conjunction between events. Rather, it is a regularity in the behavior of the efficient cause of observed phenomena. Consistent with remarks above (see 1.2 Newtonianism and Empiricism), Reid writes,

[S]upposing that all the phenomena that fall within the reach of our senses, were accounted for from the general laws of nature, justly deduced from experience; that is, supposing natural philosophy brought to its utmost perfection, it does not discover the efficient cause of any one phenomenon in nature. The laws of nature are the rules according to which the effects are produced; but there must be a cause which operates according to these rules. The rules of navigation never navigated a ship. The rules of architecture never built a house. (EAP 1.6, 38)

It is a law that unsupported objects close to the earth will fall. What this means, Reid thinks, is that the physical cause of the fall of an object regularly causes objects to fall when they are unsupported. Physical causation, for him, is parasitic upon the more basic kind of causation, namely efficient causation. But what is efficient causation? Reid writes, “In the strict and proper sense, I take an efficient cause to be a being who had power to produce the effect, and exerted that power for that purpose” (Letter to James Gregory, in Correspondence 174). Efficient causation is necessitation of the sort that Hume thought not to exist. To efficiently cause an event is to be capable of seeing to it that the event occurs, and to make an effort to see to it that it does. Thus, at the bottom of Reid's theory of causation are his notions of power and exertion.

4.2 Power, Exertion and Moral Liberty

Reid is clear that power is not the sort of thing that admits of a logical definition. We cannot reduce it to some set of simpler qualities. However, this doesn't mean that we can't say anything about what power is. On the contrary, Reid makes a variety of claims about power. Importantly, he claims that power is the quality that, when coupled with exertion, necessitates a particular effect. Taking a cue from ordinary language, he holds that it is a contradiction to say that an entity has the power to do something, and exerts that power, and yet the effect fails to come about. If the effect fails to come about when the entity exerts itself, we might say, what that shows is that the entity only seemed, but didn't actually, have the power to bring about the effect. Reid also claims that any agent who has the power to do something also has three other inter-related powers: the power not to do the thing, the power to try to do that thing (that is, the power to exert his power to do the thing), and the power not to try to do that thing. He claims further that any agent who has the power to do something must believe himself to have that power.

Any one of these claims can be questioned, even if Reid is right that they are embedded in our ordinary concept of power. Take, for instance, the claim that an agent who has the power to do something also has the power not to do it. Locke offers the following example, which seems to be a counterexample to this claim:

[S]uppose a Man be carried, whilst fast asleep, into a Room, where is a Person he longs to see and speak with; and be there locked fast in, beyond his Power to get out: he awakes, and is glad to find himself in so desirable Company, which he stays willingly in, i.e.

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