[In the following essay, Cummins examines Berkeley's belief about perception, claiming that he limits himself because he refuses to separate the physical world from the perceptions of the senses.]

In Section One of the Principles,¹ Berkeley divides the objects of human knowledge into three groups. They are either “ideas actually imprinted on the senses, or else such as are perceived by attending to the passions and operations of the mind, or lastly ideas formed by the help of memory and imagination, either compounding, dividing or barely representing those originally perceived in the aforesaid ways.” Berkeley proceeds to specify, with respect to ideas of the first division, the qualities which are the proper objects of each of the five senses. By smell, for example, odours are perceived and by hearing, sounds. Next he states, “And as several of these are observed to accompany each other, they come to be marked by one name, and so to be reputed as one thing.” After listing some of the things constituted by ideas of sense, for example, apples, stones, and books, he asserts that as they are pleasing or disagreeable, such collections excite “the passions of love, hatred, joy, grief and so forth.” In the next section, ideas are contrasted to that which “knows or perceives them and exercises divers operations, as willing, imagining, remembering, about them.” That which knows is not an idea. No, Berkeley insists, it is “a thing entirely distinct from them, wherein they exist, or, which is the same thing, whereby they are perceived.” As if to explain, he adds, “for the existence of an idea consists in being perceived.” The meaning and import of this startling claim are made clearer at the beginning of Section Three, for there Berkeley asserts

That neither our thoughts, nor passions, nor ideas formed by the imagination, exist without the mind, is what every body will allow. And it seems no less evident that the various sensations or ideas imprinted on the sense, however blended or combined together (that is, whatever objects they compose) cannot exist otherwise than in a mind perceiving them.

No sound, no odour, in short, no sensed quality can exist unperceived. Neither can any combination of sensed qualities, not even that immense and elaborate combination to which the word mountain is applied. The reason? Because, in Berkeley's phrase, “Their esse is percipi.”

Berkeley's immaterialism is rich and diverse. He developed an agency theory of causation and used it to argue for God's existence. He insisted and tried to establish that mathematics and the natural sciences can and must be metaphysically neutral. He attempted to secure genuine perceptual knowledge in the absence of material substances and genuine perceptual knowledge of minds in the absence of ideas of them. He offered a proof of the immateriality of the soul. For all that, however, the core of his system is the attack on material substance. To suppose the existence of material substances (unperceiving things capable of existing unperceived) is to open the door to scepticism and to do so needlessly, he argued, since the supposition itself is either meaningless or contradictory. In attempting to prove these central positions, Berkeley reiterated and reiterated his contention that no sensible object can exist unperceived, that their esse is percipi.

Sections 1 through 17 constitute a systematic demonstration of the non-existence of material substance. After introducing sensibles and other objects of awareness, contrasting them with minds, and insisting that no sensible object can exist unperceived, Berkeley asserts in Section 7 that minds (active perceiving things) are the only substances. He has already shown that no sensible object (combination of sensible qualities) is a material substance, since to be a material substance is to be capable of existing unperceived, whereas no sensible qualities or combination of such can so exist. Their esse is percipi. In Section 7, he adds that no sensible quality can exist in a material substance, since the latter do not perceive. In Section 8, Berkeley rejects the alternative that sensible objects are images and material substances archetypes. The alternative presupposes that something imperceptible can have the same types of qualities as a sensible object, which is absurd. Berkeley rejects, too, the theory of primary qualities. Extension, shape, and other known qualities offered as examples of primary qualities are sensible qualities. They are either sensed or defined in terms of sensed qualities. Like sounds, colours, and odours, therefore, they must be perceived to exist. Hence they cannot be real properties of material substances. Nor can it be said that material substances underlie or support sensible qualities (Section 16). If ‘underlie’ and ‘support’ are not empty metaphors, they imply that material substances are extended. Since extension is a sensible quality, this position generates either instant absurdity or an infinite regress. To give content to the doctrine of material substance leads to inconsistency, but to refuse to give it content leaves only an insignificant phrase. Berkeley utilized basically the same dilemma in the Three Dialogues to attack the claim that material substances cause sensible objects. If one is not using “material substance” for what accurate thinkers call minds, those being genuine causes, one must specify what one means by “cause” and how material substances operate causally. But virtually all descriptions are framed with reference to sensible qualities. Because no sensible quality can exist unperceived, then, the defender of material substance is reduced to insignificance or absurdity. Once it is established that sensed qualities cannot exist unperceived, the doctrine of material substances cannot be saved from incoherence.

What exactly is expressed by and what is the force of “Esse est percipi”? What is the basis for the claim that no ideas of sense or combination of them can exist unperceived? There have been a multitude of conflicting answers to these questions, none of them definitive. It is convenient, at the very least, to divide them into two groups. There are, first, those which found Berkeley's rejection of unsensed sense objects on an explicit or implicit position concerning the nature of the immediate objects of sense or the structure of the process of perceiving. These can be styled metaphysical interpretations. To argue, for example, that the dependence of sensory objects on perceivers is a consequence of interpreting perceiving in terms of the inherence relation between accident and substance is to offer a metaphysical interpretation.² Second, there are those answers which emphasize the nature and limits of conceptualization, meaning, or the criteria and limits of knowledge. They may be termed epistemological interpretations. To maintain, for example, that Berkeley's denial of abstract ideas led him to define “existence” in terms of being perceived, an actual characteristic of objects which are known to exist, is to develop an epistemological interpretation.³

Thomas Reid developed a historically oriented critique of the doctrine of sensory images in his Essays on the Intellectual Powers of Man. At one stage, he fashioned an interpretation—a metaphysical interpretation—of Berkeleyan ideas of sense. It is both ingenious and plausible. Reid's interpretation provided him an object for criticism, but should not for that reason be rejected. In Reid's portrait, Berkeleyan idealism is a powerful, tightly-reasoned system which reveals several critical turning points in philosophy.

According to Reid, Berkeley's system is based on the sweeping but false thesis that sensations are the only objects of perception, that is, that what one perceives whenever one perceives is invariably a sensation or combination of sensations.⁴ Reid assigned a quite definite meaning to the term “sensation”; in his philosophy it designates a class of entities which are important elements in, though not objects of, acts of perceiving. In order to assess Reid's interpretation, the following procedure may prove effective. First, what Reid meant by ‘sensation’ shall be specified and clarified. Second, textual and historical evidence for Reid's interpretation of Berkeley will be examined. Third, some objections will be considered. My own judgment—hopefully not a mere bias—is that Reid did uncover the central thought pattern or one of several perhaps incompatible thought patterns in Berkeley's philosophy.

I

For Reid, first-hand knowledge of current matters of fact is acquired either by consciousness (observation of the mind and its states and activities) or by perception (observation of bodies and their properties and relations). Perceiving is non-inferential belief in the existence of a being having one or more primary or secondary qualities.⁵ Some philosophers treat perception as a situation or process wherein an existent (an object) is given or made present to the perceiver and thus contrast it to belief or judging. Reid, however, held that perception is one of several basic kinds of non-inferential judgment. He rejected the supposition of an infallibly known given, denied that he discovered introspectively an inferential process in perceiving, and claimed that there are no known non-perceptual truths from which a genuine perceptual judgment can be inferred.⁶ Here is Reid on perceiving:

If, therefore, we attend to that act of our mind which we call the perception of an external object of sense, we shall find in it these three things. First, Some conception or notion of the object perceived. Secondly, A strong and irresistible conviction and belief of its present existence. And, thirdly, That this conviction and belief are immediate, and not the effect of reasoning.⁷

If one perceives a die, for example, one not only conceives of a black and white, solid, hard cube, one also affirms its existence, though not as the result of reasoning.

Reid's analysis seems to portray perception as a nonsensuous intellectual operation. This defect was remedied by his doctrine of sensations. Every act of perceiving, he held, is accompanied by or includes one or more sensations.⁸ Having sensations and perceiving are dual responses to stimulation of the same psychological systems. As Reid put it,

We know, that when certain impressions are made upon our organs, nerves, and brain, certain corresponding sensations are felt, and certain objects are both conceived and believed to exist.⁹

Sensations occur constantly and never pass totally unnoticed, even when they are not attended to, that is, when they do not become subjects of beliefs or judgments. Despite their prevalence, sensations are usually misdescribed and mis-classified by philosophers. Some sensations are painful, others decidedly pleasant. To such sensations attention is directed. Consequently, they generally are distinguished from the perceptions they accompany. But with neutral (non-painful non-pleasant) sensations the case is otherwise. They do not become objects of attention. Consequently, they are easily overlooked when perception is analyzed, being either absorbed into the operation of perceiving or equated with its object.¹⁰ For these reasons, Reid considered it important to specify what sensations are.

Two features of sensations as Reid characterized them need to be emphasized. First, in sensations, act and object are one. For Reid, mental states are acts, either volitional acts or cognitive acts. All acts of mind are intentional; that is, for each act an object can be specified. Sensations, though, are unique. In their case, and only in their case, the object intended is not wholly distinct from the act. To illustrate, Reid wrote, “When I am pained, I cannot say that the pain I feel is one thing, and that my feeling it is another thing.”¹¹ In perceiving, say, a cube of sugar, what is perceived, that is, conceived and believed to exist, is not a part or feature of the act of perceiving. But a feeling of pain is a painful feeling. Either the occurrence of the pain is the feeling of it, or the pain is an inseparable part or feature of the feeling of pain. So, too, with all other sensations. Another feature of sensations is that most of the can be placed or located on not one but two continua, the pleasure-pain continuum and a second one involving either different degrees of some sensible qualities or different and complementary sensible qualities. For example, a sensation of touch is either pleasant, painful, or neutral and can equally be classified in terms of the hot-warm-neutral-cool-cold continuum. Another sensation may be sweet and pleasant or overly sweet and so painful. A sound can be described in auditory terms and also as painful; the pain is not a second sensation accompanying the sound; the sound itself is a painful sensation.¹²

Sensations accompany acts of perceiving, Reid claimed. The following may serve to explain what that means.

When I grasp an ivory ball in my hand, I have a certain sensation of touch. Although this sensation be in the mind, and have no similitude to any thing material, yet, by the laws of my constitution, it is immediately followed by the conception and belief, that there is in my hand a hard smooth body of a spherical figure, and about an inch and a half in diameter. This belief is grounded neither upon reasoning nor upon experience; it is the immediate effect of my constitution.¹³

Since it is acknowledged that every perception includes or is accompanied by one or more sensations, why not equate sensations with acts of perceiving or identify sensations as the immediate objects of perception? Reid rejected both suggestions. Sensations are not acts of perceiving because they differ from them in structure. In perceiving, the object of cognition is wholly distinct from the act by which it is cognized. Such is not the case for sensation. Reid insisted,

The form of the expression, I feel pain, might seem to imply that the feeling is something different from the pain felt; yet, in reality, there is no distinction. As thinking a thought is an expression which could signify no more than thinking, so feeling a pain signifies no more than being pained. What we have said is applicable to every other sensation.¹⁴

Sensations, thus, are not acts of perceiving. Nor are they objects of such acts. They are completely different from the material properties and the things possessing those properties which are the objects of perceiving. Though unable to articulate a definition of them, every normal adult knows what solidity is and what pain is and distinguishes the former from the latter.¹⁵ Further, Reid argued, solidity, when conceived, is conceived as in no way implying a sentient being as its subject, while pain is invariably conceived as a state of a sentient being. Where and when pain is, there and then a sentient being is. In Reid's words,

When I am pained, I cannot say that the pain I feel is one thing, and that my feeling it is another thing. They are one and the same thing, and cannot be disjoined, even in imagination. Pain, when it is not felt, has no existence. It can be neither greater nor less in degree or duration, nor any thing else in kind, than it is felt to be. It cannot exist by itself, nor in any subject, but in a sentient being. No quality of an inanimate insentient being can have the least resemblance to it.¹⁶

What holds for pains and pleasures, Reid insisted, holds for all sensations. None is an object of perception, since the latter yields direct knowledge and empirical inferences concerning insentient beings and their states, but sensations neither are insentient beings nor states of such. They exist only in sentient beings or minds.

Reid credited Berkeley with having a precise and accurate conception of sensations, that is, of meaning by “sensation” what he, Reid, meant by it. He praised Berkeley for avoiding Locke's errors, writing,

As there can be no notion or thought but in a thinking being; so there can be no sensation but in a sentient being. It is the act, or feeling of a sentient being; its very essence consists in its being felt. Nothing can resemble a sensation, but a similar sensation in the same, or in some other mind. To think that any quality in a thing that is inanimate can resemble a sensation, is a great absurdity.¹⁷

Berkeley's mistake, Reid maintained, was in conflating the sensations which accompany acts of perceiving with the objects of those acts. This inevitably led to the conclusion that sensations are the sole objects of perception. Reid conceded that if this premise is granted, Berkeley's attack on material substance cannot be blocked. The premise need not, however, be granted. In fact, Reid argued, it must not be granted. He wrote,

Suppose I am pricked with a pin; I ask, is the pain I feel, a sensation? undoubtedly it is. There can be nothing that resembles pain in any inanimate being. But I ask again, is the pin a sensation? To this question I find myself under a necessity of answering, that the pin is not a sensation, nor can have the least resemblance to any sensation. The pin has length and thickness, and figure, and weight. A sensation can have none of those qualities. I am not more certain that the pain I feel is a sensation, than that the pin is not a sensation; yet the pin is an object of sense; and I am as certain that I perceive its figure and hardness by my senses, as that I feel pain when pricked by it.¹⁸

The point of Reid's criticism is obvious. It is equally obvious that it is unwarranted unless Berkeley meant by “idea of sense” what Reid meant by “sensation.” To this question we must now turn.

II

Although, strictly speaking, it is not relevant to proving that Berkeley construed ideas of sense as sensations, in Reid's sense of the term, his tendency to use the two terms interchangeably in the Philosophical Commentaries, Principles of Human Knowledge, and Three Dialogues between Hylus and Philonous is worth noting. From the first, there is this example.

Extension itself or anything extended cannot think these being mere ideas or sensations whose essence we thoroughly know.¹⁹

From the Principles, this:

If we had a new sense, it could only furnish us with new ideas or sensations: and then we should have the same reason against their existing in an unperceiving substance, that has been already offered with relation to figure, motion, colour, and the like. Qualities, as hath been shown, are nothing else but sensations or ideas, which exist only in a mind perceiving them.²⁰

And from the Three Dialogues, this:

The things, I say, immediately perceived, are ideas or sensations, call them which you will. But how can any idea or sensation exist in, or be produced by, any thing but a mind or spirit.²¹

The next question, which is the real question, is whether or not Berkeley construed ideas, that is, sensations, as Reid did.

A Berkeleyan idea of sense (sensation) agrees with a Reidian sensation in being incapable of existing unperceived (unfelt, unsensed). But is this common position founded on a shared conception of the nature of sensations? Of the four reasons to be given below for the affirmative, three are based on straightforward textual comparisons and the fourth is an argument from the occurrence of a rather unusual argument in Berkeley's campaign to prove the non-existence of material substances.

Berkeley, like Reid, made pleasures and pains paradigmatic of sensations (entities which cannot exist unfelt) and attempted to reduce qualities perceived by the several senses to them. The following exchange between Hylas and Philonous is a familiar example.²²

Phil: But is not the most vehement and intense degree of heat a very great pain?

Hylas: No one can deny it.

Phil: And is any unperceiving thing capable of pain or pleasure?

Hylas: No certainly.

Phil: Is your material substance a senseless being or a being endowed with sense and perception?

Hylas: It is senseless without doubt.

Phil: It cannot therefore be the subject of pain.

Hylas: By no means.

Phil: Nor consequently of the greatest heat perceived by sense, since you acknowledge this to be no small pain.

Hylas: I grant it.

Berkeley's earnestness in introducing this argument is evidenced by his handling of Hylas's attempt to cancel his original concession that an intense heat is a pain. Note that in the following exchange Philonous argues that pain and pleasure cannot be felt or conceived as distinct from some type of sensible quality and so are intense degrees of those sensations. The passage reads:

Phil: Upon putting your hand near the fire, do you perceive one simple uniform sensation, or two distinct sensations?

Hylas: But one simple sensation.

Phil: Is not the heat immediately perceived?

Hylas: It is.

Phil: And the pain?

Hylas: True.

Phil: Seeing therefore they are both immediately perceived at the same time, and the fire affects you only with one simple, or uncompounded idea, it follows that this simple idea is both the intense heat immediately perceived and the pain; and consequently, that the intense heat immediately perceived, is nothing distinct from a particular sort of pain.

Hylas: It seems so.

Phil: Again, try in your thoughts, Hylas, if you can conceive a vehement sensation to be without pain, or pleasure.

Hylas: I cannot.

Phil: Or can you frame to yourself an idea of sensible pain or pleasure in general, abstracted from every particular idea of heat, cold, tastes, smells? etc.

Hylas: I do not find that I can.

Phil: Doth it not therefore follow, that sensible pain is nothing distinct from those sensations or ideas, in an intense degree.

Hylas: It is undeniable; and to speak the truth, I begin to suspect a very great heat cannot exist but in a mind perceiving it.²³

One realizes the significance of this exchange if one recalls that in Section 8 of the Principles, Berkeley argued that just as ideas cannot exist unperceived, so nothing like an idea can exist unperceived, and notices that in the context of the above exchange he goes on to make the same point.

Phil: … Tell me, whether in two cases exactly alike, we ought not to make the same judgment?

Hylas: We ought.

Phil: When a pin pricks your finger, doth it not rend and divide the fibres of your flesh?

Hylas: It doth.

Phil: And when a coal burns your finger, doth it any more?

Hylas: It doth not.

Phil: Since therefore you neither judge the sensation itself occasioned by the pin, nor any thing like it to be in the pin, you should not, conformably to what you have now granted, judge the sensation occasioned by the fire or any thing like it, to be in the fire.²⁴

Reid, as was noted above, treated feelings of pain and pleasure as paradigms of sensations. Berkeley attempted to construe immediate objects of sense in terms of the same feelings. We have then some evidence that Berkeley's ideas of sense were understood along the same lines as Reid's sensations.²⁵

It will be recalled that Reid was insistent that in sensations one cannot distinguish what is sensed from the sensing of it. Berkeley's ideas of sense are no different. In the Principles, Section 5, he states,

Hence as it is impossible for me to see or feel anything without an actual sensation of it, so it is impossible for me to conceive in my thoughts any sensible thing or object distinct from the sensation or perception of it.

In the Three Dialogues, Philonous shreds Hylas's attempt to invoke the act-object distinction. His chief argument is the questionable one that since there is no willing of what one senses, there is no action in a sensation. However, he does make the following point as a supplement to his main argument.

Phil: Besides, since you distinguish the active and passive in every perception, you must do it in that of pain. But how is it possible that pain, be it as little active as you please, should exist in an unperceiving substance. In short, do but consider the point, and then confess ingeniously, whether light and colour, tastes, sounds, etc., are not all equally passions or sensations in the soul.²⁶

Whether or not one accepts his arguments for the thesis, one must at least acknowledge that Berkeley did deny the act-object distinction in the case of sensations and did fall back on the case of pain to make clear his own position. Here, too, his account of ideas of sense anticipates Reid's characterization of sensations. Here, too, then, Reid's interpretation is corroborated.

For Reid, the occurrence of a sensation is the occurrence of an episode in the history of a sentient being. A sensation cannot occur in an insentient or inanimate object.²⁷ Thus, not only must a sensation be felt in order to exist, it must also occur as a state of a consciousness, a mind, a sentient thing. Once again, it is not difficult to link Berkeley and Reid, since throughout the Principles and Three Dialogues Berkeley says of ideas of sense both that they cannot exist unperceived and that they cannot exist in an unperceiving or insentient being.²⁸ In Section 9 of the Principles, he argued against the possibility of material substances, as defined by the new (mechanistic) philosophers on the basis of the second, not the first, claim. His argument, that is, is not that figure, for example, cannot exist unperceived and so cannot be in or a part of an unperceived substance. Instead, Berkeley argued,

By matter therefore we are to understand an inert, senseless substance, in which extension, figure, and motion, do actually subsist. But it is evident from what we have already shown that extension, figure and motion are only ideas existing in the mind, and that an idea can be like nothing but another idea, and that consequently neither they nor their archetypes can exist in an unperceiving substance. Hence it is plain, that the very notion of what is called matter or corporeal substance, involves a contradiction in it.²⁹

Berkeley's argument is really quite peculiar. Note that if one takes the phrase “extension, figure and motion are only ideas existing in the mind” to mean “extension, figure and motion must be perceived to exist,” the conclusion drawn does not follow. So long as they are perceived by another being, X, instances of extension, figure, and motion could exist in an unperceiving thing, Y. Unless, of course, they are construed as states of mind, episodes in the history of a sentient thing. In that case, to have extension is to perceive it, and that is impossible for an unperceiving thing. That this is what Berkeley intended is strongly suggested by his first demonstration of the impossibility of material substance in Section 7 of the Principles. There he wrote,

From what has been said, it follows, there is not any other substance than spirit, or that which perceives. But for the fuller proof of this point, let it be considered the sensible qualities are colour, figure, motion, smell, taste, and such like, that is, the ideas perceived by sense. Now for an idea to exist in an unperceiving thing, is a manifest contradiction; for to have an idea is all one as to perceive: that therefore wherein colour, figure, and the like qualities exist, must perceive them; hence it is clear there can be no unthinking substance or substratum of those ideas.

On this view, esse est percipi states not just that for a sensible quality to exist it must be perceived, but also that its existence (its occurrence) is the perception of it. The occurrence of a sound is the occurrence of the hearing (the perception) of that sound. Its occurrence is the occurrence of a perceiving and of an object perceived. Its occurrence is an episode in the existence of a sentient being, that which is said to perceive the sound. Small wonder, then, that Berkeley insisted that no inanimate and unperceiving thing can have or be like a sound. The only thing like a sensation (a sound) is a sensation (a sound); the only thing that can have a sensation is a sentient thing (a mind).

If one interprets Berkeley along the lines we've recommended, one can discover historical antecedents for his doctrine of sensations without much difficulty. The “New Philosophers” generally construed colours, sounds, odours, tastes, and various tactile qualities as responses in consciousness to physical-physiological transactions. As early as the Assayer (1623), Galileo argued that heat is no more in the fire that causes us to feel it than a tickle is in the feather which brushes one's armpit.³⁰ Such diverse thinkers as Descartes, Rohault, Malebranche, Boyle, and Locke used “sensation” for immediately experienced objects, sounds, colours, and the like, which were denied extra-mental existence.³¹ As scientists, they extruded from the external world whatever was not susceptible of a mechanistic explanation. The reduction of sensed qualities to the level of feelings of pleasure and pain guaranteed that extrusion. Here is Locke on the topic:

And yet he that will consider that the same fire that at one distance produces in us the sensation of warmth does, at a nearer approach, produce in us the far different sensation of pain, ought to bethink himself what reason he has to say that his idea of warmth, which was produced in him by the fire, is actually in the fire; and his idea of pain, which the same fire produced in him in the same way is not in the fire.³²

A. A. Luce maintains that Berkeley merely exploited these positions by purely ad hominem arguments to the effect that the mechanists themselves provide grounds for denying that material substances exist or are knowable.³³ But to so argue is to ignore two important truths. The first is that the sensationalistic characterization of objects of sense does not presuppose mechanism or the so-called corpuscularian philosophy of Boyle and Locke. Consequently, Berkeley could retain the former while rejecting the latter. The second is that having refuted the indirect realism—the unperceived material substances—of the new philosophers, Berkeley did not opt for naive or direct realism. He denied that material substances (unperceiving beings capable of unperceived existence) are immediate objects of sense, and he did so on the grounds that no immediate object of sense can exist unperceived. Consequently, one can hardly hold that Berkeley asserted the last solely as an ad hominem argument against the new philosophers.

III

Now for a few objections. First, one might be inclined to argue that my interpretation must be wrong because Berkeley would never have maintained the absurd view that extension is on a par with feelings of pleasure and pain. Such confidence may be unwarranted. Admittedly, one cannot quote Berkeley to the effect that in perceiving extension sensations of pleasure and pain are invariably felt, but he did maintain

Extension a sensation, therefore not without the mind.

Extension abstract from sensible qualities is no sensation, I grant, but then there is no such idea as any one may try. There is only a considering the number of points without the sort of them, & this makes more for me, since it must be in a considering thing.³⁴

Moreover, he had Philonous explain why philosophers distinguished between secondary and primary qualities as follows:

Heat and cold, tastes and smells, have something more visibly pleasing or disagreeable than the ideas of extension, figure and motion, affect us with. And it being too visibly absurd to hold, that pain and pleasure can be in an unperceiving substance, men are more easily weaned from believing the external existence of the secondary than the primary qualities. You will be satisfied there is something in this, if you recollect the difference you made between an intense and a more moderate degree of heat, allowing the one a real existence, while you denied it to the other. But after all, there is no rational ground for the distinction, for surely an indifferent sensation is as truly a sensation, as one more pleasing, or painful; and consequently should not be any more than they be supposed to exist in an unthinking subject.³⁵

It is far from clear just how Berkeley analysed extension, since he denied that it is immediately perceived by both sight and touch and hinted that it is reducible to arrangements of minimum visibles or minimum tangibles. Because of the intricacies of Berkeley's position on the perception of distance, shape, location, and magnitude, it is perilous to dictate what he could not have meant when he insisted that extension cannot exist unperceived.

Next we must consider our interpretation in terms of Section 49 of the Principles. There Berkeley poses the following objection.

[I]f extension and figure exist only in the mind, it follows that the mind is extended and figured; since extension is a mode or attribute, which (to speak with the Schools) is predicated of the subject in which it exists.

He replied,

I answer, those qualities are in the mind only as they are perceived by it, that is, not by way of mode or attribute, but only by way of idea; and it no more follows, that the soul or mind is extended because extension exists in it alone, than it does that it is red or blue, because those colours are on all hands acknowledged to exist in it, and no where else.

It is clear that Berkeley denies that for him a mind's perceiving a quality is that quality's being a mode or attribute inhering in that mind. Does the interpretation at hand conflict with this stricture? I think not. According to the interpretation, an occurrence of a pain or an instance of blue is, as such, a feeling of pain or a sensing of blue. Whatever the relation between sensations and minds is—and it is far from obvious what it is—it is not the basis for sensing. Even if sensations are construed as modes or attributes, it would be correct to say that blue is in the mind by way of sensation since an occurrence of blue is a sensing of blue, i.e., a sensation.

Finally, what of Berkeley's insistence that he transformed ideas into things, not things into ideas.³⁶ That is, what of Luce's contention that since Berkeley insisted he did not reject bodies in rejecting material substance, he remained a mind-body dualist and, therefore, could not have intended to reduce bodies to states of mind.³⁷ It is undeniable and so must be conceded that Berkeley did attempt to secure the reality of bodies and our knowledge of them. But does this mean that his position precludes Reid's interpretation of his ideas of sense? It is far from obvious that it does. In the first place, the crucial step in the transformation of ideas into things is the attempt to demonstrate the impossibility of imperceptible material substances. So long as the latter are posited, the immediate objects of sense are construed as appearances. A colour seen and a sound heard are, at best, accurate copies of things. The first and crucial step in considering those sensibles as things, not images, is eliminating the objects behind the scenes. Berkeley's demonstration of the impossibility of imperceptible material substances utilizes the thesis that the immediate objects of sense cannot exist unperceived. Consequently, it is difficult to see how the transformation of ideas into things could require repudiation of that thesis. Now a second point. The contrast between the real and the imaginary is drawn among immediate objects of sense. The real is defined in terms of lawful connections among sense objects as well as their intensity, distinctness, and involuntariness.³⁸ All are features and relations sensations can have. The point is that an immediate object of sense, though understood as a sensation, can be part of a class of such objects which meet the requirements for being a real thing. In the third place, Berkeley did retain the mind-body distinction, but only as more-or-less equivalent to his sharp distinction between perceivers and sensibles. He jettisoned the dualism of mental substances and physical (material) substances. Sensible objects are both causally and perceptually dependent upon perceiving minds, and imperceptible matter is a philosophical fiction. This position does not preclude mind-body dualism, however, so long as knowledge of bodies can be analysed in terms of sensibles, that is, sensations. In sum, we may say that Berkeley's handling of his claim to have retained knowledge of bodies and, so, the reality of bodies does not show that for him the immediate objects of sense are not sensations. Whether Berkeley's handling of his claim is philosophically satisfactory is, of course, another and more important question.

Notes

1. The source for all quotations from and references to writings of Berkeley is The Works of George Berkeley, ed. by A. A. Luce and T. E. Jessop, 9 vols. (London: Nelson and Co., 1948). Whenever possible, citations will specify a particular work and section thereof; otherwise, a volume and page of the Luce and Jessop edition will be cited following the name of the writing cited or quoted.

2. This position is defended in E. B. Allaire, “Berkeley's Idealism,” Theoria 29 (1962-63): 229-44, and Phillip D. Cummins, “Perceptual Relativity and Ideas in the Mind,” Philosophy and Phenomenological Research 24 (1963): 202-14.

3. This, perhaps, is what W. H. Hay is suggesting in his “Berkeley's Argument from Nominalism,” Revue Internationale de Philosophie 7, fasc. 1-2 (1953): 19-27.

4. Thomas Reid, Essays on the Intellectual Powers of Man, ed. by B. Brody (Cambridge, Mass.: MIT Press, 1969), II.xi, pp. 190-91. It may prove helpful to provide cross references to Thomas Reid's Philosophical Works, ed. by Sir William Hamilton, 2 vols., second edition (Hildescheim: Olms Verlagsbuchhandlung, 1967). In this instance, see Works, I, p. 289.

5. Reid, Essays, I.i, pp. 8-10; II.v, pp. 111-18; II.xvii, pp. 252-75. Reid, Works, I, pp. 222, 258-60, and 313-38.

6. This contention is argued at length in my “Reid's Realism,” Journal of the History of Philosophy 12 (1974): 317-40.

7. Reid, Essays, II.v, pp. 111-12; Reid, Works, I, p. 258.

8. Reid, Essays, II.xvi, p. 242; Reid, Works, I, p. 310.

9. Reid, Essays, II.xx, p. 288; Reid, Works, I, p. 327.

10. Reid, Essays, I.i, p. 23; II.xvi, pp. 244-49. Reid, Works, I, pp. 229, 311-13.

11. Reid, Essays, I.i, p. 27; Reid, Works, I, p. 229. See also Reid, Essays, II.xi, p. 197; Reid, Works, I, p. 292.

12. Reid, Essays, II.xvi, pp. 244-47; Reid, Works, I, pp. 311-12.

13. Reid, Essays, II.xxi, p. 302; Reid, Works, I, p. 332.

14. Thomas Reid, An Inquiry into the Human Mind on the Principles of Common Sense (1764), VI.xx (in the Hamilton edition, I, p. 183).

15. Reid, Essays, II.xi, pp. 192-93; II.xvi, pp. 249-50; II.xvii, pp. 252-55. Reid, Works, I, pp. 290, 312-14.

16. Reid, Essays, I.i, p. 27; Reid, Works, I, p. 229. See also Reid, Essays, II.xvi, pp. 243-44, 249; Reid, Works, I, pp. 310, 312.

17. Reid, Essays, II.xi, p. 191; Reid, Works, I, pp. 289-90.

18. Reid, Essays, II.xi, pp. 192-93; Reid, Works, I, p. 290.

19. Philosophical Commentaries, Sect. 34. See also Sects. 249, 280, 286, 377, 440, and 666.

20. Principles, Sect. 78. See also Sects. 3-5, 18-20, 25, 32, 74, 81, 90, 136-37, 146, 148, and 149 for the use of “idea of sensation,” showing the interchangeability of the two terms.

21. Berkeley, Works, II, p. 215. See also pp. 176-77, 187-88, 201, 203-4, 206, and 248-49.

22. Three Dialogues, in Berkeley, Works, II, p. 176.

23. Three Dialogues, in Berkeley, Works, II, pp. 176-77.

24. Three Dialogues, in Berkeley, Works, II, p. 179.

25. For some further examples, see Berkeley, An Essay toward a New Theory of Vision, Sect. 41; Principles, Sect. 41; and Three Dialogues, in Berkeley, Works, II, pp. 180, 191-92, 197, and 240-41.

26. Three Dialogues, in Berkeley, Works, II, p. 197. As my colleague, Laird Addis, pointed out to me, Berkeley does not directly consider in this context whether a sensation can be analysed into act and object. From the point at which Hylas introduces the topic, the issue is whether immediate perception can be analysed into sensation (an act of mind) and object of sense. It is clear that Berkeley would resist all attempts to analyse sensations into acts and their objects, given his implicit concession that a genuine act-object distinction would provide grounds for questioning the dependence of the object and his criteria for identifying acts. For Berkeley, perception is the occurrence of a sensation. He rejects attempts to find in perception an act (called sensation) and an object. So clearly he cannot admit to finding an act and object in sensation.

    There is another interesting point to be made. It is that Reid was free to speak of sensations (states of sentient beings) as acts whose objects cannot be distinguished from them, since he did not make volition a necessary condition of activity. Berkeley did lay down that condition (see pp. 196-97). He thus could not speak of sensations as acts, as Reid later did, even though he too took sensations to be states of sentient beings.

27. Reid, Essays, II, xi, p. 191; Works, I, pp. 289-90.

28. Cf. Principles, Sects. 15, 41, 45, 76, 78, and 91; see also Three Dialogues, in Berkeley, Works, II, pp. 175-76, 177, 181, 191-92, 195, 197, and 237.

29. Principles, Sect. 9.

30. See Galileo, “A Letter to the Illustrious and Very Reverend Don Virginio Casarini,” in The Philosophy of the 16th and 17th Centuries, ed. by R. H. Popkin (New York: The Free Press, 1966): 65-68.

31. On Descartes, see his Le Monde, Chs. I and II of the essay on light, De la Lumiere; see his The Philosophy of Descartes, trans. and ed. by H. A. P. Torrey (New York: Holt, 1892), pp. 207-14. For Rohault, see the entry under “sensation” in the Dictionnaire François, ed. by C. P. Richelet (Geneva: Widerhold, 1680). For Boyle, see the Oxford English Dictionary (Oxford: Clarendon Press, 1933), entry for “sensation.” For Locke, see his Essays Concerning Human Understanding, II.viii.16. For Malebranche, see, for example, his De la recherche de la vérité, VI.ii.2, and the T. Taylor translation (1700) of that chapter. Taylor used “sensation” for Malebranche's “sentimen.”

32. Locke, Essays Concerning Human Understanding, II.viii.16.

33. Berkeley, Works, II, p. 192 n. 1.

34. Philosophical Commentaries, Sects. 18 and 440.

35. Three Dialogues, in Berkeley, Works, II, pp. 191-92.

36. Principles, Sects. 38-39.

37. A. A. Luce, Berkeley's Immaterialism (London: Nelson, 1945), chs. 1, 3-5.

38. Principles, Sects. 28-33, 36, and 40-41.