BERKELEY: AN OVERVIEW
Berkeley argues for a collection of related theses: that the only things that exist are minds and ideas in them; that there is no such thing as material substance; that all the qualities or properties of objects, and indeed the objects themselves, are nothing but ideas, nothing but mental entities.
Locke agrees with Descartes that there are mental substances, and that ideas are phenomena that occur in mental substances; and he agrees that there are physical substances, and that primary qualities are features of these physical substances. But then, for Locke as for Descartes, there are also secondary qualities, which hover uneasily between ideas and primary qualities; sometimes Locke seems to regard these as just ideas in our minds, while at other times he adopts what is probably his considered view, namely that they are powers to produce a certain sort of idea in us. This sets up Berkeley's problematic, since a large part of Berkeley's concern is with the location of qualities; Berkeley, unlike Locke, identifies all qualities with ideas and locates them in the mind.
It is useful to begin discussing Berkeley with his definition of the notion of a "sensible thing." In the Dialogues, Berkeley defines sensible things as things which are perceived by the senses (137 ; quotations from Berkeley's Principles will be by section number, and those from the Dialogues to pages in David Armstrong, ed., Berkeley's Philosophical Writings, with bracketed references to Steven M. Cahn, ed., Classics of Western Philosophy, 3rd Edition). But he quickly goes on to add that "the senses perceive nothing which they do not perceive immediately: for they make no inferences (138 )," so a sensible thing is a thing immediately perceived by sense, where "immediately perceived" means "perceived without inference."
But Berkeley immediately proceeds to cheat, since his examples of sensible things are sensible qualities like heat and color. Many people not already committed to Berkeley's idealism will want to insist that such qualities are not perceived immediately, but rather are perceived mediately or indirectly in virtue of perceiving mental phenomena. Certainly this was Locke's view, and Locke is one of Berkeley's primary targets, so Berkeley ought at least to take this view seriously. But he seems not to.
Berkeley often seems to trade unfairly on the difference between the ordinary sense of "sensible object" and his rather technical one. This gives him a very quick argument for his idealism. For example, after noting that it is "an opinion strangely prevailing amongst men, that houses, mountains, rivers, and in a word all sensible objects, have an existence . . . distinct from their being perceived," Berkeley asserts that this view involves "a manifest contradiction. For, what are the forementioned objects but the things we perceive by sense? and what do we perceive besides our own ideas or sensations? and is it not plainly repugnant that any one of these . . . should exist unperceived?" (Principles, §4). Berkeley gets assent to the view that houses, e.g., are sensible things, by using the term "sensible thing" in a nontechnical sense, then uses his special sense of the term in insisting that we perceive only our own ideas or sensations. But this moving back and forth is illegitimate. His opponents will insist that houses are not sensible objects in the technical sense, while in the nontechnical sense we do perceive things other than our own ideas. (A similar unfairly fast argument occurs in §7.)
Some of Berkeley's other arguments may be characterized as follows.
B. Arguments that secondary qualities are mental
Berkeley offers several arguments that secondary qualities exist only in people's minds, many of them reminiscent of Locke's arguments for the subjectivity of the secondary qualities. For example, Berkeley offers (1) the argument from pleasures and pains (Dialogues 139-41 [720-721]). Berkeley points out that if we touch something very hot, a rock, say, we get only a single sensation, which is both a sensation of heat and a sensation of pain. He infers that an extreme heat is a pain. Since rocks cannot feel pain, rocks cannot have extreme heat.
It seems fairly obvious what to say here. Berkeley fails to distinguish the property of being hot from the property of having sensations of heat. Making this distinction gives us two versions of the argument. The first version moves from the true (let us suppose) premises that a sensation of extreme heat is a sensation of pain and that rocks cannot have pain to the harmless conclusion that rocks cannot have sensations of extreme heat. The second version moves from the premises that an extreme heat is a pain and that rocks cannot feel pain to the conclusion that rocks cannot have extreme heat; this is the conclusion Berkeley wants, but the first premise seems obviously false. Certainly once the distinction is made the first premise does not follow from the evidence Berkeley cites about the identity of sensations.
Is Berkeley's failure to make the obvious distinction between sensations and the qualities which produce them and which they represent a simple confusion? Sometimes it appears so. But Berkeley does occasionally defend it. One such defense is an analogy he draws between heat and pain (Principles section 41; Dialogues 143 ; Locke draws a similar analogy [Essay II.viii.18]). Berkeley points out that when we get a pin prick we have a pain sensation and when we feel a fire we have a heat sensation. But we do not say the pain is in the pin; by analogy we ought not to say the heat is in the fire. But Berkeley misses a crucial difference here. A sensation of pain is a pain, but a sensation of heat is not heat. The sensation of pain is not in the pin, but the power to produce that sensation is, just as, while the sensation of heat is not in the fire, the power to produce that sensation is. The difference is just that we call the power to produce heat sensations "heat" but do not call the power to produce pain sensations "pain."
A second attempt on Berkeley's part to show that there cannot be a distinction between sensations and qualities occurs in the First Dialogue (158-60 ). Hylas, the materialist, protests that he has failed to "sufficiently distinguish the object from the sensation." But, frustratingly, Berkeley has Hylas add that the sensation is "an act of the mind," and Berkeley's spokesman Philonous convinces Hylas that sensations cannot be acts because they do not involve volition.
So much for the argument from pleasures and pains. A second main argument that secondary qualities are mental is (2) the argument from perceptual relativity (at e.g. Dialogues 142-3 [722-23]). One instance of the argument involves an example in which someone heats one hand and cools the other; plunging both into lukewarm water, the subject discovers that one hand perceives the water to be cool and the other perceives it to be warm. We may reconstruct the argument like this: (1) if something feels hot, it is hot; (2) if something feels cold, it is cold; (3) this water feels both hot and cold. From these premises it follows that (4) this water is both hot and cold. But nothing can be simultaneously hot and cold, so the conclusion is false. Berkeley thinks the argument shows that if there were material substances, they would have contradictory properties; since this is impossible there must be no such thing as material substances. But a more straightforward response would be that, since the conclusion is false and the argument is valid, one or more of the premises must be false--and indeed both (1) and (2) are likely candidates, since they obliterate the distinction between apparent temperature and actual temperature. (I take Berkeley's argument from microscopes, Dialogues 148-9 [726-28], to be a species of perceptual relativity argument.)
C. arguments that primary qualities are mental
In both the Principles and the Dialogues, Berkeley offers a number of arguments that the primary qualities are mental. For the most part these simply parallel his arguments for the secondary qualities, especially perceptual relativity arguments. He summarizes these arguments this way: "let any one consider those arguments which are thought manifestly to prove that colors and tastes exist only in the mind, and he shall find they may with equal force be brought to prove the same thing of extension, figure, and motion" (Principles §15).
We have seen that these relativity arguments do not show what Berkeley things they show, namely that qualities are in people's minds, not in external objects. But perhaps they do show something. We saw we could avoid Berkeley's conclusion by distinguishing between actual qualities and apparent qualities, and noting that perception is not always veridical. But surely there is a sense of perception in which it must be veridical, in which we could not be mistaken about what we perceive. We perceive something we may be mistaken about, the actual quality of an object, by perceiving something we cannot be mistaken about, the apparent qualities of the object. We might say that what we immediately perceive are the apparent qualities. But then the perceptual relativity arguments do at least show that the apparent qualities of objects cannot be in the objects themselves.
We may, then, regard Berkeley as having at this point shown that the immediate objects of perception are mental. He has not yet shown that there are no qualities in external objects, but the present point together with arguments that there is nothing beyond what we immediately perceive, would have that conclusion. And indeed Berkeley proceeds to provide just such arguments.
D. Arguments that the notion of material substance is meaningless
Berkeley heaps scorn on Locke's notion of substance. (See especially Principles §§16-17 and §§178-9, and Dialogues 161-63 [736-37] and 178-9 .) His principal criticism is one with which Locke would have had considerable sympathy--namely, that we simply have no coherent idea of substance. Berkeley, by the way, calls Locke's notion of substance "material substance," or sometimes simply "matter." Berkeley has Philonous ask Hylas, "You have no idea at all, neither relative nor positive, of Matter; you know neither what it is in itself, nor what relation it bears to accidents (i.e. properties)?" And Hylas says "I acknowledge it" (162 ). And Berkeley thinks that this shows that when Locke asserts that matter exists, he doesn't mean anything coherent at all. As Philonous says, speaking of Hylas' (and Locke's) conception of matter, "in all your various senses, you have been shewed either to mean nothing at all, or, if anything, an absurdity. And if this be not sufficient to prove the impossibility of a thing, I desire you will let me know what is." And Hylas responds, "I acknowledge you have proved that Matter is impossible; nor do I see what more can be said in defense of it" (189 ).
Let us explore this matter in a bit more detail. Remember that Locke's notion of substance is the notion of whatever it is that supports the primary and secondary qualities--or rather, the primary qualities, since Locke thinks that the secondary qualities are just powers that the objects have because of their primary qualities. Remember too that Locke admits that we do not have a clear idea of substance; he calls it a "something I know not what." If asked what has the property of redness, Locke could answer, "a solid, extended thing;" but if asked what has the properties of solidity and extension, he can only say "something, I know not what."
Now let us turn to Berkeley's criticism of the idea of substance. Berkeley asks: where do you get the idea of substance in general? (161  on "material substratum".) You cannot get it from sensation, since that only gives us the ideas of properties of objects. But also it seems that we can't get it from watching our own minds at work. For Locke and Berkeley these two sources exhaust our sources of ideas. So Berkeley suggests that this notion of substance-in-general is a fraud, a term with no genuine idea corresponding to it, and hence a meaningless term. Berkeley goes on to conclude that if the notion of an external substance which possesses properties makes no sense, then we are better off just thinking of "sensible qualities" as in the mind rather than in substances or external objects. (Notice, by the way, that precisely the same problems ought to attend the notion of mental substance as attend the notion of material substance: no matter how much we introspect we capture only properties or characteristics of our minds, not mental substance itself; mental substance seems to be just a "something I know not what" for ideas to inhere in just as physical substance is a something I know not what for properties to inhere in. In fact Berkeley agrees that we cannot have an idea of mental substance any more than we can have an idea of material substance, but for no particularly good reason insists that we have "notions" of mental substances.)
Two comments are in order about this Berkeleian argument against material substance. First, part of what is needed here is surely a better account of concept formation than Locke and Berkeley's empiricist one. It seems insufficient to think of all concepts as just copies of sense impressions. We need to find room for more intellectual or creative activity than that, and Kant will help to provide such a richer account.
But second, even waiving empiricist difficulties about how we could acquire the notion of material substance, the notion itself seems rather mysterious. There is something puzzling about the notion of substance as whatever it is that supports or possesses properties. (I myself continue, perhaps perversely, to find it disturbing.) But perhaps some of the mystery can be dispelled as follows.
Locke and Berkeley seem to work backward in an odd sort of way. They say: look, we've got all these ideas of qualities; but then the qualities require something to support them. But isn't there something quite unrealistic about this picture of us as finding ourselves equipped with lots of ideas of properties but casting about in perplexity for whatever has the properties? The idea of red, for example, is not an idea of a property at all unless it is already an idea of something objects have (rather than just an idea of something in the mind). We don't really get all these ideas of properties and then try to build ideas of objects out of them; we notice all these objects wandering around and then start trying to find ways to categorize them. Properties are the ways we find to group or categorize objects. And terms like 'substance', 'object', 'thing' are just the most general ways of classifying objects: the classification that includes all of them.
E. Arguments that there is no reason to believe in material substance
We have spent a good deal of time on Berkeley's criticism of the notion of substance. I shall be briefer about some remaining matters. Another argument Berkeley offers for the view that there is nothing but what we are immediately aware of in perception is the argument that we have no reason to believe anything else exists. (See Principles §§18-19; Dialogues 166-70 [740-42].) Berkeley raises two related considerations here. First, he suggests that there is no way we could come to learn about anything except the immediate objects of sense, since we can perceive nothing else directly, can construct no a priori argument for the existence of anything else, and cannot learn that certain kinds of experience are reliably correlated with anything else (since we cannot notice a certain kind of experience, notice some objective property of material substance, and then notice that the one is always accompanied by the second: all we ever perceive, on Berkeley's account, are items of the former sort). Second, Berkeley points out that it is unnecessary to postulate the existence of material substance, since our experiences could be exactly the same whether there were any nonmental cause of them or not. In both cases, Berkeley seems severely hampered by the absence of any notion of inference to the best explanation.
F. Berkeley on perception
I turn finally to some general remarks on Berkeley's view of perception. Locke held, as we have seen, that intentional (representational) and phenomenal things are both mental. And his paradigm mental object, the "idea," he thinks of as a kind of mental image with both sorts of property. Indeed Locke seems to think that the intentional properties depend on the phenomenal ones--that ideas represent objects because they resemble them. Berkeley helps us to see the difficulties and perplexities into which this view drags us by his negative example. Here are two examples.
(i) The first difficulty with the view is that it makes perception seem too passive. Thus Berkeley arrives at the view that immediate perception is completely passive--that, as he puts it, "the senses make no inferences." This makes perception look too much like simply absorbing information.
We will see a much more sophisticated view of perception in Kant. But for now consider an example which should make us suspicious of this view of perception, skeptical of the view that there is any such thing as "immediate perception." Consider this box:
and notice (a) that it is difficult or impossible to see it as merely a two-dimensional array of lines, (b) that it can be seen as two different 3-dimensional cubes, depending on which face is seen as closest to the viewer, and (c) that it looks different depending on which way it is interpreted. The moral is that how things look, the very phenomenological character of our experience, already depends on inference and interpretation. (Compare Putnam on the rainbow in Reason, Truth and History.)
(ii) A second difficulty with a view of perception and thought which regards ideas as a kind of mental image is that it makes it too easy to confuse phenomenal properties of my sensations or images with properties of the objects they represent. Many of Berkeley's arguments seem to involve such a confusion. For example, Berkeley seems to confuse the phenomenal feeling or sensation of heat, the way we feel when we touch something hot, with the property of heat itself; otherwise he could not think that the fact that rocks do not have sensations shows that they do not have heat, or that there is an illuminating comparison between heat and pain.
(iii) A final difficulty with Locke's passive view of perception is one which Berkeley himself explicitly points out. On the Lockean view, what enables an "idea" or mental image to represent an object is that the idea resembles the object. (Remember Locke's claim that ideas of primary qualities are "resemblances" of the things themselves.) But Berkeley quite rightly points out that this is silly. Ideas of primary qualities no more resemble the object than ideas of secondary qualities do. As Berkeley has Hylas finally admit, "I find it impossible for me to conceive or understand how anything but an idea can be like an idea" (Dialogues, 170 ).
As so often, though, we may want to draw a different conclusion from this than Berkeley did. Berkeley thought that (1) ideas cannot be like non-ideas, (2) ideas are in the mind, and (3) if an idea were to represent something, it would have to resemble it. Berkeley concludes that ideas cannot represent anything nonmental. We may be inclined to reject Berkeley's (and Locke's) premise (3).