It will probably be known to all of you that the {12} first person to make this momentous inference was Bishop Berkeley. There was, indeed, an obscure medieval schoolman, hardly recognized by the historians of Philosophy, one Nicholas of Autrecourt, Dean of Metz,[3] who anticipated him in the fourteenth century, and other better-known schoolmen who approximated to the position; and there are, of course, elements in the teaching of Plato and even of Aristotle, or possible interpretations of Plato and Aristotle, which point in the same direction. But full-blown Idealism, in the sense which involves a denial of the independent existence of matter, is always associated with the name of Bishop Berkeley.
I can best make my meaning plain to you by quoting a passage or two from his Principles of Human Knowledge, in which he extends to the primary qualities of matter the analysis which Locke had already applied to the secondary.
'But, though it were possible that solid, figured, moveable substances may exist without the mind, corresponding to the ideas we have of bodies, yet how is it possible for us to know this? Either we must know it by Sense or by Reason.—As for our senses, by them we have the knowledge only of our sensations, ideas, or those things that are immediately perceived by sense, call them what you will; but they do not inform us that things exist {13} without the mind, or unperceived, like to those which are perceived. This the Materialists themselves acknowledge.—It remains therefore that if we have any knowledge at all of external things, it must be by Reason inferring their existence from what is immediately perceived by sense. But what reason can induce us to believe the existence of bodies without the mind, from what we perceive, since the very patrons of Matter themselves do not pretend there is any necessary connexion betwixt them and our ideas? I say it is granted on all hands—and what happens in dreams, frenzies, and the like, puts it beyond dispute—that it is possible we might be affected with all the ideas we have now, though there were no bodies existing without resembling them. Hence, it is evident the supposition of external bodies is not necessary for the producing our ideas; since it is granted they are produced sometimes, and might possibly be produced always in the same order we see them in at present, without their concurrence.
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'In short, if there were external bodies, it is impossible we should ever come to know it; and if there were not, we might have the very same reasons to think there were that we have now. Suppose—what no one can deny possible—an intelligence without the help of external bodies, to be affected with the same train of sensations or ideas that you are, imprinted in the same order and with like vividness in his mind. I ask whether that intelligence hath not all the reason to believe the existence of corporeal substances, represented by his ideas, and exciting them in his mind, that you can possibly have for believing the same thing? Of this there can be no {14} question—which one consideration were enough to make any reasonable person suspect the strength of whatever arguments he may think himself to have, for the existence of bodies without the mind.'[4]
Do you say that in that case the tables and chairs must be supposed to disappear the moment we all leave the room? It is true that we do commonly think of the tables and chairs as remaining, even when there is no one there to see or touch them. But that only means, Berkeley explains, that if we or any one else were to come back into the room, we should perceive them. Moreover, even in thinking of them as things which might be perceived under certain conditions, they have entered our minds and so proclaimed their ideal or mind-implying character. To prove that things exist without the mind we should have to conceive of things as unconceived or unthought of. And that is a feat which no one has ever yet succeeded in accomplishing.
Here is Berkeley's own answer to the objection:
'But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park, or books existing in a closet, and nobody by to perceive them. I answer, you may so, there is no difficulty in it; but what is all this, I beseech you, more than framing in your mind certain ideas which you call books and trees, and {15} at the same time omitting to frame the idea of any one that may perceive them? But do not you yourself perceive or think of them all the while? This therefore is nothing to the purpose: it only shews you have the power of imagining or forming ideas in your mind; but it does not shew that you can conceive it possible the objects of your thought may exist without the mind. To make out this, it is necessary that you conceive them existing unconceived or unthought of, which is a manifest repugnancy. When we do our utmost to conceive the existence of external bodies, we are all the while only contemplating our own ideas. But the mind, taking no notice of itself, is deluded to think it can and does conceive bodies existing unthought of or without the mind, though at the same time they are apprehended by, or exist in, itself. A little attention will discover to any one the truth and evidence of what is here said, and make it unnecessary to insist on any other proofs against the existence of material substance.'[5]
Berkeley no doubt did not adequately appreciate the importance of the distinction between mere sensations and mental relations. In the paragraph which I have read to you he tends to explain space away into mere subjective feelings: in this respect and in many others he has been corrected by Kant and the post-Kantian Idealists. Doubtless we cannot analyse away our conception of space or of substance into mere feelings. But relations imply mind no less than sensations. Things are no mere {16} bundles of sensations; we do think of them as objects or substances possessing attributes. Indeed to call them (with Berkeley), 'bundles of sensations' implies that the bundle is as important an element in thinghood as the sensations themselves. The bundle implies what Kant would call the intellectual 'categories' of Substance, Quantity, Quality, and the like. We do think objects: but an object is still an object of thought. We can attach no intelligible meaning to the term 'object' which does not imply a subject.
If there is nothing in matter, as we know it, which does not obviously imply mind, if the very idea of matter is unintelligible apart from mind, it is clear that matter can never have existed without mind.