Locke may be regarded as the founder of empiricism, which is the doctrine that all our knowledge (with the possible exception of logic and mathematics) is derived from experience. Accordingly the first book of the Essay is concerned in arguing, as against Plato, Descartes, and the scholastics, that there are no innate ideas or principles. In the
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* Essay Concerning Human Understanding, Book IV, Ch. XVI, Sec. 4.
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second book he sets to work to show, in detail, how experience gives rise to various kinds of ideas. Having rejected innate ideas, he says:
“Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas; how comes it to be furnished? Whence comes it by that vast store, which the busy and boundless fancy of man has painted on it with an almost endless variety? Whence has it all the materials of reason and knowledge? To this I answer in one word, from experience: in that all our knowledge is founded, and from that it ultimately derives itself” (Book II, Ch. I, Sec. 2).
Our ideas are derived from two sources, (a) sensation, and (b) perception of the operation of our own mind, which may be called “internal sense.” Since we can only think by means of ideas, and since all ideas come from experience, it is evident that none of our knowledge can antedate experience.
Perception, he says, is “the first step and degree towards knowledge, and the inlet of all the materials of it.” This may seem, to a modern, almost a truism, since it has become part of educated common sense, at least in English-speaking countries. But in his day the mind was supposed to know all sorts of things a priori, and the complete dependence of knowledge upon perception, which he proclaimed, was a new and revolutionary doctrine. Plato, in the Theaetetus, had set to work to refute the identification of knowledge with perception, and from his time onwards almost all philosophers, down to and including Descartes and Leibniz, had taught that much of our most valuable knowledge is not derived from experience. Locke’s thorough-going empiricism was therefore a bold innovation.
The third book of the Essay deals with words, and is concerned, in the main, to show that what metaphysicians present as knowledge about the world is purely verbal. Chapter III, “Of General Terms,” takes up an extreme nominalist position on the subject of universals. All things that exist are particulars, but we can frame general ideas, such as “man,” that are applicable to many particulars, and to these general ideas we can give names. Their generality consists solely in the fact that they are, or may be, applicable to a variety of particular things; in their own being, as ideas in our minds, they are just as particular as everything else that exists.
Chapter VI of Book III, “Of the Names of Substances,” is concerned to refute the scholastic doctrine of essence. Things may have
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a real essence, which will consist of their physical constitution, but this is in the main unknown to us, and is not the “essence” of which scholastics speak. Essence, as we can know it, is purely verbal; it consists merely in the definition of a general term. To argue, for instance, as to whether the essence of body is only extension, or is extension plus solidity, is to argue about words: we may define the word “body” either way, and no harm can result so long as we adhere to our definition. Distinct species are not a fact of nature, but of language; they are “distinct complex ideas with distinct names annexed to them.” There are, it is true, differing things in nature, but the differences proceed by continuous gradations: “the boundaries of the species, whereby men sort them, are made by men.” He proceeds to give instances of monstrosities, concerning which it was doubtful whether they were men or not. This point of view was not generally accepted until Darwin persuaded men to adopt the theory of evolution by gradual changes. Only those who have allowed themselves to be afflicted by the scholastics will realize how much metaphysical lumber it sweeps away.
Empiricism and idealism alike are faced with a problem to which, so far, philosophy has found no satisfactory solution. This is the problem of showing how we have knowledge of other things than ourself and the operations of our own mind. Locke considers this problem, but what he says is very obviously unsatisfactory. In one place * we are told: “Since the mind, in all its thoughts and reasonings, hath no other immediate object but its own ideas, which it alone does or can contemplate, it is evident that our knowledge is only conversant about them.” And again: “Knowledge is the perception of the agreement or disagreement of two ideas.” From this it would seem to follow immediately that we cannot know of the existence of other people, or of the physical world, for these, if they exist, are not merely ideas in any mind. Each one of us, accordingly, must, so far as knowledge is concerned, be shut up in himself, and cut off from all contact with the outer world.
This, however, is a paradox, and Locke will have nothing to do with paradoxes. Accordingly, in another chapter, he sets forth a different theory, quite inconsistent with the earlier one. We have, he
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* Op. cit., Book IV, Ch. I.
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tells us, three kinds of knowledge of real existence. Our knowledge of our own existence is intuitive, our knowledge of God’s existence is demonstrative, and our knowledge of things present to sense is sensitive (Book IV, Ch. III).
In the next chapter, he becomes more or less aware of the inconsistency. He suggests that some one might say: “If knowledge consists in agreement of ideas, the enthusiast and the sober man are on a level.” He replies: “Not so where ideas agree with things.” He proceeds to argue that all simple ideas must agree with things, since “the mind, as has been showed, can by no means make to itself” any simple ideas, these being all “the product of things operating on the mind in a natural way.” And as regards complex ideas of substances, “all our complex ideas of them must be such, and such only, as are made up of such simple ones as have been discovered to coexist in nature.” Again, we can have no knowledge except (1) by intuition, (2) by reason, examining the agreement or disagreement of two ideas, (3) “by sensation, perceiving the existence of particular things” (Book IV, Ch. III, Sec. 2).
In all this, Locke assumes it known that certain mental occurrences, which he calls sensations, have causes outside themselves, and that these causes, at least to some extent and in certain respects, resemble the sensations which are their effects. But how, consistently with the principles of empiricism, is this to be known? We experience the sensations, but not their causes; our experience will be exactly the same if our sensations arise spontaneously. The belief that sensations have causes, and still more the belief that they resemble their causes, is one which, if maintained, must be maintained on grounds wholly independent of experience. The view that “knowledge is the perception of the agreement or disagreement of two ideas” is the one that Locke is entitled to, and his escape from the paradoxes that it entails is effected by means of an inconsistency so gross that only his resolute adherence to common sense could have made him blind to it.
This difficulty has troubled empiricism down to the present day. Hume got rid of it by dropping the assumption that sensations have external causes, but even he retained this assumption whenever he forgot his own principles, which was very often. His fundamental maxim, “no idea without an antecedent impression,” which he takes over from Locke, is only plausible so long as we think of impressions
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as having outside causes, which the very word “impression” irresistibly suggests. And at the moments when Hume achieves some degree of consistency he is wildly paradoxical.
No one has yet succeeded in inventing a philosophy at once credible and self-consistent. Locke aimed at credibility, and achieved it at the expense of consistency. Most of the great philosophers have done the opposite. A philosophy which is not self-consistent cannot be wholly true, but a philosophy which is self-consistent can very well be wholly false. The most fruitful philosophies have contained glaring inconsistencies, but for that very reason have been partially true. There is no reason to suppose that a self-consistent system contains more truth than one which, like Locke’s, is obviously more or less wrong.
Locke’s ethical doctrines are interesting, partly on their own account, partly as an anticipation of Bentham. When I speak of his ethical doctrines, I do not mean his moral disposition as a practical man, but his general theories as to how men act and how they should act. Like Bentham, Locke was a man filled with kindly feeling, who yet held that everybody (including himself) must always be moved, in action, solely by desire for his own happiness or pleasure. A few quotations will make this
