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only in the percipient. Without the eye, there would be no colours; without the ear, no sounds, and so on. For Locke’s view as to secondary qualities there are good grounds–jaundice, blue spectacles, etc. But Berkeley pointed out that the same arguments apply to primary qualities. Ever since Berkeley, Locke’s dualism on this point has been philosophically out of date. Nevertheless, it dominated practical physics until the rise of quantum theory in our own day. Not only was it assumed, explicitly or tacitly, by physicists, but it proved fruitful as a source of many very important discoveries. The theory that the physical world consists only of matter in motion was the basis of the accepted theories of sound, heat, light, and electricity. Pragmatically, the theory was useful, however mistaken it may have been theoretically. This is typical of Locke’s doctrines.
Locke’s philosophy, as it appears in the Essay, has throughout certain merits and certain demerits. Both alike were useful: the demerits are such only from a theoretical standpoint. He is always sensible, and always willing to sacrifice logic rather than become paradoxical. He enunciates general principles which, as the reader can hardly fail to perceive, are capable of leading to strange consequences; but whenever the strange consequences seem about to appear, Locke blandly refrains from drawing them. To a logician this is irritating; to a practical man, it is a proof of sound judgement. Since the world is what it is, it is clear that valid reasoning from sound principles cannot lead to error; but a principle may be so nearly true as to deserve theoretical respect, and yet may lead to practical consequences which we feel to be absurd. There is therefore a justification for common sense in philosophy, but only as showing that our theoretical principles cannot be quite correct so long as their consequences are condemned by an appeal to common sense which we feel to be irresistible. The theorist may retort that common sense is no more infallible than logic. But this retort, though made by Berkeley and Hume, would have been wholly foreign to Locke’s intellectual temper.
A characteristic of Locke, which descended from him to the whole Liberal movement, is lack of dogmatism. Some few certainties he takes over from his predecessors: our own existence, the existence of God, and the truth of mathematics. But wherever his doctrines differ from those of his forerunners, they are to the effect that truth is hard to ascertain, and that a rational man will hold his opinions with
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some measure of doubt. This temper of mind is obviously connected with religious toleration, with the success of parliamentary democracy, with laissez-faire, and with the whole system of liberal maxims. Although he is a deeply religious man, a devout believer in Christianity who accepts revelation as a source of knowledge, he nevertheless hedges round professed revelations with rational safeguards. On one occasion he says: “The bare testimony of revelation is the highest certainty,” but on another he says: “Revelation must be judged by reason.” Thus in the end reason remains supreme.
His chapter “Of Enthusiasm” is instructive in this connection. “Enthusiasm” had not then the same meaning as it has now; it meant the belief in a personal revelation to a religious leader or to his followers. It was a characteristic of the sects that had been defeated at the Restoration. When there is a multiplicity of such personal revelations, all inconsistent with each other, truth, or what passes as such, becomes purely personal, and loses its social character. Love of truth, which Locke considers essential, is a very different thing from love of some particular doctrine which is proclaimed as the truth. One unerring mark of love of truth, he says, is “not entertaining any proposition with greater assurance than the proofs it is built upon will warrant.” Forwardness to dictate, he says, shows failure of love of truth. “Enthusiasm, laying by reason, would set up revelation without it; whereby in effect it takes away both reason and revelation, and substitutes in the room of it the ungrounded fancies of a man’s own brain.” Men who suffer from melancholy or conceit are likely to have “persuasions of immediate intercourse with the Deity.” Hence odd actions and opinions acquire Divine sanction, which flatters “men’s laziness, ignorance, and vanity.” He concludes the chapter with the maxim already quoted, that “revelation must be judged of by reason.”
What Locke means by “reason” is to be gathered from his whole book. There is, it is true, a chapter called “Of Reason,” but this is mainly concerned to prove that reason does not consist of syllogistic reasoning, and is summed up in the sentence: “God has not been so sparing to men to make them barely two-legged creatures, and left it to Aristotle to make them rational.” Reason, as Locke uses the term, consists of two parts: first, an inquiry as to what things we know with certainty; second, an investigation of propositions which it is wise to accept in practice, although they have only probability and not
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certainty in their favour. “The grounds of probability,” he says, “are two: conformity with our own experience, or the testimony of other’s experience.” The King of Siam, he remarks, ceased to believe what Europeans told him when they mentioned ice.
In his chapter “Of Degrees of Assent” he says that the degree of assent we give to any proposition should depend upon the grounds of probability in its favour. After pointing out that we must often act upon probabilities that fall short of certainty, he says that the right use of this consideration “is mutual charity and forbearance. Since therefore it is unavoidable to the greatest part of men, if not all, to have several opinions, without certain and indubitable proofs of their truth; and it carries too great an imputation of ignorance, lightness, or folly, for men to quit and renounce their former tenets presently upon the offer of an argument which they cannot immediately answer and show the insufficiency of; it would, methinks, become all men to maintain peace and the common offices of humanity and friendship in the diversity of opinions, since we cannot reasonably expect that any one should readily and obsequiously quit his own opinion, and embrace ours with a blind resignation to an authority which the understanding of man acknowledges not. For, however it may often mistake, it can own no other guide but reason, nor blindly submit to the will and dictates of another. If he you would bring over to your sentiments be one that examines before he assents, you must give him leave at his leisure to go over the account again, and, recalling what is out of his mind, examine the particulars, to see on which side the advantage lies; and if he will not think over arguments of weight enough to engage him anew in so much pains, it is but what we do often ourselves in the like case; and we should take it amiss if others should prescribe to us what points we should study: and if he be one who wishes to take his opinions upon trust, how can we imagine that he should renounce those tenets which time and custom have so settled in his mind that he thinks them self-evident, and of an unquestionable certainty; or which he takes to be impressions he has received from God himself, or from men sent by him? How can we expect, I say, that opinions thus settled should be given up to the arguments or authority of a stranger or adversary? especially if there be any suspicion of interest or design, as there never fails to be where men find themselves ill-treated. We should do well to commiserate our
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mutual ignorance, and endeavour to remove it in all the gentle and fair ways of information, and not instantly treat others ill as obstinate and perverse because they will not renounce their own and receive our opinions, or at least those we would force upon them, when it is more than probable that we are no less obstinate in not embracing some of theirs. For where is the man that has uncontestable evidence of the truth of all that he holds, or of the falsehood of all he condemns; or can say, that he has examined to the bottom all his own or other men’s opinions? The necessity of believing without knowledge, nay, often upon very slight grounds, in this fleeting state of action and blindness we are in, should make us more busy and careful to inform ourselves than to restrain others. . . . There is reason to think, that if men were better instructed
themselves, they would be less imposing on others.” *
I have dealt hitherto only with the latest chapters of the Essay, where Locke is drawing the moral from his earlier theoretical investigation of the nature and limitations of human knowledge. It is time now to examine what he has to say on this more purely philosophical subject.
Locke is, as a rule, contemptuous of metaphysics. A propos of some speculation of Leibniz’s, he writes to a friend: “You and I have had enough of this kind of fiddling.” The conception of substance, which was dominant in the metaphysics of his time, he considers vague and not useful, but he does not venture to reject it wholly.
