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LOCKE'S THEORY OF KNOWLEDGE

John Locke (1632–1704) is the apostle of the Revolution of 1688, the most moderate and the most successful of all revolutions. Its aims were modest, but they were exactly achieved, and no subsequent revolution has hitherto been found necessary in England. Locke faithfully embodies its spirit, and most of his works appeared within a few years of 1688. His chief work in theoretical philosophy, the Essay Concerning Human Understanding, was finished in 1687 and published in 1690. His First Letter on Tolerationwas originally published in Latin in 1689, in Holland, to which country Locke had found it prudent to withdraw in 1683. Two further letters on Toleration were published in 1690 and 1692. His two Treatises on Government were licensed for printing in 1689, and published soon afterwards. His book on Education was published in 1693. Although his life was long, all his influential writings are confined to the few years from 1687 to 1693. Successful revolutions are stimulating to those who believe in them.

Locke's father was a Puritan, who fought on the side of Parliament. In the time of Cromwell, when Locke was at Oxford, the university was still scholastic in its philosophy; Locke disliked both scholasticism and the fanaticism of the Independents. He was much influenced by Descartes. He became a physician, and his patron was Lord Shaftesbury, Dryden's 'Achitophel'. When Shaftesbury fell in 1683, Locke fled with him to Holland, and remained there until the Revolution. After the Revolution, except for a few years during which he was employed at the Board of Trade, his life was devoted to literary work and to numerous controversies arising out of his books.

The years before the Revolution of 1688, when Locke could not, without grave risk, take any part, theoretical or practical, in English politics, were spent by him in composing his Essay Concerning Human Understanding. This is his most important book, and the one upon which his fame most securely rests; but his influence on the philosophy of politics was so great and so lasting that he must be treated as the founder of philosophical liberalism as much as of empiricism in theory of knowledge.

Locke is the most fortunate of all philosophers. He completed his work in theoretical philosophy just at the moment when the government of his country fell into the hands of men who shared his political opinions. Both in practice and in theory, the views which he advocated were held, for many years to come, by the most vigorous and influential politicians and philosophers. His political doctrines, with the developments due to Montesquieu, are embedded in the American Constitution, and are to be seen at work whenever there is a dispute between President and Congress. The British Constitution was based upon his doctrines until about fifty years ago, and so was that which the French adopted in 1871.

His influence in eighteenth-century France, which was immense, was primarily due to Voltaire, who as a young man spent some time in England, and interpreted English ideas to his compatriots in the Lettres philosophiques. The philosophes and the moderate reformers followed him; the extreme revolutionaries followed Rousseau. His French followers, rightly or wrongly believed in an intimate connection between his theory of knowledge and his politics.

In England this connection is less evident. Of his two most eminent followers, Berkeley was politically unimportant, and Hume was a Tory who set forth his reactionary views in his History of England. But after the time of Kant, when German idealism began to influence English thought, there came to be again a connection between philosophy and politics: in the main, the philosophers who followed the Germans were Conservative, while the Benthamites, who were Radical, were in the tradition of Locke. The correlation, however, is not invariable; T. H. Green, for example, was a Liberal but an idealist.

Not only Locke's valid opinions, but even his errors, were useful in practice. Take, for example, his doctrine as to primary and secondary qualities. The primary qualities are defined as those that are inseparable from body, and are enumerated as solidity, extension, figure, motion or rest, and number. The secondary qualities are all the rest: colours, sounds, smells, etc. The primary qualities, he maintains, are actually in bodies; the secondary qualities, on the contrary, are 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 a sound judgment. 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 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 certainty in their favour. 'The grounds of probability,' he says, 'are two: conformity with our own experience, or the testimony of others' 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 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.'1

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. Apropos 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. He allows the validity of metaphysical arguments for the existence of God, but he does not dwell on them, and seems somewhat uncomfortable about them. Whenever he is expressing new ideas, and

not merely repeating what is traditional, he thinks in terms of concrete detail rather than of large abstractions. His philosophy is piecemeal, like scientific work, not statuesque and all of a piece, like the great Continental systems of the seventeenth century.

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 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, chap. 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 commonsense, 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 thoroughgoing 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 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 place2 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 my 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 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, chap. iii).

In the next chapter, he becomes more or less aware of the inconsistency. He suggests that someone 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, chap. 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 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 clear.

'Things are good or evil only in relation to pleasure or pain. That we call "good" which is apt to cause or increase pleasure, or diminish pain, in us.'

'What is it moves desire? I answer, happiness, and that alone.'

'Happiness, in its full extent, is the utmost pleasure we are capable of.'

'The necessity of pursuing true happiness [is] the foundation of all liberty.'

'The preference of vice to virtue [is] a manifest wrong judgment.'

'The government of our passions [is] the right improvement of liberty.'3

The last of these statements depends, it would seem, upon the doctrine of rewards and punishments in the next world. God has laid down certain moral rules; those who follow them go to heaven, and those who break them risk going to hell. The prudent pleasure-seeker will therefore be virtuous. With the decay of the belief that sin leads to hell, it has become more difficult to make a purely self-regarding argument in favour of a virtuous life. Bentham, who was a free-thinker, substituted the human lawgiver in place of God: it was the business of laws and social institutions to make a harmony between public and private interests, so that each man, in pursuing his own happiness, should be compelled to minister to the general happiness. But this is less satisfactory than the reconciliation of public and private interests effected by means of heaven and hell, both because lawgivers are not always wise or virtuous, and because human governments are not omniscient.

Locke has to admit, what is obvious, that men do not always act in the way which, on a rational calculation, is likely to secure them a maximum of pleasure. We value present pleasure more than future pleasure, and pleasure in the near future more than pleasure in the distant future. It may be said—this is not said by Locke—that the rate of interest is a quantitative measure of the general discounting of future pleasures. If the prospect of spending £1,000 a year hence were as delightful as the thought of spending it to-day, I should not need to be paid for postponing my pleasure. Locke admits that devout believers often commit sins which, by their own creed, put them in danger of hell. We all know people who put off going to the dentist longer than they would if they were engaged in the rational pursuit of pleasure. Thus, even if pleasure or the avoidance of pain be our motive, it must be added that pleasures lose their attractiveness and pains their terrors in proportion to their distance in the future.

Since it is only in the long run that, according to Locke, self-interest and the general interest coincide, it becomes important that men should be guided, as far as possible, by their long-run interests. That is to say, men should be prudent. Prudence is the one virtue which remains to be preached, for every lapse from virtue is a failure of prudence. Emphasis on prudence is characteristic of liberalism. It is connected with the rise of capitalism, for the prudent became rich while the imprudent became or remained poor. It is connected also with certain forms of Protestant piety: virtue with a view to heaven is psychologically very analogous to saving with a view to investment.

Belief in the harmony between private and public interests is characteristic of liberalism, and long survived the theological foundation that it had in Locke.

Locke states that liberty depends upon the necessity of pursuing true happiness and upon the government of our passions. This opinion he derives from his doctrine that private and public interests are identical in the long run, though not necessarily over short periods. It follows from this doctrine that, given a community of citizens who are all both pious and prudent, they will all act, given liberty, in a manner to promote the general good. There will be no need of human laws to restrain them, since divine laws will suffice. The hitherto virtuous man who is tempted to become a highwayman will say to himself: 'I might escape the human magistrate, but I could not escape punishment at the hands of the Divine Magistrate.' He will accordingly renounce his nefarious schemes, and live as virtuously as if he were sure of being caught by the police. Legal liberty, therefore, is only completely possible where both prudence and piety are universal; elsewhere, the restraints imposed by the criminal law are indispensable.

Locke states repeatedly that morality is capable of demonstration, but he does not develop this idea so fully as could be wished. The most important passage is:

"Morality capable of demonstration. The idea of a Supreme Being, infinite in power, goodness, and wisdom, whose workmanship we are, and on whom we depend; and the idea of ourselves, as understanding, rational beings, being such as are clear in us, would, I suppose, if duly considered and pursued, afford such foundations of our duty and rules of action as might place morality among the sciences capable of demonstration: wherein I doubt not, but from self-evident propositions, by necessary consequences, as incontestable as those in mathematics, the measures of right and wrong might be made out, to any one that will apply himself with the same indifferency and attention to the one as he does to the other of these sciences. The relation of other modes may certainly be perceived, as well as those of number and extension: and I cannot see why they should not also be capable of demonstration, if due methods were thought on to examine or pursue their agreement or disagreement. "Where there is no property, there is no justice", is a proposition as certain as any demonstration in Euclid: for the idea of property being a right to anything, and the idea to which the name "injustice" is given being the invasion or violation of that right, it is evident that these ideas being thus established, and these names annexed to them, I can as certainly know this proposition to be true as that a triangle has three angles equal to two right ones. Again: "No government allows absolute liberty": the idea of government being the establishment of society upon certain rules or laws, which require conformity to them; and the idea of absolute liberty being for any one to do whatever he pleases: I am as capable of being certain of the truth of this proposition as of any in the mathematics.'4"

This passage is puzzling because, at first, it seems to make moral rules dependent upon God's decrees, while in the instances that are given it is suggested that moral rules are analytic. I suppose that, in fact, Locke thought some parts of ethics analytic and others dependent upon God's decrees. Another puzzle is that the instances given do not seem to be ethical propositions at all.

There is another difficulty which one could wish to see considered. It is generally held by theologians that God's decrees are not arbitrary, but are inspired by His goodness and wisdom. This requires that there should be some concept of goodness antecedent to God's decrees, which has led Him to make just those decrees rather than any others. What this concept may be, it is impossible to discover from Locke. What he says is that a prudent man will act in such and such ways, since otherwise God will punish him; but he leaves us completely in the dark as to why punishment should be attached to certain acts rather than to their opposites.

Locke's ethical doctrines are, of course, not defensible. Apart from the fact that there is something revolting in a system which regards prudence as the only virtue, there are other, less emotional, objections to his theories.

In the first place, to say that men only desire pleasure is to put the cart before the horse. Whatever I may happen to desire, I shall feel pleasure in obtaining it; but as a rule the pleasure is due to the desire, not the desire to the pleasure. It is possible, as happens with masochists, to desire pain; in that case, there is still pleasure in the gratification of the desire, but it is mixed with its opposite. Even in Locke's own doctrine, it is not pleasure as such that is desired, since a proximate pleasure is more desired than a remote one. If morality is to be deduced from the psychology of desire, as Locke and his disciples attempt to do, there can be no reason for deprecating the discounting of distant pleasures, or for urging prudence as a moral duty. His argument, in a nutshell, is: 'We only desire pleasure. But, in fact, many men desire,

not pleasure as such, but proximate pleasure. This contradicts our doctrine that they desire pleasure as such, and is therefore wicked.' Almost all philosophers, in their ethical systems, first lay down a false doctrine, and then argue that wickedness consists in acting in a manner that proves it false, which would be impossible if the doctrine were true. Of this pattern Locke affords an example.

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