History of Western Philosophy - Bertrand Russell [347]
'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