History of Western Philosophy - Bertrand Russell [97]
Aristotle's metaphysics, roughly speaking, may be described as Plato diluted by common sense. He is difficult because Plato and common sense do not mix easily. When one tries to understand him, one thinks part of the time that he is expressing the ordinary views of a person innocent of philosophy, and the rest of the time that he is setting forth Platonism with a new vocabulary. It does not do to lay too much stress on any single passage, because there is liable to be a correction or modification of it in some later passage. On the whole, the easiest way to understand both his theory of universals and his theory of matter and form is to set forth first the common-sense doctrine which is half of his view, and then to consider the Platonic modifications to which he subjects it.
Up to a certain point, the theory of universals is quite simple. In language, there are proper names, and there are adjectives. The proper names apply to 'things' or 'persons', each of which is the only thing or person to which the name in question applies. The sun, the moon, France, Napoleon, are unique; there are not a number of instances of things to which these names apply. On the other hand, words like 'cat', 'dog', 'man' apply to many different things. The problem of universals is concerned with the meanings of such words, and also of adjectives, such as 'white', 'hard', 'round', and so on. He says:3 'By the term "universal" I mean that which is of such a nature as to be predicated of many subjects, by "individual" that which is not thus predicated.'
What is signified by a proper name is a 'substance', while what is signified by an adjective or class-name, such as 'human' or 'man', is called a 'universal'. A substance is a 'this', but a universal is a 'such'—it indicates the sort of thing, not the actual particular thing. A universal is not a substance, because it is not a 'this'. (Plato's heavenly bed would be a 'this' to those who could perceive it; this is a matter as to which Aristotle disagrees with Plato.) 'It seems impossible,' Aristotle says, 'that any universal term should be the name of a substance. For … the substance of each thing is that which is peculiar to it, which does not belong to anything else; but the universal is common, since that is called universal which is such as to belong to more than one thing.' The gist of the matter, so far, is that a universal cannot exist by itself, but only in particular things.
Superficially, Aristotle's doctrine is plain enough. Suppose I say 'there is such a thing as the game of football,' most people would regard the remark as a truism. But if I were to infer that football could exist without football-players, I should be rightly held to be talking nonsense. Similarly, it would be held, there is such a thing as parenthood, but only because there are parents; there is such a thing as sweetness, but only because there are sweet things; and there is redness, but only because there are red things. And this dependence is thought to be not reciprocal: the men who play football would still exist even if they never played football; things which are usually sweet may turn sour; and my face, which is usually red, may turn pale without ceasing to be my face. In this way we are led to conclude that what is meant by an adjective is dependent for its being on what is meant by a proper name, but not vice versa. This is, I think, what Aristotle means. His doctrine on this point, as on many others, is a common-sense prejudice pedantically expressed.
But it is not easy