if so, in what sense, is a metaphysical question, which need not be raised in connection with the use of language. The only point about universals that needs to be raised at this stage is that the correct use of general words is no evidence that a man can think about universals. It has often been supposed that, because we can use a word like "man" correctly, we must be capable of a corresponding "abstract idea" of man, but this is quite a mistake. Some reactions are appropriate to one man, some to another, but all have certain elements in common. If the word "man" produces in us the reactions which are common but no others, we may be said to understand the word "man". In learning geometry, one acquires the habit of avoiding special interpretations of such a word as "triangle". We know that, when we have a proposition about triangles in general, we must not think specially of a right-angled triangle or any one kind of triangle. This is essentially the process of learning to associate with the word what is associated with all triangles; when we have learnt this, we understand the word "triangle". Consequently there is no need to suppose that we ever apprehend universals, although we use general words correctly.
Hitherto we have spoken of single words, and among these we have considered only those that can naturally be employed singly. A child uses single words of a certain kind before constructing sentences; but some words pre- suppose sentences. No one would use the word "paternity" until after using such sentences as "John is the father of James"; no one would use the word "causality" until after using such sentences as "the fire makes me warm". Sentences introduce new considerations, and are not quite so easily explained on behaviourist lines. Philosophy, however, imperatively demands an understanding of sentences, and we must therefore consider them.
As we found earlier, all infants outside Patagonia begin with single words, and only achieve sentences later. But they differ enormously in the speed with which they advance from the one to the other. My own two children adopted
