language arose, nor why chimpanzees do not speak. I doubt if it is even known whether writing or speech is the older form of language. The pictures made in caves by the Cro-Magnon men may have been intended to convey a meaning, and may have been a form of writing. It is known that writing developed out of pictures, for that happened in historical times; but it is not known to what extent pictures had been used in prehistoric times as a means of giving information or commands. As for spoken language, it differs from the cries of animals in being not merely an expression of emotion. Animals have cries of fear, cries expressing pleasure in the discovery of food, and so on, and by means of these cries they influence each other's actions. But they do not appear to have any means of expressing anything except emotions, and then only emotions which they are actually feeling. There is no evidence that they possess anything analogous to narrative. We may say, therefore, without exaggeration, that language is a human prerogative, and probably the chief habit in which we are superior to the "dumb" animals.
There are three matters to be considered in beginning the study of language. First: what words are, regarded as physical occurrences; secondly, what are the circumstances that lead us to use a given word; thirdly, what are the effects of our hearing or seeing a given word. But as regards the second and third of these questions, we shall find ourselves led on from words to sentences and thus confronted with fresh problems, perhaps demanding rather the methods of Gestaltpsychologie.
Ordinary words are of four kinds: spoken, heard, written, and read. It is of course largely a matter of convention that we do not use words of other kinds. There is the deaf-and-dumb language; a Frenchman's shrug of the shoulders is a word; in fact, any kind of externally perceptible bodily movement may become a word, if social usage so ordains. But the convention which has given the supremacy to speaking is one which has a good ground, since there is no other way of producing a number of perceptibly different bodily move-
