But habits of stupidity are not confined to particular regions of thought. Becoming almost as incapable of mental change as a beetle, a man may undergo an arrest of mental development which differs from that of the idiot only because it occurs later in life, is less complete, and is acquired, not innate. In his ordinary surroundings he appears a normal person; but placed among people of more open mind, his brute-like inability to learn suggests sharply the resemblance to the feeble-minded child. Let us sum up. Man has conquered the earth because he is pre-eminently the educable, the adaptive animal. His educability--indeed, his whole thinking capacity--depends on his memory. He has few instincts, a fact which increases his mental ductility; but one of the most important of his instincts is imitativeness, which impels him to copy not only such obvious things as the speech of his predecessors, but their mental attitudes as well. In this way not only the actual knowledge and beliefs but also the habits of thought of one generation are handed on to the next. Apart from a few instincts which are more active in the child than in the adult, and two or three others whose appearance is deferred till later life, the whole mental difference between the child and the adult lies in the fact that the former has a great memory in the sense that it is very capable of storing experience, whereas the latter has a great memory in the sense that it has already stored much experience. As parent to child, so one racial generation hands on its acquirements to the next, but with greater certainty; for the parent is not the only influence in the life of the child, who imitates many other people, sometimes more closely than the parent; whereas, since few individuals travel during youth, the young are seldom influenced by others than by members of their own race. Except in times of great change, therefore, racial generations resemble one another even more closely than parents and children. Like individuals, races differ in their mental characteristics. The English have one set of characters, the Japanese another, and the Russians a third. The problem of the extent to which these characters are inborn or acquired is very important to the student of history. Accordingly as we believe they are the one or the other we are driven to accept one or other of two very different readings of the past. [Sidenote: Influences in a Child’s Life]