certain animals, and destroying others; and when we ask ourselves, from the standpoint of an outside observer, what is the end achieved by all these activities, we find that it can be summed up in one very simple formula: to transform as much as possible of the matter on the earth’s surface into human bodies. Domestication of animals, agriculture, commerce, industrialism have been stages in this process. When we compare the human population of the globe with that of other large animals and also with that of former times, we see that “chemical imperialism” has been, in fact, the main end to which human intelligence has been devoted. Perhaps intelligence is reaching the point where it can conceive worthier ends, concerned with the quality rather than the quantity of human life. But as yet such intelligence is confined to minorities, and does not control the great movements of human affairs. Whether this will ever be changed I do not venture to predict. And in pursuing the simple purpose of maximising the amount of human life, we have at any rate the consolation of feeling at one with the whole movement of living things from their earliest origin on this planet. CHAPTER III THE PROCESS OF LEARNING IN ANIMALS AND INFANTS In the present chapter I wish to consider the processes by which, and the laws according to which, an animal’s original repertoire of reflexes is changed into a quite different set of habits as a result of events that happen to it. A dog learns to follow his master in preference to anyone else; a horse learns to know his own stall in the stable; a cow learns to come to the cow-shed at milking time. All these are acquired habits, not reflexes; they depend upon the circumstances of the animals concerned, not merely upon the congenital characteristics of the species. When I speak of an animal “learning” something, I shall include all cases of acquired habits, whether or not they are useful to the animal. I have known horses in Italy “learn” to drink wine, which I cannot believe to have been a desirable habit. A dog may “learn” to fly at a man who has ill-treated it, and may do so with such regularity and ferocity as to lead to its being killed. I do not use learning in any sense involving praise, but merely to denote modification of behaviour as the result of experience.