Such being the nature and scope of psychology, the ques tion that next presents itself is: what is the use of psychology? What possible service can it render us to study psychology The answer is not difficult. Our entire waking life is devoted to activities which realize certain aims, to the forming of resolutions or the carrying out of purposes. At least half probably far more than half with most people — of our aims, resolutions, and purposes involve in a greater or less degree reference also to the activities of other people, involve co-operating with other people or opposing them, protecting them or protecting ourselves against them, advising or educating, checking or punishing them. Our whole active life, therefore, may be said to be devoted to the controlling and modifying of our behaviour by ourselves or others, or the controlling and modifying of the behaviour of other people by us, and we study behaviour in order through the better understanding of it to be able better to modify and control it.