In this chapter, the author sets out the defence mechanisms of introjection and projection for her major consideration and incorporates findings of British psychoanalysts concerning ways in which these processes contribute to the formation of the ego. The individual responds to the reality of his experience by interpreting it, or rather, 'misinterpreting' it. The pioneer work of Melanie Klein has led in particular to a close study of these problems in the British Psycho-Analytical Society and in the author's view has directly or indirectly influenced most of the work of its members in recent years. In Inhibitions, Symptoms and Anxiety, in considering the relations between instinct and anxiety, Freud has throughout dealt solely with the demands of Eros, but has not discussed those of the other great primary instinct and their relations to anxiety. The anxiety-situations which arise from the interplay of aggression and libido form the starting-point of much of the work of English analysts.