Rank is the only psychoanalyst to introduce the concept of will as central to an understanding of human psychology. The function of willing and the clear uniqueness of each individual challenge the causal, deterministic thinking of Freudian psychoanalysis and thereby the predictability of behavior. Thus, for the individual “will” means “choice,” and therefore moral responsibility for one's own acts. It also means the opportunity to create the new. The very formation of the individual self as it separates and differentiates itself from the maternal matrix is a creative act—one which inevitably precipitates a certain, but normally manageable, amount of guilt because of empathic feelings for the one who has been left—originally the mother. Beyond the creation of self, the will, through its creative role, helps to allay the inevitable human fear of the final separation, namely death by producing those manifestations of civilization—art, literature, music, and science—which in their generative capacity insure immortality.