Nesse addresses the problem of integrating psychoanalytic thinking with recent advances in evolutionary biological theory. Because of the expenditure of energy necessary to maintain repression, he finds it "implausible that repression exists merely to control impulses or to simplify mental life." He elaborates on the theses of the biologists, Trivers and Alexander, that by concealing motives from the self, repression makes it easier to conceal motives from others, which confers an adaptive advantage. He contends that deception often serves to maintain secure relationships, and that defenses can be understood as specialized methods of deceiving others. He describes how each of several specific defenses may contribute to the ultimate goal of deceiving others in order to establish and maintain sexual relationships, and therefore confer genetic selective advantage.