As the wheel turns: a centennial reflection on Freud's Three Essays on the Theory of Sexuality.

Freud's theories of psychosexual development, while highly original, were anchored in the explosion of scientific studies of sex in the nineteenth century. Most of these studies were based on masturbation, homosexuality, and deviance, with little attention given to normal sexuality. Around the turn of the century, the narrow interest in pathological sexuality and sexual physiology gradually gave way to a broader interest in normal sexuality. It was in the context of these expanding studies of sexuality that Freud proposed the first psychological view of sexuality, a theory that defined sex as being at the interface between soma and psyche. Libido theory, which Freud developed, is a theory of drives and conflicts. For Freud, libido was the major force in personality development, and he posited sexual conflicts as the heart of neuroses, sexual fixations as the essence of perversions. This article traces the way Freud's libido theory has served as one of the mainsprings in the development of psychoanalytic theory. It also addresses the major revisions that have taken place in libido theory, with a focus primarily on object relations theory, and the impact of culture on the way sex and sexual mores are parsed.