During the first ten years of his career in psychological medicine, Sigmund Freud espoused a theory of unconsciousness which predated his own. As Rosemarie Sand describes in The Unconscious without Freud, he would evolve this theory over the course of his career and eventually apply it to his own psychological practice. Once Freud's hypothesis of unconscious mental functioning was published, the same professionals who had valued the traditional concept turned against what they considered to be a catastrophic, logically indefensible revision. The scientific investigation of unconscious...