That night he wrote in his diary, "Challenge a remaining taboo." It was that simple. He had always wanted to understand genius, and now he had the formula. Freud, living in an age that prized its own seeming rationality, had found one of the remaining taboos and dared to think beyond it: he discovered infant sexuality and the unconscious, among other things. Galileo had gone beyond the taboo "Thou shalt not question Aristotle." Every great discovery had been the breaking of a taboo.