"From about my seventeenth year, my reading of science, especially biology, zoology and astronomy, became regular and assiduous. I read every book by Darwin, Haeckel, Huxley, Romanes, Spencer and Proctor that I could lay my hands on. With great avidity, I also read Huxley’s famous controversy with Wace, following the arguments on each side with breathless interest and becoming a convinced agnostic in the process. But the two authors that probably exerted the greatest influence on me in my early twenties were Schopenhauer and Schiller. The former enlightened me enormously on psychology, and I still regard him as the greatest European psychologist who appeared between Montaigne and Freud. Indeed, there is much in his work that anticipates Freud’s discoveries, a fact to which I have more than once called attention, and Nietzsche owed him many a profound observation, the source of which, however, is rarely acknowledged."