This paper addresses the questions raised by the evidence presented that many cardinal psycho-analytic notions bear a strong resemblance to the ideas of Schopenhauer and Nietzsche. In the process, the author considers not only that the 19th century Zeitgeist, given its preoccupation with the unconscious, created a fertile ground for the birth of psychoanalysis, but the influence on the Weltanschauung of Freud, Schopenhauer and Nietzsche of their common German cultural heritage, their shared admiration for Shakespeare and love of Hellenic culture, (...) and the meteoric rise of science. Although influence may not be sharply separated from confluence, the parallels between Freud's concepts and those of Schopenhauer and Nietzsche are too specific to be coincidental. And yet, Freud vehemently denied ever having read these philosophers’ works until “very late in life”. It is suggested that an unconscious sense of guilt may have induced that denial.This study adopts a cross-sectional approach that juxtaposes Freud's cardinal concepts with the ideas of Schopenhauer and Nietzsche. Its tripartite structure has the advantage of observing similarities and differences not only between Freud and the two philosophers, but also between Nietzsche and Schopenhauer. The focal concepts include: the unconscious; ego, id and superego; libido; drives; repression; sublimation; dreams; catharsis; free association; primary and secondary process thinking; Oedipus complex; repetition compulsion; the pleasure principle; mourning and melancholia; a criminal from a sense of guilt; and the death instinct. (shrink)