The founder of psychoanalysis — the theory that unconscious mental processes shape behavior, that childhood experience forms adult personality, and that repressed desires drive neurotic symptoms — whose ideas transformed how educated people in the 20th century understood themselves, regardless of whether those ideas were scientifically valid.
Freud's theories are not supported by the scientific evidence assembled since his death. His specific mechanisms — the id, ego, and superego; the Oedipus complex; penis envy; the libido as a hydraulic system — have not been confirmed by neuroscience or by controlled clinical research. And yet Freud remains one of the most consequential thinkers of the 20th century. Understanding why a set of largely falsified ideas shaped the century requires understanding what problems those ideas addressed, what needs they met, and why the framework survived its scientific refutation.