The contributions of Jung to classical psychoanalytic theory are enumerated and described, the author pointing to the cross-fertilization of ideas between Jung and Freud. Jung's association experiments were felt to support the cornerstone of psychoanalysis: his most important contribution the pointing out to Freud the latter's failure to separate sharply neurotic and psychotic phenomona in the Schreber case, which ostensibly led Freud to revise his libido theory.