Attentively reading Ferenczi's works and his scientific and “auto-analytic” correspondence with Sigmund Freud, the author insists on the important contribution of the Hungarian psychoanalyst concerning the contemporary matter of the complex relations between biology and psychoanalysis: Ferenczi considered in fact that the unconscious was an occult phenomenon allowing an intersubjective thought-transference and was desperately searching for the material evidence of traumatic scenes and life events, reducing the psychical reality to body-writing. Freud was contrarily and prudently convinced that the unconscious processes were dependent on the materiality of the registration of the signifier, constituted by corporeal traces, but which had to be understood more in relation to language and speech phenomena than the reality of fallacious sensations.