Psychic determinism is a basic tenet of psychoanalysis. It is commonly defined as an application of the causality principle to psychic occurrences. Causality, however, is no longer accepted as a basic postulate in the advanced physical sciences. This dilemma is recognized by the psychoanalysts, who nevertheless would prefer to retain a deterministic point of view.Psychic determinism may be defined without reference to causality, by using the mathematical concept of a function. Whether or not the psyche is a deterministic system, in the mathematical sense, cannot be decided in the present state of our knowledge.Regardless of the definition chosen, psychic determinism is best regarded as a working hypothesis, which cannot be established on a priori grounds.Abstract Teaser