This paper draws attention to a confusion in the psychoanalytic literature concerning the concept ‘psychic determinism’. The work of two authors are cited in which the concept is identified as foundational to psychoanalysis, in the one case as ‘fundamental hypothesis’ (Brenner) and in the other as an ‘underlying presupposition’ or assumption (Brakel). I argue that both these claims are based on a confusion stemming from a conflation of the concept Freud had in mind, and a philosophical doctrine going by the same name but meaning something different. I show that the philosophical doctrine has no place in psychoanalysis at all, and that Freud's concept does not have a foundational role. Finally I suggest some ideas that may explain how this confusion may have arisen.