Badcock, and Nesse and Lloyd, have argued that there are important points of agreement between Freud's theory of the mind and a theory of mind suggested by adaptive reasoning. Buller, on the other hand, draws attention to the need to avoid confusing an adaptive rationale with an unconscious motivation. The present paper attempts to indicate what role adaptive reasoning might have to play in justifying psychoanalytic claims. First, it is argued that psychoanalytic claims cannot be justified by the clinical experience of psychoanalysts alone. It is urged that, to avoid interpretative proliferation, it is necessary to base interpretation on some theory which is external to psychoanalysis. Next, Buller's reservations about using adaptive reasoning to justify claims about a personal unconscious, are summarized. Then an argument for the existence of a personal unconscious, is offered, based on experimental evidence from Gur and Sackeim. Then it is argued that adaptive reasoning, though it cannot itself provide evidence for the existence of any psychological mechanism, can valuably guide the search for such evidence. It is argued that such an approach has borne fruit, both in biology generally and specifically in psychology. Finally, it is argued that psychoanalysis is important enough to justify such a research project.