This study examines the relationship between psychoanalysis and neuroscience. It argues that the Project, the traditional starting-point for such an examination, provides few substantial links between Freud's neurological and psychoanalytic careers. The neurological model that the Project endorsed was not derived from Freud's formal neurological education, as has so often been assumed. It was based, instead, on the Jacksonian model that he developed in 'On aphasia' in 1891.

'On aphasia' appears to be the real 'missing link' between Freud's neurological and psychological years. The fundamental principles that it endorsed provided the framework within which psychoanalysis developed.