IN the summer of 1908 I had the opportunity of opening up the problem of paranoia in the course of conversation with Professor Freud, and we arrived at certain tentative ideas, which for the main part were developed by Professor Freud, while I contributed to the final shaping of the train of thought with detached suggestions and criticisms. We laid down to begin with that the mechanism of projection, as explicated by Freud in the only case of paranoia at that time analysed, is characteristic of paranois in general. We assumed further that the paranoiac mechanism stands midway between the opposite mechanisms of neurosis and of dementia praecox. The neurotic gets rid of the affects that have become disagreeable to him by means of the different forms of displacement (conversion, transference, substitution); the patient suffering from dementia praecox, on the other hand, detaches his interest