In this short note, the extraordinary similarity between the worlds of Freud and of the Ratman is underlined. Aspects relating to four areas are taken into account. First is their family background: the same Eastern European origin of a Jewish family, which was also of similar composition. Second, we see the same entanglement of death and sex in Freud and in Lanzer, and a strong ambivalence towards the father. Third, the mother was dominant in Freud's family of origin, as she was in that of Lanzer, in important matters. Finally, the worlds of Freud and Lanzer had much ground in common, and Freud understood the obsessional neurosis of Lanzer from within. A short conclusion is added, stipulating that the closeness of both men and the strong bond between them enabled Freud to understand Lanzer and to make him quit his stuck position.