S ndor Ferenczi's mutual analysis with Elizabeth Severn-the patient known as R.N. in the Clinical Diary-is one of the most controversial and consequential episodes in the history of psychoanalysis. In his latest groundbreaking work, Peter L. Rudnytsky draws on a trove of archival sources to provide a definitive scholarly account of this experiment, which constitutes a paradigm for relational psychoanalysis, as Freud's self-analysis does...