The problem of discontinuity in the work of the German architect Erich Mendelsohn (1887-1953) is redefined through a closer look at the biographical context and a critique of the established historiography. Mendelsohn's Jewish status, artistic background, and education are discussed as conditions in the transition to a more professional attitude. The role of the avant garde is considered for its spiritual and artistic influences, and Mendelsohn's sketches are analysed as a uniquely artistic method of composition. The Einsteinturm, the climax of his Expressionist period, is the point of departure for his subsequent buildings. The influence of the Neue Sachlichkeit and the importance of Richard Neutra are shown to be instrumental in Mendelsohn's metamorphosis. Historians have either embraced Mendelsohn and his early Expressionism, or rejected him completely, rather than trying to comprehend his transition to professionalism and his compromise with urban circumstances.