Eduard Heimann earned his doctorate under Alfred Weber. In the Weimar period, he was best known for his studies of the welfare state and his close collaboration with Paul Tillich. He retained his ties with Tillich during his American exile, when he taught social policy at the New School. Mannheim probably knew him in Heidelberg, as well as in Christian Socialist circle around Tillich in Frankfurt. The exchange with Heimann is Mannheim’s only contribution to a set of letters that Tillich and his associates circulated among themselves, evidently in the hope of generating a periodical out of this traffic. Other participants included Mannheim’s close friend, Adolph Loewe, Alexander Rüstow, and Arnold Wolfers. Extant letters cover topics in macrosocial theory notably the questions posed by Oppenheimer about the role of force in primal social organization, as well as the planning problems addressed in the Mannheim—Heimann correspondence. Although these letters date from Mannheim’s English period, they focus specifically on unfinished business from the Weimar years. The short German core of the book that later appeared in English much expanded was addressed specifically to his German peers in exile.