Rudolf Carnap’s formative years as a philosopher were his time in Jena where he studied mathematics, physics, and philosophy, among others, with Gottlob Frege, the neo-Kantian Bruno Bauch, and Herman Nohl, a pupil of Wilhelm Dilthey.2 Whereas both the influence of Frege and of the neo-Kantians is quite well known,3 the importance of the Dilthey school for Carnap’s intellectual development was recently highlighted by scholars, such as Gottfried Gabriel and Hans-Joachim Dahms.4 Although Carnap himself was interested mainly in the problems (...) of logic and the philosophy of the natural sciences, the community in which he worked until he went to Vienna in 1926 was neither a community of neo-Kantian philosophers nor of logicians or philosophers of the natural sciences but a community of members of the Dilthey school that were interested in history of philosophy ,5 pedagogic ,6 aesthetics ,7 and sociology .8 Carnap and his friends were all members of the so-called Seracircle, a group of young people that met frequently in Jena and, between 1919 and 1926, also in Carnap’s home in Buchenbach near Freiburg.9 The first version of the Aufbau was written in close connection with this group of young people that were interested in a reform of the whole society, including arts, politics, sciences, and everyday life. In Carnap’s Werkstatt in Buchenbach, the Aufbau and at least two more manifestos of a more or less philosophical nature were written: Franz Roh’s “Nach-Expressionismus” and Wilhelm Flitner’s “Laienbildung.”10 Given these historical facts, we must conclude that the Aufbau is the product of an intellectual enterprise that developed in close connection with the Dilthey school, but in which Frege and the neo-Kantians seem to have played only a small role. (shrink)