The Problem of Generalities. Carnap and Kaufmann in Comparison (1928-1934)

Between 1928 and 1934, Rudolf Carnap and Felix Kaufmann engaged in an intense discussion on the difference between two types of generalities. Kaufmann introduces the topic, but both consider it decisive for the theory of meaning and the philosophy of mathematics. That is two of the central issues in the discussions of the Vienna Circle, one related to the confrontation with Tractatus, the other to that with Principia Mathematica. Through the difference between generalities, Kaufmann brings Husserlian theories of abstraction and concept into Vienna. For the first, and perhaps the only time, a live confrontation between phenomenology and logical neo-empiricism takes place. After a brief exposition of state-of-the-art on generalities in contemporary literature, the paper presents in the first paragraph the Kaufmannian definition of the two generalities and its application to the philosophy of mathematics, in the second, the Husserlian presuppositions of the distinction in the third the first phase of the debate between Kaufmann and Carnap (1928-1931) and in the fourth the second phase (1928-1934). The main result of the confrontation is the definition of thing language and the discussion on the extent of its extension, decisive arguments for the liberalisation of the empirical criterion of significance and thus for the fate of 20th-century empiricism.