 Turning to the historical influences on the Vienna Circle itself, the scholarship of recent decades has unearthed a much greater variety than was previously recognized. Scientifically, the strongest influences belonged to the physicists Helmholtz, Mach and Boltzmann, the mathematicians Hilbert and Klein and the logicians Frege and Russell; amongst contemporaries, Einstein was revered above all others. The Circle’s philosophical influences extend far beyond that of the British empiricists (especially Hume), to include the French conventionalists Henri Poincaré, Pierre Duhem and Abel Rey, American pragmatists like James and, in German-language philosophy, the Neo-Kantianism of both the Heidelberg and the Marburg variety, even the early phenomenology of Husserl as well as the Austrian tradition of Bolzano’s logic and the Brentano school. (See Frank 1949a for the influence of the French conventionalists; for the importance of Neo-Kantianism for Carnap, see Friedman 1987, 1992, Sauer 1989, Richardson 1998, Mormann 2007; for Neo-Kantianism in Schlick, see Coffa 1991, Ch. 9 and Gower 2000; for the significance of Husserl for Carnap, see Sarkar 2004, Ryckman 2007, Carus 2016, Damböck 2018; for the influence of and sympathies for pragmatism see Frank 1949a and Uebel 2016; the Bolzano-Brentano connection is explored in Haller 1986.) It is against this very wide background of influences that the seminal force must be assessed that their contemporary Wittgenstein exerted. The literature on the relation between Wittgenstein and the Vienna Circle is vast but very often suffers from an over-simplified conception of the latter. (See Stern 2007 for an attempt by a Wittgenstein scholar to redress the balance.) Needless to say, different wings of the Circle show these influences to different degrees. German Neo-Kantianism was important for Schlick and particularly so for Carnap, whereas the Austrian naturalist-pragmatist influences were particularly strong on Hahn, Frank and Neurath. Frege was of great importance for Carnap, less so for Hahn who looked to Russell. Most importantly, by no means all members of the Vienna Circle sought to emulate Wittgenstein—thus the division between the faction around Schlick and the left wing (see Uebel 2017).