In a talk given at Zürich in the late 1940s, Hermann Weyl discussed Ferdinand Gonseth’s dialectical epistemology and considered it as being restricted too strictly to aspects of historical change. His experiences with post-kantian dialectical philosophy, in particular Johann Gottlieb Fichte’s derivation of the concept of space and matter, had been a stronger dialectical background for his own 1918 studies in purely infinitesimal geometry and the early geometrically unified field theory of matter (extending the Mie-Hilbert program). Although now Weyl distantiated himself from the speculative features of his youthful philosophizing and in particular from his earlier enthusiasum for Fichte, he again had deep doubts as to the cultural foundations of modern mathematical sciences and its role in material culture of high modernity. For Weyl, philosophical «reflection» was a cultural necessity : he now turned towards Karl Jaspers’ and Martin Heidegger’s existentialism to find deeper grounds, similar to his turn towards Fichte’s philosophy after World War I. The discussion in the late 1940s can be read as a kind of post-World-War-II «Nachtrag» to Weyl’s more widely known philosophical comments on mathematics and the natural sciences published in the middle of the 1920s.