 Cassirer’s assimilation of Einstein’s general theory of relativity marked a watershed in the development of his thought. It not only gave him an opportunity, as we have just seen, to reinterpret the Kantian theory of the a priori conditions of objective experience (especially as involving space and time) in terms of Cassirer’s own version of the genetic conception of knowledge, but it also provided him with an impetus to generalize and extend the original Marburg view in such a way that modern mathematical scientific knowledge in general is now seen as just one possible “symbolic form” among other equally valid and legitimate such forms. Indeed, [Cassirer 1921] first officially announces the project of a general “philosophy of symbolic forms,” conceived, in this context, as a philosophical extension of “the general postulate of relativity.” Just as, according to the general postulate of relativity, all possible reference frames and coordinate systems are viewed as equally good representations of physical reality, and, as a totality, are together interrelated and embraced by precisely this postulate, similarly the totality of “symbolic forms” – aesthetic, ethical, religious, scientific – are here envisioned by Cassirer as standing in a closely analogous relationship. So it is no wonder that, subsequent to taking up the professorship at Hamburg in 1919, Cassirer devotes the rest of his career to this new philosophy of symbolic forms. (Cassirer’s work in the philosophy of natural science in particular also continued, notably in [Cassirer 1936].)