Prior to her extended stay in Leipzig and her 1935 essay on the foundations of quantum mechanics, Grete Hermann had written a manuscript on "Determinism and Quantum Mechanics", which she had sent to some of the main quantum physicists at the time but had since disappeared. This manuscript was rediscovered by us in the Dirac Archive and appears in translation as Chap.  14 of this volume. In this chapter we give a first analysis of this fascinating manuscript, in which Hermann criticises known arguments for the incompatibility of quantum mechanics and determinism, including the theorem in von Neumann's 1932 book, and sketches what a completion of quantum mechanics might have to look like.