Elise Crull

Grete Hermann’s Lost Manuscript on Quantum Mechanics

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.

Hermann and the Relative Context of Observation

Prior analyses of Grete Hermann’s 1935 essay on the philosophical foundations of quantum mechanics have taken her central aim to be the recovery of an appropriately Kantian notion of causality from this new indeterministic physics. I argue that if one instead reads this essay as primarily an investigation into the meaning and implications of the relative nature of quantum mechanics—not only for physics, but also for fields as different as ethics—certain dimensions of her work appear with greater clarity. Among these are her particular Kantian interpretation of Bohr’s complementarity and correspondence principles , her unique understanding of the quantum-classical divide , the failure of Kant’s a priori categories of space, time and causality to apply literally—even for obtaining classical natural knowledge, and the splitting of truth.