Thus the Proof Runs in a Circle: Grete Hermann and Her Refutation of No Hidden Variables Arguments

Summary

In 1935, Grete Hermann published an extensive article about the philosophical foundations of quantum theory in an almost unknown philosophical journal that is still worth reading today. This article became particularly famous because it contained a refusal of a theorem of John von Neumann according to which any extension of quantum theory by hidden variables in order to explain the apparent indeterminism is impossible. Until today some of the questions concerning this refusal are still under debate: To which extent was John von Neumann aware of how restrictive his assumptions were? To which extent is Grete Hermann’s claim justified that von Neumann’s proof is circular? And in particular: to which extent was Grete Hermann really convinced that such an extension of quantum theory is not necessary in order to save the causality principle, which is one of the conclusions of her article?

In his talk, Prof. Thomas Filk will summarize Grete Hermann's main arguments as well as give a brief account of the history related to two of her articles: the (by now) famous one from 1935, and a remarkable manuscript from 1933, which was long-lost for many years and reappeared only a few years ago.