I want to know the answer to the following question:
Von Neumann's abstract treatment allowed him to work on what foundational issue?
All the background I'm provided with is that "Von Neumann's abstract treatment permitted him also to confront the foundational issue of determinism versus non-determinism, and in the book he presented a proof that the statistical results of quantum mechanics could not possibly be averages of an underlying set of determined "hidden variables," as in classical statistical mechanics.". Is that enough to answer the question?
Answer: yes