From a methodological point of view, both Newton and Einstein, and later Dirac, unreservedly supported the principle of mathematical simplicity in the discovery of new physical laws of nature. They were joined by Poincaré and Weyl. Eduard Prugovecki states that quantum gravity has forced the consideration of some fundamental epistemological questions, which can be identified in philosophy with the mind-body problem and the problem of free will. These questions influenced the epistemology of quantum mechanics in the form of von Neumann’s “psycho-physical parallelism” and Wigner’s subsequent analysis of the thesis that the “collapse of the wave packet” occurs in the mind of the “observer”.