I am now convinced that theoretical physics is actually philosophy. It has revolutionized fundamental concepts, e. g., abut space and time (relativity), about causality (quantum theory), and about substance and matter (atomistics). It has taught us new methods of thinking (complimentarity), which are applicable far beyond physics.

Statement of 1963, as quoted in Schrodinger : Life and Thought (1992) by Walter J. Moore, p. 1