Stephen Hawking Quote
Although I'm regarded as a dangerous radical by particle physicists for proposing that there may be loss of quantum coherence, I'm definitely a conservative compared to Roger. I take the positivist viewpoint that a physical theory is just a mathematical model and that it is meaningless to ask whether it corresponds to reality. All that one can ask is that its predictions should be in agreement with observation. I think Roger [Penrose] is a Platonist at heart but he must answer for himself.
The Nature of Space and Time (2000) by Stephen W. Hawking and Roger Penrose, Ch. 1 : Classical Theory, p. 3.