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• If what we regard as real depends on our theory, how can we make reality the basis of our philosophy? I would say that I am a realist in the sense that I think there is a universe out there waiting to be investigated and understood. I regard the solipsist position that everything is the creation of our imagination as a waste of time. No one acts on that basis. But we cannot distinguish what is real about the universe without a theory. I therefore take the view, which has been described as simple-minded or naive, that a theory of physics is just a mathematical model that we use to describe the results of observations. A theory is a good theory if it is an elegant model, if it describes a wide class of observations, and if it predicts the results of new observations. Beyond that, it makes no sense to ask if it corresponds to reality, because we do not know what reality is independent of a theory. This view of scientific theories may make me an instrumentalist or a positivist --- as I have said above, I have been called both. The person who called me a positivist went on to add that everyone knew that positivism was out of date --- another case of refutation be denegration. It may indeed be out of date in that it was yesterday's intellectual fad, but the positivist position I have outlined seems the only possible one for someone who is seeking new laws, and new ways, to describe the universe. It is no good appealing to reality because we don't have a model-independent concept of reality."
  • Stephen Hawking, Black Holes and Baby Universes and Other Essays (1993) p.44.

• One voice in the Great Conversation itself announces this modern point of view. In the closing paragraph of his Enquiry Concerning Human Understanding, David Hume writes: "When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume ... let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to flames: for it can contain nothing but sophistry and illusion." ...the positivists of our own day, would commit to burning or, what is the same, to dismissal from serious consideration... Those books... argue the case against the kind of positivism that asserts that everything except mathematics and experimental science is sophistry and illusion. ...The Great Conversation... contains both sides of the issue...
  • Robert M. (Maynard) Hutchins, Great Books: The Foundation of a Liberal Education (1954)

• [W]hatever the deity which satisfied Arnold's personal experience may have been, the religion which he gives us in Literature and Dogma and God and the Bible is neither Deism nor bare Pan-Deism, but a diluted Positivism. As an ethical system it is in theory admirable, but its positive value is in the highest degree questionable. Pascal's judgment upon the God who emerged from the philosophical investigations of Rene Descartes was that He was a God who was unnecessary. And one may with even greater truth say that the man who is able to receive and live by the religion which Arnold offers him is no longer in need of its help and stimulus. To be able to appreciate an ethical idealism a man must himself be already an ethical idealist.
  • William Harbutt Dawson, Matthew Arnold and His Relation to the Thought of Our Time (1904, republished 1977), p. 256 (1977 ed.) ISBN: 0849206480; (1904 ed.) ASIN: B0006ADKGA.