“It seems to me that we must make a distinction between what is "objective" and what is "measurable" in discussing the question of physical reality, according to quantum mechanics.”

—  Roger Penrose , book The Emperor's New Mind

Source: The Emperor's New Mind (1989), Ch. 6, Quantum Magic and Quantum Mastery, p. 269.
Context: It seems to me that we must make a distinction between what is "objective" and what is "measurable" in discussing the question of physical reality, according to quantum mechanics. The state-vector of a system is, indeed, not measurable, in the sense that one cannot ascertain, by experiments performed on the system, precisely (up to proportionality) what the state is; but the state-vector does seem to be (again up to proportionality) a completely objective property of the system, being completely characterized by the results it must give to experiments that one might perform.

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Roger Penrose 15
English mathematical physicist, recreational mathematician … 1931

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