  The spectacular successes of quantum physics have made it a commonplace to
assert that we live in a quantum world. This idea seems to imply a kind of
"quantum fundamentalism" according to which everything in the universe (if not
the universe as a whole) is fundamentally of a quantum nature and ultimately
describable in quantum-mechanical terms. Bohr's conception of quantum mechanics
has traditionally been seen as opposed to such a view, not least because of his
insistence on the necessity of the concepts of classical physics in the account
of quantum phenomena. Recently, however, a consensus seems to be emerging among
careful commentators on Bohr to the effect that he, after all, did subscribe to
some version of quantum fundamentalism. Against this consensus, and by
re-examining the historical record, I will defend a variant of the traditional
reading of Bohr in which (1) the answer to what an object is (quantum or
classical) depends on the experimental context; and (2) in principle, any
physical system can be treated quantum-mechanically but not all systems can be
treated that way at the same time.

History and Philosophy of Physics;Quantum Physics