The notion of ‘‘measurement’’ plays a fundamental role in
conventional formulations of quantum mechanics. Indeed,
quantum mechanics is often presented as merely an algorithm
that takes you from one measurement -‘‘state preparation’’
involves selecting a particular output channel from a
measurement apparatus - to another. John Bell railed eloquently
against this. Why should the scope of physics be
restricted to the artificial contrivances we are forced to resort
to in our efforts to probe the world? Why should a fundamental
theory have to take its meaning from a notion of
‘‘measurement’’ external to the theory itself? Should not the
meaning of ‘‘measurement’’ emerge from the theory, rather
than the other way around? Should not physics be able to
make statements about the unmeasured, unprepared world?
To restrict quantum mechanics to be exclusively
about piddling laboratory operations is to betray
the great enterprise. A serious formulation will
not exclude the big world outside of the laboratory.
N. David Mermin
From What is quantum mechanics trying to tell us?