Bohr on Bell: A Proposed Reading of Bohr and its Implications for Bell’s Theorem

Abstract

Despite some helpful recent studies, I believe that philosophers of physics have yet to understand fully Bohr’s reply to Einstein, Podolsky, and Rosen’s (EPR’s) argument that quantum mechanics is incomplete. The first part of this paper is an attempt to make some progress towards full understanding, by first noting a few crucial points about EPR’s argument, then spelling out Bohr’s reply. Bohr’s reply inhabits a logical space that can be described in terms of the counterfactual reasoning needed by EPR to establish their conclusion. Bohr had reasonable physical grounds for adopting a position that occupies this logical space. The second part of the paper then examines the extent to which Bohr can adopt a similar position in response to the case considered by Bohm—the case of two particles correlated not in position and momentum, but in spin. While the same logical space exists in this case—the logic of Bohm’s version of the argument is identical to that of EPR’s version—it is less clear that Bohr’s reply remains physically well-grounded.