 Bohr’s response to EPR begins, as do many of his treatments of the conceptual issues raised by the quantum theory, with a discussion of limitations on the simultaneous determination of position and momentum. As usual, these are drawn from an analysis of the possibilities of measurement if one uses an apparatus consisting of a diaphragm connected to a rigid frame. Bohr emphasizes that the question is to what extent can we trace the interaction between the particle being measured and the measuring instrument. (See Beller 1999, Chapter 7 for a detailed analysis and discussion of the “two voices” contained in Bohr’s account. See too Bacciagaluppi 2015.) Following the summary of EPR, Bohr (1935a, p. 700) then focuses on the Criterion of Reality which, he says, “contains an ambiguity as regards the meaning of the expression ‘without in any way disturbing a system’.” Bohr agrees that in the indirect measurement of Niels’ system achieved when one makes a measurement of Albert’s system “there is no question of a mechanical disturbance” of Niels’ system. Still, Bohr claims that a measurement on Albert’s system does involve “an influence on the very conditions which define the possible types of predictions regarding the future behavior of [Niels’] system.” The meaning of this claim is not at all clear. Indeed, in revisiting EPR fifteen years later, Bohr would comment, 