 The EPR text is concerned, in the first instance, with the logical connections between two assertions. One asserts that quantum mechanics is incomplete. The other asserts that incompatible quantities (those whose operators do not commute, like the x-coordinate of position and linear momentum in direction x) cannot have simultaneous “reality” (i.e., simultaneously real values). The authors assert the disjunction of these as a first premise (later to be justified): one or another of these must hold. It follows that if quantum mechanics were complete (so that the first assertion failed) then the second one would hold; i.e., incompatible quantities cannot have real values simultaneously. They take as a second premise (also to be justified) that if quantum mechanics were complete, then incompatible quantities (in particular coordinates of position and momentum) could indeed have simultaneous, real values. They conclude that quantum mechanics is incomplete. The conclusion certainly follows since otherwise (if the theory were complete) one would have a contradiction over simultaneous values. Nevertheless the argument is highly abstract and formulaic and even at this point in its development one can readily appreciate Einstein’s disappointment.