Past exam of the mathematics course of the University of Cambridge / 2012 / iii / Paper 66 / 3 / a

The EPR criterion of reality proposes that a quantity has an element of physical reality when its value can be predicted with certainty without disturbing the system. It is a sufficient criterion, not a claim that every uncertain prediction is unreal. In the original locality argument, measuring one member of a separated correlated pair allows such a prediction for the other, whose physical condition is assumed unaffected by the remote choice.