Page "Bell's theorem" Paragraph 2

In his groundbreaking 1964 paper, " On the Einstein Podolsky Rosen paradox ", physicist John Stewart Bell presented an analogy ( based on spin measurements on pairs of entangled electrons ) to EPR's hypothetical paradox.

Using their reasoning, he said, a choice of measurement setting here should not affect the outcome of a measurement there ( and vice versa ).

After providing a mathematical formulation of locality and realism based on this, he showed specific cases where this would be inconsistent with the predictions of QM.