On the meaning of EPR\u2019s Reality Criterion

Márton Gömöri,Gábor Hofer-Szabó

doi:10.1007/s11229-021-03382-3

Abstract

This essay has two main claims about EPR’s Reality Criterion. First, we claim that the application of the Reality Criterion makes an essential difference between the EPR argument and Einstein’s later arguments against quantum mechanics. We show that while the EPR argument, making use of the Reality Criterion, does derive that certain interpretations of quantum mechanics are incomplete, Einstein’s later arguments, making no use of the Reality Criterion, do not prove incompleteness, but rather point to the inadequacy of the Copenhagen interpretation. We take this fact as an indication that the Reality Criterion is a crucial, indispensable component of the incompleteness argument(s). The second claim is more substantive. We argue that the Reality Criterion is a special case of the Common Cause Principle. Finally, we relate this proposal to Tim Maudlin’s recent assertion that the Reality Criterion is an analytic truth.

Highlights

Is how EPR famously formulate in their 1935 paper on the incompleteness of quantum mechanics (QM) what has come to be known as the Reality Criterion (RC): If, without in any way disturbing a system, we can predict with certainty the value of a physical quantity, there exists an element of physical reality corresponding to this physical quantity. (Einstein et al 1935, p. 777) SynthesePurely looking at its wording, it is striking how general and deeply philosophical this criterion is
We show that while the EPR argument, making use of the Reality Criterion, does derive that certain interpretations of quantum mechanics are incomplete, Einstein’s later arguments, making no use of the Reality Criterion, do not prove incompleteness, but rather point to the inadequacy of the Copenhagen interpretation
Is how EPR famously formulate in their 1935 paper on the incompleteness of quantum mechanics (QM) what has come to be known as the Reality Criterion (RC): If, without in any way disturbing a system, we can predict with certainty the value of a physical quantity, there exists an element of physical reality corresponding to this physical quantity. (Einstein et al 1935, p. 777)

Summary

Introduction

Is how EPR famously formulate in their 1935 paper on the incompleteness of quantum mechanics (QM) what has come to be known as the Reality Criterion (RC): If, without in any way disturbing a system, we can predict with certainty (i.e. with probability equal to unity) the value of a physical quantity, there exists an element of physical reality corresponding to this physical quantity. (Einstein et al 1935, p. 777). Looking at its wording, it is striking how general and deeply philosophical this criterion is It is a principle of apparent epistemological character that provides a way, as EPR put it, of “recognizing a physical reality” Our analysis is meant to be a logical reconstruction of EPR’s and Einstein’s arguments, providing a unitary conceptual framework–in terms of causally explaining correlations–to think about these arguments, and to relate them to Bell’s treatment and contemporary discussion To set out such a reconstruction, we will need to sharpen, and to an extent revise, some of our historically loaded terminology–such as what we mean by the Copenhagen interpretation or completeness/incompleteness.

Two interpretations of the quantum formalism

The EPR argument implies the existence of new elements of reality

The Reality Criterion is a special case of the Common Cause Principle

The Reality Criterion is not analytic

Discussion