Editing Counterfactual definiteness (section)

===Consistent histories===
The [[consistent histories]] approach rejects counterfactual definiteness in yet another manner; it ascribes single but hidden values to unperformed measurements and disallows combining values of incompatible measurements (counterfactual or factual) as such combinations do not produce results that would match any obtained purely from performed compatible measurements. When a measurement is performed the hidden value is nevertheless realized as the resulting value. [[Robert Griffiths (physicist)|Robert Griffiths]] likens these to "slips of paper" placed in "opaque envelopes".<ref name="Griffiths pp. 705–733">{{cite journal | last=Griffiths | first=Robert B. | title=Quantum Locality | journal=Foundations of Physics | publisher=Springer Nature | volume=41 | issue=4 | date=2010-10-21 | issn=0015-9018 | doi=10.1007/s10701-010-9512-5 | pages=705–733| arxiv=0908.2914 | bibcode=2011FoPh...41..705G | s2cid=15312828 }}</ref> Thus Consistent Histories does not reject counterfactual results per se, it rejects them only when they are being combined with incompatible results.<ref name="Griffiths pp. 674–684">{{cite journal | last=Griffiths | first=Robert B. | title=Quantum Counterfactuals and Locality | journal=Foundations of Physics | publisher=Springer Nature | volume=42 | issue=5 | date=2012-03-16 | issn=0015-9018 | doi=10.1007/s10701-012-9637-9 | pages=674–684| arxiv=1201.0255 | bibcode=2012FoPh...42..674G | s2cid=118796867 }}</ref> Whereas in the Copenhagen interpretation or the Many Worlds interpretation, the algebraic operations to derive Bell's inequality cannot proceed due to having no value or many values where a single value is required, in Consistent Histories, they can be performed but the resulting correlation coefficients can not be equated with those that would be obtained by actual measurements (which are instead given by the rules of quantum mechanical formalism). The derivation combines incompatible results, only some of which could be factual for a given experiment and the rest counterfactual.