Comment on ``Consistent Sets Yield Contrary Inferences in Quantum Theory''

TL;DR

This paper clarifies that in consistent histories quantum theory, mutually exclusive propositions within different consistent families cannot be logically compared, reaffirming the theory's internal consistency and alignment with quantum predictions.

Contribution

It emphasizes that propositions from different consistent families are not contrary in the logical sense, clarifying a misconception about the theory's logical structure.

Findings

Consistent histories quantum theory is logically consistent.

Propositions from different consistent families cannot be directly compared.

The theory aligns with experimental results and quantum predictions.

Abstract

In a recent paper Kent has pointed out that in consistent histories quantum theory it is possible, given initial and final states, to construct two different consistent families of histories, in each of which there is a proposition that can be inferred with probability one, and such that the projectors representing these two propositions are mutually orthogonal. In this note we stress that, according to the rules of consistent history reasoning two such propositions are not contrary in the usual logical sense namely, that one can infer that if one is true then the other is false, and both could be false. No single consistent family contains both propositions, together with the initial and final states, and hence the propositions cannot be logically compared. Consistent histories quantum theory is logically consistent, consistent with experiment as far as is known, consistent with the usual quantum predictions for measurements, and applicable to the most general physical systems. It may not be the only theory with these properties, but in our opinion, it is the most promising among present possibilities.