Speakable in Quantum Mechanics

TL;DR

This paper develops a quantum logic framework that emphasizes the language of what can be said about nature, minimizing assumptions of realism, and compares it to classical mechanics and realist interpretations.

Contribution

It introduces a novel quantum logic based on Bohr's motto, avoiding realism, and demonstrates its relation to classical mechanics and interpretations.

Findings

Quantum logic is a special case of the derived logic for classical mechanics.

The logic framework aligns with Bohr's view on the language of physics.

Implications for realist interpretations are discussed.

Abstract

At the 1927 Como conference Bohr spoke the now famous words "It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature." However, if the Copenhagen interpretation really holds on to this motto, why then is there this feeling of conflict when comparing it with realist interpretations? Surely what one can say about nature should in a certain sense be interpretation independent. In this paper I take Bohr's motto seriously and develop a quantum logic that avoids assuming any form of realism as much as possible. To illustrate the non-triviality of this motto a similar result is first derived for classical mechanics. It turns out that the logic for classical mechanics is a special case of the derived quantum logic. Finally, some hints are provided in how these logics are to be used in practical situations and I discuss how some realist interpretations relate to these logics.