Time reversal invariance and ontology

TL;DR

This paper argues that classical electrodynamics and non-relativistic quantum mechanics are time reversal invariant when considering an appropriate ontological framework, countering recent philosophical challenges.

Contribution

It demonstrates that the debate over time reversal invariance can be resolved by ontological underdetermination, aligning these theories with the standard view.

Findings

Theories are time reversal invariant with suitable ontology

Ontology choice affects interpretation of invariance

Counteracts recent philosophical criticisms

Abstract

Albert and Callender have challenged the received view that theories like classical electrodynamics and non-relativistic quantum mechanics are time reversal invariant. They claim that time reversal should correspond to the mere reversal of the temporal order of the instantaneous states, without any accompanying change of the instantaneous state as in the standard view. As such, Albert and Callender claim, these theories are not time reversal invariant. The view of Albert and Callender has been much criticized, with many philosophers arguing that time reversal may correspond to more than the reversal of the temporal order. In this paper, we will not so much engage with that aspect of the debate, but rather deflate the disagreement by exploiting the ontological underdetermination. Namely, it will be argued that with a suitable choice of ontology, these theories are in fact time reversal invariant in the sense of Albert and Callender, in agreement with the standard view.