The Fate of Causal Structure under Time Reversal

TL;DR

This paper explores how causal structures are affected by time reversal, arguing that traditional notions of causality do not straightforwardly apply to time-reversed worlds due to their instability and contingent features.

Contribution

It challenges the assumption that causal relations simply reverse under time reversal, proposing instead that causal concepts may not be applicable or reliable in time-reversed scenarios.

Findings

Time-reversed dynamical evolutions are unstable under intervention.

Causal concepts depend on contingent structural features of the actual world.

Traditional causal relations do not straightforwardly apply to time-reversed worlds.

Abstract

What happens to the causal structure of a world when time is reversed? At first glance it seems there are two possible answers: the causal relations are reversed, or they are not. I argue that neither of these answers is correct: we should either deny that time-reversed worlds have causal relations at all, or deny that causal concepts developed in the actual world are reliable guides to the causal structure of time-reversed worlds. The first option is motivated by the instability under intervention of time-reversed dynamical evolutions. The second option is motivated by a recognition of how contingent structural features of the actual world shape, and license the application of, our causal concepts and reasoning strategies.