The Metaphysics of D-CTCs: On the Underlying Assumptions of Deutsch's Quantum Solution to the Paradoxes of Time Travel

TL;DR

This paper critically examines Deutsch's quantum model for time travel paradoxes, arguing it depends on a metaphysical assumption of parallel worlds beyond standard quantum theory, thus challenging its claim as a purely quantum solution.

Contribution

The paper reveals that Deutsch's D-CTC model relies on a metaphysical assumption of parallel worlds, which extends beyond standard quantum theory and affects its interpretation of time travel paradoxes.

Findings

Deutsch's model depends on a multiverse of parallel worlds

Standard Everett interpretation does not support multiple identical worlds

Deutsch's approach involves structures beyond quantum theory

Abstract

I argue that Deutsch's model for the behavior of systems traveling around closed timelike curves (CTCs) relies implicitly on a substantive metaphysical assumption. Deutsch is employing a version of quantum theory with a significantly supplemented ontology of parallel existent worlds, which differ in kind from the many worlds of the Everett interpretation. Standard Everett does not support the existence of multiple identical copies of the world, which the D-CTC model requires. This has been obscured because he often refers to the branching structure of Everett as a "multiverse", and describes quantum interference by reference to parallel interacting definite worlds. But he admits that this is only an approximation to Everett. The D-CTC model, however, relies crucially on the existence of a multiverse of parallel interacting worlds. Since his model is supplemented by structures that go significantly beyond quantum theory, and play an ineliminable role in its predictions and explanations, it does not represent a quantum solution to the paradoxes of time travel.