When the actual world is not even possible

TL;DR

This paper explores the implications of quantum gravity theories where space and time are not fundamental, challenging existing metaphysical and modal analyses such as David Lewis's possible worlds framework.

Contribution

It critically examines the metaphysical consequences of non-fundamental spacetime, highlighting issues for Lewis's modal realism in the context of quantum gravity.

Findings

Non-fundamentality of spacetime challenges Lewis's possible worlds.

Empirical coherence requires recovering spacetime at the fundamental level.

Lewis's theory may render our actual world impossible.

Abstract

Approaches to quantum gravity often involve the disappearance of space and time at the fundamental level. The metaphysical consequences of this disappearance are profound, as is illustrated with David Lewis's analysis of modality. As Lewis's possible worlds are unified by the spatiotemporal relations among their parts, the non-fundamentality of spacetime---if borne out---suggests a serious problem for his analysis: his pluriverse, for all its ontological abundance, does not contain our world. Although the mere existence---as opposed to the fundamentality---of spacetime must be recovered from the fundamental structure in order to guarantee the empirical coherence of the non-spatiotemporal fundamental theory, it does not suffice to salvage Lewis's theory of modality from the charge of rendering our actual world impossible.