Talk this week – David Yates

Wednesday 23 November 2016 at Geneva – David Yates (University of Lisbon): Spacetime functionalism and empirical coherence

Abstract: Quantum gravity research seems to suggest that spacetime is not fundamental, but this in turn threatens the existence of the “local beables”—meters, pointers, dials—we observe to gain evidence for fundamental physical theories. How can a physical theory be justified if there are no local beables in its ontology? Spacetime functionalism promises a conservative truthmaking theory for empirical truths, which explains how it is that statements such as ‘the pointer moved to position 5 on the dial’ come out true even though the fundamental ontology is not straightforwardly spatiotemporal. There are several different functionalist positions available—depending on which concepts we take to be functional, and what roles we take to define them—and it isn’t always clear how they interact. Spacetime functionalists (Knox) argue that the concept of a spacetime is the concept of whatever it is that occupies a certain set of roles within physical theory. Because the concept of spacetime is topic-neutral, even if the fundamental quantum ontology turns out to be very unlike the spacetime of the manifest image, we should not conclude on that basis that there is no spacetime for local beables to occupy. The occupant of the spacetime roles may or may not be fundamental, and it may or may not be recognisable spatiotemporal. This theory shows us how a necessary condition on the truth of empirical statements is consistent with a non-spatiotemporal fundamental ontology, but stops short of a truthmaking theory for such statements. Spacetime occupant-functionalism (Wallace, Ney) and spacetime property-functionalism (Chalmers) offer topic-neutral analyses of our concepts of ordinary objects and spatiotemporal properties respectively, and jointly offer the promise of such a theory. In this talk I argue that property-functionalism fails, and that there is therefore no topic-neutral analysis of our ordinary empirical claims about local beables. I argue further that at least some spatiotemporal property concepts fail to have topic-neutral analyses because they are directly referring concepts that are at least partially transparent with respect to their referents. It follows, I suggest, that either the fundamental quantum ontology is spatiotemporal after all, or local beables inhabit a grounded spacetime. I suggest the latter, and conclude by considering whether a grounded spacetime might also be fundamental, hence ontologically emergent.  In terms of technical difficulty, this talk rates 1/5 1

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