Abstracts

Geneva has a plan

Christian Wüthrich (University of Geneva)

Spacetime functionalism is best equipped to avoid the problem of empirical incoherence in quantum gravity. While work in the philosophy of mind has proven useful in developing a suitable form of spacetime functionalism, there are various ways in which the templates from the philosophy of mind are inadequate to the task. First, the direction of “explanation” runs parallel to the direction of functional reduction in quantum gravity, whereas the two directions are opposed in the Canberra plan of functional reduction of mental states. Second, in quantum gravity, unlike in the case of mind, we should expect “near-realization” or mere approximation to emergent spacetime to take central stage. These two failures of the Canberra plan in the philosophy of mind suggest its being replaced in quantum gravity with a new plan.

Quantum gravity ‘is’ as spacetime does?

Nick Huggett (University of Illinois, Chicago)

“Psychophysical and Theoretical Identifications” (Lewis, 1972) proposed a functionalist identity theory of mind, explicitly understood as a particular instance of scientific identification (he gives the example of light and electromagnetic radiation). The idea (and essay) are multidimensional, and different philosophers have foregrounded different aspects for use or criticism: reduction, ontology, or ontological respectability, for instance. It also relies on standard logical tools, including a set-theoretic semantics – a ‘language-first’ understanding of science, which has recently been challenged by Wallace (2022), developing Saunders’ suggestion of a ‘math-first’ interpretation of theoretical claims. Such a shift threatens to explode the traditional ontological concerns of functionalism, by doing away with the ‘things’ that compose sets.

In this talk I want to stress another aspect of Lewis’s functionalism, the semantic: how do we secure reference for theoretical terms, which places his (1972) in the context of his (1970). The question is especially pressing in the case of a theory without spacetime, such as versions of quantum gravity, because our talk of the concrete seems so rooted in spatiotemporal properties. In Huggett and Wüthrich (2021) we suggest Lewis’ functional approach to defining theoretical terms solves the problem: the stuff of quantum gravity is to be understood as ‘that which plays the spacetime roles’. I will explain this proposal in relation to other functionalist projects, and argument that Lewis’ general scheme for defining theoretical terms in this way survives math-first interpretation.

References

Huggett, N., Wüthrich, C. (2021). Out of Nowhere: Introduction: The emergence of spacetime. arXiv:2101.06955.

Lewis, D. K. (1970). General semantics. Synthese 22(1-2):18-67.

Lewis, D. K. (1972). Psychophysical and Theoretical Identifications. Australasian Journal of Philosophy 50(3): 249-258.

Wallace, D. (2022). Stating structural realism: mathematics-first approaches to physics and metaphysics. Philosophical Perspectives 36(1): 345-378.

Beyond Spacetime Functionalism, A Defense of Spacetime Composition

Baptiste Le Bihan (University of Geneva)

The possible emergence or non-fundamentality of spacetime has perplexed physicists and philosophers on numerous fronts. It has been suggested that this emergence can be understood through the lens of functional realization, as advocated by proponents of spacetime functionalism. In this talk, I aim to argue briefly that spacetime functionalism is better conceptualized as spacetime eliminativism. I will defend the realist perspective that regards spacetime as a composition of non-spatiotemporal, perhaps causal, building blocks.

Spacetime emergence in Quantum Gravity: What role for functionalism?

Emilia Margoni (University of Florence, Geneva, Pisa) & Daniele Oriti (Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-University, Munich)

Recently, Lam and Wüthrich (2018) have suggested that spacetime functionalism – the view according to which spacetime is functionally realized by an underlying, more fundamental ontology – is the path to explore to properly account for the recovery of spacetime. Here we put this conceptual strategy to the test by focusing on a specific approach to Quantum Gravity (QG), namely the Group Field Theory (GFT). The structure of the presentation is the following. After introducing the functionalist strategy in the context of QG, we will provide a sketchy account of the GFT approach and evaluate the tenability of the functionalist strategy within this context.

References

Lam, V. and Wüthrich, C. (2018). Spacetime is as spacetime does. Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 64: 39-51.