Giacomo Gianni (London School of Economics): Does Dispositionalism have (grand)daddy issues? Powers, Time Travel, and Necessary Masks
Giacomo Giannini (Durham University)

part of: CLE Permanent Seminar on Metaphysics
March 18, 2022, 5:00pm - 6:30pm

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  • Support: grant #2021/11381-1, São Paulo Research Foundation (FAPESP)


University of Campinas
Pontifical Catholic University of Rio de Janeiro

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[All seminars] 17:00 to 18:30 pm (GMT+0)


In this talk, I'll argue that there is a tension between Dispositionalism –– the view that all metaphysical modality is grounded in actual irreducible dispositional properties –– and the possibility of time travel. I first present a potentiality-based version of the grandfather paradox, stating that the following theses are inconsistent: 1) time travel is possible, 2) powers fully ground modality, 3) self-defeating actions are impossible, 4) time-travellers retain their intrinsic powers upon time-travelling, and 5) time-travellers are ordinary agents. 

I will offer some arguments to the effect that we ought to accept premises (4) and (5). In order to do so, I will take a detour on the relation between powers, time, processes, and dated truths ––  statements that specify a particular time, like ``I can drink a cup of coffee at 8.15 on Wednesday 09/03/2022''. 

Finally, I'll show how the orthodox solutions to the paradox ––especially Lewis' –– cannot be applied, in virtue of the fact that powers are localised exact truthmakers. Indeed, I'll suggest to consider the inconsistency generated by the grandfather paradox as an instance of a more general and structural problem for dispositional theories of modality: that of necessary perfect masks (Vetter & Busse 2022).

I'll conclude by considering what the options are for the friend of powers, and argue that there is no cheap way out of the problem, short of a considerable overhaul of the theory.


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