Dispositionalism’s (grand)daddy issues: time travelling and perfect masks

Abstract

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. This is due to the fact that Dispositionalism makes it much harder to solve a potentiality-based version of the grandfather paradox. We 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 with basic intrinsic potentialities. We then consider a number of potential solutions, and find them wanting. We argue that the metaphysical impossibility of performing a self-defeating action acts as a necessary perfect mask––while time-travel lets us “slip” the potentiality under the mask, thus generating the contradiction. We conclude considering what are the options for the dispositionalist.

The Close Possibility of Time Travel

“…Similarly, there is a ban on things travelling faster than the speed of light, but we might presume that this does not apply to certain things, e.g., shadows and gerrymandered objects [99] (pp. [21][22]. But even if we allow this and have it that LAW 1 is restricted to sub-atomic particles, it would not explain the fictional narrative.…”

“…Physical possibility is only one such candidate (e.g., Klimov's Come and See is physically possible whilst Lucas's Star Wars is not); moreover, in the context of science fiction, it is unlikely to be of much interest. Certainly, when it comes to time travel, broader modalities are normally our focus, e.g., logical possibility [1,5,[12][13][14][15][16][17], metaphysical possibility [3,[18][19][20][21][22][23], conceptual possibility [24], or absolute possibility [25,26].…”