Jens Jäger

Philosophical investigations into the nature of chance and causation have typically assumed classical spacetime backgrounds. My dissertation argues that this practice misses important lessons. By tying chance functions to a global time parameter—a structure of classical spacetimes—orthodox theories of chance cannot state important Markov-style principles and fail outright in spacetimes that lack a linear time structure, e.g. due to closed time-like curves. By contrast, the urchance approach, developed in the dissertation's first half, assumes no such parameter, works in any spacetime geometry, captures the needed independence principles, and resolves the puzzle of chances on closed time-like curves. Two general morals follow: chance isn't as intimately tied to time or causation as is usually thought, and chances can vary even across intrinsically duplicate trials. On the causation side, counterfactualist reductions are unable to deal with synchronic nomic constraints—law-based, yet non-causal, links between simultaneous events. These constraints occur not only in temporal-loop geometries but also in common-or-garden theories like Maxwellian electrodynamics. To save the counterfactualist approach to causation, its defenders must separate genuinely dynamical counterfactual influences from those produced solely by synchronic constraints.

Suppose your evil sibling travels back in time, intending to lethally poison your grandfather during his infancy. Determined to save grandpa, you grab two antidotes and follow your sibling through the wormhole. Under normal circumstances, each antidote has a 50% chance of curing a poisoning. Upon finding young grandpa, poisoned, you administer the first antidote. Alas, it has no effect. The second antidote is your last hope. You administer it---and success: the paleness vanishes from grandpa's face, he is healed. As you administered the first antidote, what was the chance that it would be effective? This essay offers a systematic account of this case, and others like it. The central question is this: Given a certain time travel structure, what are the chances? In particular, I'll develop a theory about the connection between these chances and the chances in ordinary, time-travel-free contexts. Central to the account is a Markov condition involving the boundaries of spacetime regions.

I argue that a popular view about self-locating evidence implies that there are cases in which agents have surprisingly strong evidence for their own reincarnation. The central case is an ‘Immortal Beauty' scenario, modelled after the well-known Sleeping Beauty puzzle. I argue that if the popular ‘thirder’ solution to the puzzle is correct, then Immortal Beauty should be confident that she's going to be reincarnated. The essay also examines another pro-reincarnation argument due to Michael Huemer (2021). I argue that his argument fails, and that my argument establishes an alternative way in which mere existence can be evidence for reincarnation. I then examine whether my result generalizes.