“Center Indifference and Skepticism”David Builes (Princeton University)
Abstract: Many philosophers have been attracted to a restricted version of the principle of indifference in the case of self-locating belief. Roughly speaking, this principle states that, within any given possible world, one should be indifferent between different hypotheses concerning who one might be within that possible world, so long as those hypotheses are compatible with one’s evidence. Such a principle has been used to argue that certain physical theories imply that we are most likely Boltzmann brains, and it has been used to argue that we are probably living in a computer simulation. After responding to some existing objections to this indifference principle, I argue that the relevant indifference principle is crucially ambiguous, and I defend a more precise version of the principle that is sensitive to one’s prior metaphysical beliefs. In particular, I argue that how the principle should be applied should be sensitive to one’s views about the concrete existence of other times and possible worlds. I close by arguing that standard presentations of the Boltzmann brain argument and the simulation argument are only valid given certain views in the metaphysics of time, and a powerful argument for inductive skepticism can be given under certain views in the metaphysics of modality.