Metaphysics and Epistemology Group (Tuesday - Week 2, MT23)

According to Time-Slice Rationality, the requirements of rationality should make no reference to the relation of personal identity across time. One of the main motivations behind Time-Slice Rationality is that it allows epistemologists to avoid getting entangled in metaphysical puzzles concerning identity across time. However, just as there are metaphysical puzzles concerning identity across time, there are also metaphysical puzzles concerning identity across possible worlds. The goal of this paper is to generalize Time-Slice Rationality to World-Bound Rationality, which is the thesis that the requirements of rationality should make no reference to the relation of personal identity across possible worlds. After formulating and defending this generalization, I turn to explore its first-order implications. In particular, I argue that World-Bound Rationality leads to the “Relevance-Limiting Thesis” in the epistemology of self-locating belief, according to which self-locating evidence is never evidentially relevant to non-self-locating beliefs. I conclude by suggesting some further areas in epistemology where World-Bound Rationality might have interesting first-order implications.