We will be looking at Reasons Without Persons by Brian Heddon. Specifically focus on 1-1.2 and 3-3.2.

This book is an extended defense of Time-Slice Rationality, the view that for purposes of rational evaluation, the relationship between two time-slices of the same person is not importantly different from the relationship between time-slices of distinct persons. The locus of rationality is the time-slice rather than the temporally extended agent. What you rationally ought to believe, desire, or do at a time depends only on your mental states at that time. It does not depend on what you believe, desire, or do at other times. Time-Slice Rationality is motivated by two goals. The first is to insulate the theory of rationality from thorny issues in the metaphysics of personal identity over time, which, it is argued, are irrelevant to what rationality requires of you. The second is to vindicate the thought that being rational is about believing and behaving in ways that are sensible, given your perspective on the world. Time-Slice Rationality conflicts with some well-known Bayesian principles of rationality, but these principles are independently problematic, and they can be replaced by time-slice-centric principles that do all the work that the old principles were supposed to do while avoiding their pitfalls. In this way, we can put the theory of rationality on firmer foundations by taking seriously Parfit’s claim that personal identity is of no great significance.