This is one of the talks given by a PIBBSS Fellow at the PIBBSS '23 Symposium.

Abstract: Both CDT and EDT, the two most prominent decision theories, update on all the information they are provided. As a consequence, they present apparently irrational behavior in Parfit's Hitchhiker and Counterfactual Mugging. These are particular examples of the general phenomenon of dynamic instability: different instantiations of the agent (in different time positions or counterfactual realities) aren't able to cooperate. Updateless Decision Theory aims to solve dynamic instability completely, by having a single agent-moment decide all future policy. This is straightforward for the case of empirical uncertainty, where we can assume logical omniscience. But for logical uncertainty, we face more complicated tradeoffs, and in fact not even the correct formalization is clear. We propose a formalization using Garrabrant's Logical Inductors, develop desiderata for UDT, and present an algorithm satisfying most of them. We also explore fundamental impossibilities for certain dynamically stable agents, and sketch ways forward by relaxing dynamic stability.

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