When to take one box, when to take two: A concrete analysis of Newcomb's problem

Abstract

Fifty-seven years of debate have not led to a consensus on Newcomb's problem. I argue that this failure comes from not viewing the problem in concrete terms, for which common-sense intuitions are clearly applicable. If near-perfect predictions are not required - only predictions good enough that Evidential Decision Theory (EDT) recommends taking only one box - Newcomb scenarios without any fantastic elements are actually feasible. I give a detailed account of such concrete scenarios, in which the decision-maker has varying amounts of information about the prediction process. I argue that in these scenarios it is rational to take both boxes, as Causal Decision Theory (CDT) recommends. To make this more convincing, I introduce a simpler impersonal Newcomb problem, also with a concrete realization, to help bridge causal intuitions from everyday decisions to the standard Newcomb scenario. I also argue that Newcomb's problem with nearly perfect predictions can only be realized by a (currently fantastic) process in which the Predictor accurately simulates the thoughts of a Participant. In a functionalist view of consciousness, this simulation will be a conscious entity, whose experience will not be distinguishable from that of a ``real'' person. In this scenario, CDT recommends taking one box. I conclude that when Newcomb's problem is properly analysed in concrete terms, CDT gives the correct answer in all scenarios.