Newcomb's Problem,Prisoners' Dilemma,and collective action

Among various cases that equally admit of evidentialist reasoning, the supposedly evidentialist solution has varying degrees of intuitive attractiveness. I suggest that cooperative reasoning may account for the appeal of apparently evidentialist behavior in the cases in which it is intuitively attractive, while the inapplicability of cooperative reasoning may account for the unattractiveness of evidentialist behaviour in other cases. A collective causal power with respect to agreed outcomes, not evidentialist reasoning, makes cooperation attractive in the Prisoners' Dilemma. And a natural though unwarranted assumption of such a power may account for the intuitive appeal of the one-box response in Newcomb's Problem.This paper was originally submitted to Synthese in March 1989. For helpful comments and criticisms of earlier versions I am grateful to Michael Bacharach, John Broome, David Gauthier, Isaac Levi, Adam Morton, Derek Parfit, Howard Sobel, Robert Sugden, Bas van Fraassen, and members of audiences on various occasions on which I have presented this paper. I am also grateful to the Humanities Council of Princeton University for their generous support during the period when this paper was written.