An argument of Parfit's reconsidered with logical decision theory

A LessWrong contributor reconsiders Derek Parfit's argument about self-interest as a theory of rationality. Parfit showed it's self-defeating in the prisoner's dilemma: if everyone rationally pursues self-interest, everyone defects and ends up worse off than they would have cooperating. But apply logical decision theory, and the math changes. A self-referential version asks: what would be best for this theory to recommend? In a symmetric game where both players share the same theory, that logic points to cooperation, not defection, so both players win. The catch is that reasoning requires counterpossibles—hypothetical reasoning about what would happen if a logical fact were different—and the author acknowledges this gets philosophically murky. Still, they argue the exercise is a sign that the wider field of logical decision theory deserves serious philosophical treatment.

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