Newcomb’s Problem as Cognitive Illusion

Richard Jeffrey (1983) has said that Newcomb’s Problem may be seen as a rock on which Bayesianism must founder. Despite a vast literature of great technical subtlety and complexity, no solution has emerged. Most recently, Jeffrey (2004) renounced his earlier position and no longer regards Newcomb’s problem as a genuine decision problem at all. Rather, Jeffrey suggests, “Newcomb problems are like Escher’s famous staircase on which an unbroken ascent takes you back where you started.” Jeffrey’s analogy is apt for a puzzle whose specific logical features can be precisely articulated. I offer a novel analysis of the problem going beyond mere analogy to reveal the source of its persistent intractability. In the spirit of Jeffrey’s analogy, I propose that the central problem has arisen from the misguided attempt to reconcile the impossible science-fictional features of the story with a plausible causal analysis and, therefore, the contest between causal and evidential decision theories is misconceived. As the analogy with Escher figures suggests, Newcomb’s Problem is an instance of a compelling cognitive illusion whose underlying mechanism is proposed here