October 3, 2022

That Does Not Compute: David Lewis on Credence and Chance

Gordon Belot (University of Michigan)

Abstract: Following Lewis, many philosophers hold reductionist accounts of chance (on which claims about chance are to be understood as claims that certain patterns of events are instantiated) and maintain that rationality requires that credence should defer to chance (in the sense that  one’s credence in an event, conditional on the chance of that event being x, should be x).  It is a shortcoming of an account of chance if it implies that this norm of rationality is unsatisfiable by computable agents. Here it is shown, using elementary considerations from the theories of inductive learning and of algorithmic randomness, that this shortcoming is more common than one might have hoped.