Description:

Title: (Epistemic) Probabilities are Degrees of Support, not Degrees of (Rational) Belief

Abstract: I argue that when we use ‘probability’ language in epistemic contexts – e.g., when we ask how probable some hypothesis is, given the evidence available to us – we are talking about degrees of support, rather than degrees of belief. The probability of A given B is the (mind-independent) degree to which B supports A, not the degree to which someone with B as their evidence believes A, or the degree to which someone would or should believe A if they had B as their evidence. My central argument is that degrees of support can correctly model good reasoning in cases of old evidence where degrees of belief cannot. I consider ways to revise orthodox degree-of-belief Bayesianism in order to account for this kind of case, and argue that such revisions end up unable to account for reasoning about probabilities conditional on evidence that it is impossible not to possess.