 We also learn something else though, something more constructive: that Hume’s problem is a close cousin of the problem of the priors. If we could justify Carnap’s way of assigning prior probabilities, we would be well on our way to solving Hume’s problem. (Why only on our way? More on that in a moment, but very briefly: because we’d still have to justify using conditional probabilities as our guide to the new, unconditional probabilities.) Can we justify Carnap’s two-stage scheme? This brings us to a classic debate in formal epistemology.