Here's a question which I've been thinking about for a while but which I got a bit clearer on this weekend: have we successfully naturalized epistemic normativity if, for every epistemically normative claim, we can identify the fact which makes true, and it turns out to be a natural fact?
I'm tempted to say yes. The view could be that (for example) claims like:
(1) S's belief that p is epistemically correct
are made true by the same facts as claims like:
(2) (S believes that p and) given S's information, p is probably true.
This sort of view appears to raise an analogue of the Open Question Argument. It could be objected that the normativity of (1) is not adequately captured by (2) because one can agree that p is probably true given S's situation, but still wonder whether S's belief that p is epistemically correct.
One can respond that it need not be part of the view that (1) means the same as (2), and that therefore the identity between the facts which make these two claims true need not be at all obvious. If there is meant to be more to the objection than this, it's not clear what it is. To insist that the question of the correctness of S's belief remains genuinely open when you know that (2) is true is just to beg the question against the view that the fact which makes (1) true is the fact that makes (2) true.