Suppose you hold to the following view regarding coarse and fine belief: they are metaphysically determinable and determinate respectively, because the latter metaphysically makes for the former. This is a view defended in a recent paper by Sturgeon and one of its attractions is that it explains why coarse and fine grained belief generate action in concert. There's an objection that seems to me too obvious to be good, but here it is. Necessarily, the mere fact that ~p means that mental state MS1 is mistaken if MS1 is the belief that p. The mere fact that ~p does _never_ means that mental state MS2 is mistaken if MS2 is a level of confidence in the truth that p less than certainty. On any Lockean view worth its salt, a belief that p can consist of a level of confidence less than certainty. But, it seems to follow that MS1 is not MS2. But, it seems that we'd want to say that MS1 could be MS2 in just the same sense that the red of this cup could be an instance of scarlet.
I've just tried to fix this post in light of Mike's suggestions. See here.