Robbie Williams has just posted an excellent paper on Accuracy, Logic and Degree of Belief. I wanted to highlight one of parts with which I strongly agreed.
The overarching idea is that in adopting doxastic attitudes to a proposition, we incur commitment to persist in those attitudes if no new evidence is forthcoming (where persistence is understood as not changing one’s mind—-i.e. not adopting a different attitude to the same proposition. I discuss cases of simply ignoring the proposition below). In the limiting case, consider a situation where one simply moves from one moment to the next, with no new input or reflection. It would be bizarre to change ones (non-indexical) beliefs in such circumstances. Insofar as action, over time, is based on one’s beliefs, it would mean that a course of action started at one time might be abandoned (since it no longer maximizes expected utility) without any prompting from reflection or experience.
Persistence might be construed as a (widescope) diachronic norm on belief. Alternatively, a disposition to retain an attitude to the proposition over time might be constitutive of belief. If what makes something count as a belief is its functional role, then the reflections on extended action above motivate this kind of claim.
I think persistence is, at least for belief, both constitutive and normative. If a kind of state is not disposed to persist, that state is not belief. And if a token of that belief does not persist, in the absence of good reasons for it to be reconsidered, that’s a normative failing.
I ended up with a view like this via Richard Holton’s work. But I hadn’t realised it had an even more notable pedigree. At the Formal Epistemology Workshop, Hannes Leitgeb highlighted the work my colleague Louis Loeb has done in drawing attention to the importance of persistence to Hume’s theory of belief. (For a brief view of this, here is a review of Louis’s 2002 book.)
There has been a lot of work recently on the existence of diachronic norms for belief. I think I’ll start calling the view that there are such norms, and they are primarily norms of persistence, the Humean view. It has a better claim to being genuinely Hume’s view than most views I call Humean!