The Trembling Stoic
On a dispositionalist view of belief (which I elaborate in this essay and this encyclopedia entry), to believe some proposition P is just to act and react, both in one's outward behavior and one's inward feelings, as though P were the case. One difficulty for this sort of view is what to do when someone seems to sincerely, wholeheartedly endorse some proposition -- and hence, we might say, believe it -- and yet does not pervasively act and react as though that proposition were true.
Excluding cases of deception (self or other) or unusual cognitive background (such as strange accompanying beliefs and desires), such cases seem to come mainly in two varieties:
(1.) Trembling Stoic cases. The Stoic sincerely judges, both alone in his study and out in the world in discussions with others, unhesitantly and unreservedly, that death is not bad. Yet he trembles before the sword, and he fears what the doctor will say. Or: A liberal professor sincerely professes that all the races are intellectually equal (and has, let's suppose, the scientific evidence to prove it), yet reveals implicitly in her behavior and reactions a subtle but persistent racism when it comes to matters of intelligence. Or: Someone comes to believe that God and Heaven exist, but does not transform her behavior accordingly.
These cases needn't involve self-deception or insincerity. One may perfectly well realize the need to reform. Nor are such cases necessarily matters of "weakness of will" in the face of acute, impulsive desires: Our liberal professor, for example, need have no particular desire to treat other races as intellectually inferior.
(2.) Momentary forgetfulness cases. I get an email saying a bridge I normally take to work is closed. Yet the next day, I find myself headed toward the bridge, rather than my intended alternate route, until at some moment (maybe only after seeing the bridge) I recall the previous day's email. Or: The trashcan used always to be under the sink, now it's by the fridge. I still reach under the sink half the time, though, when I go to throw something away.
Aaron Zimmerman, Tori McGeer, and Ted Preston have emphasized the importance of such cases to me in evaluating dispositionalism about belief (Tori and Ted being sympathetic to dispositionalism, Aaron less so).
My response to such cases is to distinguish broadly dispositional belief from momentary occurrences of sincere judgment. Then I'll "bite the bullet" on belief: The Stoic, the absent-minded driver, do not fully and completely believe, respectively, that death is not bad, that the bridge is closed (neither do they fully and completely believe the opposite). Although there are moments when they make sincere judgments to that effect, it takes a certain about of work and self-regulation to allow such judgments fully to inform one's habitual everyday behavior. Until that work is done, they don't fully believe.
(I recognize that it may grate a bit to say that I don't believe that the bridge is closed, as I'm driving toward it, especially since it seems right for me to say, in retrospect, "I knew the bridge was closed!" Here's a brief discussion of that particular issue.)