I find the notion of outright belief pretty puzzling. I’m pretty inclined to take it to be a (probably context-sensitive or interest-relative) notion concerning degree of belief sufficiently close to certainty, or “practical certainty”.
One reason to think there’s a purely epistemic notion of outright belief I often here–when I’m holding forth about the sufficiency of assigning probabilities–is that to assign a probability n to some proposition p entails holding the outright belief that the probability of p is n. I don’t have a satisfying answer to this. I am quite certain that I am never fully certain in a probability judgment, but I’m completely at a loss as to what to do about higher-order probabilities (other than to punt to psychological limitations and say something like “Well, as many orders as I can ascend, the probabilities don’t dwindle that much.”)
Jeffrey gives a reply on p. 46 of _Probability and the Art of Judgment_ but it seems completely unconvincing to me. One move is to go operationalistc to some degree or other. Pure operationalism is a dead end, but it’s often hard to tell whether an approach–like that of Kaplan’s–is operationalistic or holistic. Every time I try to state or understand or defend a holistic view of what it is to assign a probability or make a probability judgment it sounds operationalistic. This is one of the very most frustrating problems to me.