When I and Tom came up with that, I don't think we meant "be­lief" to be im­bued with the usual philo­soph­i­cal con­no­ta­tions. Rather, we in­tended it to mean some­thing like "ac­tion-guid­ing, in­tro­spec­tively ac­cessible rep­re­sen­ta­tion of a state of af­fairs ex­ist­ing in­de­pen­dently of whether it is queried".
When peo­ple ask me what I think about the world, I can of­ten come up with lots of in­tel­li­gent sound­ing an­swers—but it is un­for­tu­nately more rare that my ac­tual ac­tions, plans and nor­ma­tive eval­u­a­tions are some­how suit­ably hooked up to, and cru­cially de­pend upon, those an­swers.