“Contemporary analytic philosophers of mind generally use the term “belief” to refer to the attitude we have, roughly, whenever we take something to be the case or regard it as true. To believe something, in this sense, needn’t involve actively reflecting on it: Of the vast number of things ordinary adults believe, only a few can be at the fore of the mind at any single time.
“Nor does the term “belief”, in standard philosophical usage, imply any uncertainty or any extended reflection about the matter in question (as it sometimes does in ordinary English usage). Many of the things we believe, in the relevant sense, are quite mundane: that we have heads, that it’s the 21st century, that a coffee mug is on the desk.
“Forming beliefs is thus one of the most basic and important features of the mind, and the concept of belief plays a crucial role in both philosophy of mind and epistemology. The “mind-body problem”, for example, so central to philosophy of mind, is in part the question of whether and how a purely physical organism can have beliefs. Much of epistemology revolves around questions about when and how our beliefs are justified or qualify as knowledge.” (continue article)
— Eric Schwizgebel in Stanford Encyclopedia of Philosophy