According to a familiar story, beliefs qualify as knowledge only if they can be justified on the basis of impeccable first premisses via equally immaculate first principles. The story has no truth to it. Centuries of criticism suggest that our interesting beliefs are born on the wrong side of the blanket.

Fixating on the pedigrees of our beliefs is unlikely to be helpful in any case. We use our beliefs as resources for inquiry and deliberation. That is to say, we assume the truth of our beliefs as premisses in justifying our decisions and in justifying revisions of these beliefs. When they are so used, a question of justification does not arise. We may, indeed, be concerned to justify a revision of our assumptions either by adding items to them or removing others from them. But the premisses used in such justifications are precisely the assumptions endorsed prior to such modification. These assumptions, while they are themselves being used as premisses, do not stand in need of justification.

From the point of view of X (who may be a person or group acting in concert such as a scientific community) at time t, there is no relevant distinction to be made between what X fully believes at t and what he knows at t.