 Whenever a knower (S) knows some fact (p), several conditions must obtain. A proposition that S doesn’t even believe cannot be, or express, a fact that S knows. Therefore, knowledge requires  belief.[14]  False propositions cannot be, or express, facts, and so cannot be known. Therefore, knowledge requires truth. Finally, S’s being correct in believing that p might merely be a matter of luck. For example, if Hal believes he has a fatal illness, not because he was told so by his doctor, but solely because as a hypochondriac he can’t help believing it, and it turns out that in fact he has a fatal illness, Hal’s being right about this is merely accidental: a matter of luck (bad luck, in this  case).[15]  Therefore, knowledge requires a third element, one that excludes the aforementioned luck, and so that involves S’s belief being, in some sense, justifiably or appropriately held. If we take these three conditions on knowledge to be not merely necessary but also sufficient, then: S knows that p if and only if p is true and S justifiably believes that p. According to this account, the three conditions—truth, belief, and justification—are individually necessary and jointly sufficient for knowledge of  facts.[16]