The received definition of knowledge (as true, evident belief) has recently been questioned by Edmund Gettier with an example whose principle is as follows. A proposition, p, is both evident to and accepted by someone S, who sees that its truth entails (would entail) (that either p is true or q is true). This last is thereby made evident to him, and he accepts it, but it happens to be true only because q is true, since p is in fact false. Hence, inasmuch as he has no evidence for the proposition q, S can hardly be said to know (that either p is true or q is true). Here then is a formula for true, evident beliefs that are not cases of knowledge. I discuss the possibility of adding a fourth condition to this triad.