 Skepticism might also result from the assumption that, if a belief formation method M were, in some situation, to yield a belief without enabling us to know the truth of that belief, then it cannot ever generate bona fide knowledge (of that sort of belief), no matter what circumstances it is used in. (M must be strengthened somehow, say with a supplemental method, or with evidence about the circumstances at hand, if knowledge is to be procured.) This assumption might rest on the idea that any belief M yields is, at best, accidentally correct, if in any circumstances M yields a false or an accidentally correct belief (Luper 1987b,c). On this assumption, we can rule out a method of belief formation M as a source of knowledge merely by sketching circumstances in which M yields a belief that is false or accidentally correct. Traditional skeptical scenarios suffice; so do Gettieresque situations. Externalist theorists reject the assumption, saying that M can generate knowledge when used in circumstances under which the belief it yields is not accidentally correct. In highly Gettierized circumstances M must put us in an especially strong epistemic position if M is to generate knowledge; in ordinary circumstances, less exacting methods can produce knowledge. The standards a method must meet to produce knowledge depend on the context in which it is used. This view, on which the requirements for a subject or agent S to know p vary with S’s context (e.g., how exacting S’s method of belief formation must be to yield knowledge depend on S’s circumstances), might be called agent-centered (or subject) contextualism. Both tracking theorists and safe indication theorists defend agent-centered contextualism.