Those who recognize the type of knowledge acquisition that involves what Peter D. Klein calls ‘a useful false belief’ face the problem of defining appropriate boundaries for such a belief. Klein’s own proposal encounters counterexamples and should be replaced by a definition inspired by a position that may be called ‘circumstantialism,’ which emphasizes certain circumstances belonging to the knower’s situation. The revised definition also offers a solution to ‘The False Lemma Problem’ of distinguishing cases involving useful false beliefs from classic (...) Gettier-type cases involving a false lemma in the reasoning underlying the inferential process. (shrink)