 According to a widely debated view in recent epistemology, contextualism, the truth conditions for knowledge attributions such as “S knows that P” are context-sensitive, due to the context-sensitivity of the cognitive verb “know” (for a review, see Rysiew 2016). Contextualists disagree over how to model the alleged context-sensitivity. Some say “know” is an indexical possessing a context-invariant character that is a function from contexts to contents (Cohen 2013). Others claim that “knows” is a vague predicate in need of contextual supplementation to predicate a determinate property (Heller 1999). Critics argue that leading contextualist proposals are ad hoc or unmotivated because we lack independent evidence that “knows” is context-sensitive in these ways (Stanley 2005), or because behavioral experiments demonstrate that people do not evaluate knowledge attributions in the way that leading contextualists have assumed or predicted (Turri 2016b).