 As we have seen, proponents of the Ability Hypothesis assume that the know-how which Mary acquires is distinct from any propositional knowledge. This assumption can be challenged, based for example on the work of Jason Stanley and Timothy Williamson (2001). On this view, for a subject S to know how to do something (to F) is for S to know that there is a way w for S to F, and for S to know this under a practical mode of presentation (2001, 430). Stanley &amp; Williamson themselves apply this thought to Lewis’s version of the Ability Hypothesis: