 On Certainty is generally accepted as a work of epistemology, as opposed to PPF, which is usually recognized as dealing with psychology (though even that distinction is called into question by some interpretations). It tackles skeptical doubts and foundational solutions but is, in typical Wittgensteinian fashion, a work of therapy which discounts presuppositions common to both. As always before in the interpretative game, the general view sees Wittgenstein as landing on the non-skeptical side of the epistemological debate, choosing instead to peruse “hinge propositions.” These are propositions about which doubt cannot be entertained, but whether this be due to their being epistemically foundational, naturally certain, or logically unavailable to doubt is still a matter for philosophical explanation; as is the question of Wittgenstein’s object of critique – Cartesian or radical skepticism – or, in some quarters, the very assumption of his unequivocal anti-skepticism. This is intimately related to another of On Certainty’s themes—the primacy of the deed to the word, or, in Wittgenstein’s PI terminology, of form of life to logos. Such a clearly delineated philosophical phase has garnered the recognition of a “third Wittgenstein” (initially by Danièle Moyal-Sharrock).