On CertaintyThe German text, with a facing English translation by P. M. S. Hacker. Ludwig Wittgenstein's On Certainty collects the final notes of one of the twentieth centurys most influential thinkers, written during the last eighteen months of his life. These posthumously published fragments reflect on questions of knowledge, doubt, and belief. They offer a distinctive perspective on Wittgenstein's late philosophy and contain many remarks which have greatly