Ludwig Wittgenstein is arguably he most important philosopher of the twentieth-century. In On Certainty he discusses central issues in epistemology concerning the nature of knowledge and sceptism. The Routledge Philosophy Guidebook to Wittgenstein and On Certaintyintroduces and assesses: Wittgenstein's life and the background to his early philosophy the central ideas and text of On Certainty,including its links with the arguments of G.E.Moore and its discussion of some fundamental issues in the theory of knowledge Wittgenstein's continuing importance and influence on contemporary philosophy. This Guidebookis essential reading for all students of Wittgenstein as well as those studying epistemology and philosophy of language.