Rush Rhees, a close friend of Wittgenstein and a major interpreter of his work, shows how Wittgenstein's On Certainty concerns logic, language, and reality – topics that occupied Wittgenstein since early in his career.

• Authoritative interpretation of Wittgenstein's last great work, On Certainty, by one of his closest friends.
• Debunks misconceptions about Wittgenstein's On Certainty and shows that it is an essay on logic.
• Exposes the continuity in Wittgenstein's thought, and the radical character of his conclusions.
• Contains a substantial and illuminating afterword discussing current scholarship surrounding On Certainty, and its relationship to Rhees's work on this subject.

Rush Rhees (1905–89) was one of Wittgenstein’s closest friends and his literary executor. He taught at Swansea from 1940 to 1966. Amongst Wittgenstein’s posthumous works edited by Rhees are Remarks on the Foundations of Mathematics (1956), Blue and Brown Books (1958), Philosophical Remarks (1964), Lecture On Ethics (1965) and Philosophical Grammar (1969). Rhees is also the author of Discussions of Wittgenstein (1970, 1996) and Wittgenstein and the Possibility of Discourse (1998).

D. Z. Phillips is Professor of Philosophy Emeritus and Rush Rhees Professor Emeritus at the University of Wales, Swansea, and Danworth Professor of the Philosophy of Religion at Claremont Graduate School, California. He has published widely in the philosophy of religion and ethics; some of his more recent books include Interventions in Ethics (1992), Wittgenstein and Religion (1993) and Religion and the Hermeneutics of Contemplation (2001). He is also editor of the Blackwell journal Philosophical Investigations.