P. M. S. Hacker is Fellow of St. John's College, Oxford. He is author of Insight and Iffusion (1972, revised ed. 1986), Appearance and Reality (Blackwell, 1987) and Wittgenstein: Meaning and Mind (Blackwell, 1990). He edited The Renaissance of Gravure: The Art of S. W. Hayter (1988), Graure and Grace: the Engravings of Roger Vieillard (1993) and co-edited a Festschrift for H. L. A. Hart together with J. Raz. Law, Morality and Society (1977). He has written five books with G. P. Baker, Wittgenstein: Understanding and Meaning (Blackwell, 1980), Wittgenstein: Rules, Grammar and Necessity (Blackwell, 1985), Frege: Logical Excavations (Blackwell and Oxford University Press, New York, 1984), Language, Sense and Nonsense (Blackwell, 1984), and Scepticism, Rules and Language, (Blackwell, 1984).