P. M. S. Hacker is a Fellow of St. John's College Oxford. He is author of Insight and Illusion and Appearance and Reality (Blackwell, 1987). He edited The Renaissance of Gravure: the Art of S. W. Hayter. He has written a number of books with G. P. Baker: Wittgenstein: Understanding and Meaning (Blackwell, 1980), Wittgenstein: Rules, Grammar and Necessity (Blackwell, 1985), Language, Sense and Nonsense (Blackwell, 1984) and Scepticism, Rules and Language (Blackwell, 1984).