P.M.S. Hacker is the leading authority on the philosophy of Wittgenstein. He is author of the four-volume Analytical Commentary on the Philosophical Investigations, the first two volumes co-authored with G.P. Baker, (Blackwell, 1980–96) and of Wittgenstein’s Place in Twentieth-century Analytic Philosophy (Blackwell, 1996). He has also written extensively on philosophy of language and philosophy of mind, most recently The Philosophical Foundations of Neuroscience (Blackwell, 2003), co-authored with M.R. Bennett.