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). His other previous works include The Philosophical Foundations of Neuroscience (Blackwell, 2003) and History of Cognitive Neuroscience (Wiley-Blackwell, 2008), both co-authored with M.R. Bennett. Most recently he has published Human Nature: The Categorical Framework (Blackwell, 2007), the first volume of a trilogy on human nature.Together with Joachim Schulte, he has produced the 4th edition and extensively revised translation of Wittgenstein’s Philosophical Investigations (Wiley-Blackwell, forthcoming 2009).