M. S. Hacker is Emeritus Research Fellow at St John's College, Oxford. He is the leading authority on the philosophy of Wittgenstein and the author of the four-volume Analytical Commentary on the Philosophical Investigations (Blackwell, 1980-96) the first two volumes co-authored with G. P. Baker (2nd revised eds, 2003, 2009) and of Wittgenstein's Place in Twentieth-century Analytic Philosophy (Blackwell, 1996). He has also written extensively on philosophy of mind, including Philosophical Foundations of Neuroscience (Blackwell, 2003) and History of Cognitive Neuroscience (Wiley-Blackwell, 2008), co-authored with M. R. Bennett, and Human Nature: The Categorial Framework (Blackwell, 2007), the first volume of a trilogy on human nature. Joachim Schulte teaches philosophy at the University of Zurich. He is also a professional translator, and editor of Wittgenstein's writings. He edited the authoritative critical-genetic edition of Wittgenstein's Philosophische Untersuchungen (Suhrkamp, 2001). He is author of Wittgenstein - an Introduction (1989), Chor und Gesetz: Wittgenstein im Kontext (Suhrkamp,1990), Experience and Expression - Wittgenstein's Philosophy of Psychology (Clarendon Press, 1993), and of many dozens of philosophical papers.