First published in 2005. The essays and replies in this volume represent, with some modifications, the proceedings of a colloquium held in Oxford in Trinity Term, 1979. With occasional exceptions, critical response to the Philosophical Investigations following publication focused on a limited range of topics - an unsystematic book was discussed in an unsystematic fashion. This book employs a different approach, one that interprets disconnected discussions of Wittgenstein's as united by a single underlying set of powerful arguments.