Incorporating significant editorial changes from earlier editions, the fourth edition of Ludwig Wittgenstein's _Philosophical Investigations_ is the definitive _en face_ German-English version of the most important work of 20th-century philosophy * The extensively revised English translation incorporates many hundreds of changes to Anscombe’s original translation * Footnoted remarks in the earlier editions have now been relocated in the text * What was previously referred to as ‘Part 2’ is now republished as _Philosophy of Psychology – A Fragment_, and all the remarks in it are numbered for ease of reference * New detailed editorial endnotes explain decisions of translators and identify references and allusions in Wittgenstein's original text * Now features new essays on the history of the _Philosophical Investigations_, and the problems of translating Wittgenstein’s text