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