"Anyone reading Philosophical Investigations would do well to keep it by their side, not only for its authoritative commentary on particular passages, but also for Hacker's extremely illuminating essays on the themes of the last part of the book: one each on intentionality, induction, the arbitrariness of grammar, negation, methodology in philosophical psychology, memory and recognition the will, intention and the mythology of meaning." London Review of Books "It is as good a commentary on the Investigations as seems humanly possible. This will reamin the definitive starting point for the forseeable future. Indeed, it must rank alongside the greatest contributions to philosophical scholarship (such as Ross on Aristotle or Vaihinger on Kant), since it combines, on a momentous scale, authoritative textual exegesis, philosophical insight, encyclopedic knowledge of the historical background and lucidity of expression. Hacker succeeds brilliantly in showing that these passages are essential to the discussion of language and linguistic meaning that is the leitmotif of the Investigations. The chapter on mental states and processes provides an excellent interpretation and defence of Wittgenstein's approach to philosophical psychology, in particular of his denial that our psychological concepts constitute a 'folk psychology' that must be replaced by a more scientific alternative. Similarly, the chapter on will is the most authoritative discussion yet of Wittgenstein's fiendishly difficult treatment of that topic." Hans-Johann Glock, Times Higher Education Supplement