T.S. Eliot's early drafts of his poetic masterpiece The Waste Land famously used an offbeat line from Dickens as a rather cryptic working title: "He Do the Police in Different Voices'. These words might serve equally well — perhaps, indeed, rather better — as a title to a philosophical masterpiece by one of Eliot's contemporaries: Ludwig Wittgenstein's Philosophical Investigations. At some points in Philosophical Investigations, Wittgenstein shamelessly violates the rules of ordinary language — only to be stopped and cautioned by another voice, which goes on to spell the rules out. At other times, he gets lost and asks for directions — whereupon a different voice emerges from the text to set him back on track. If the text is loitering, a voice will speak up to move it on; if the text is rushed, a voice will slow it down and pull it over for speeding. The word "Investigations' in Wittgenstein's title suggests detective work,¹ but in actual fact his philosophical practice has as much in common with an old-fashioned bobby on the beat, walking down the mean streets of linguistic philosophy.²