Those of us who were in Ludwig Wittgenstein's classes during his last years at Cambridge had no doubt how lucky we were, or how unique our experience was. To be present in his sparsely furnished attic room at Trinity College was to watch a deeply reflective man judge his own ideas by critical standards more stringent than any we knew existed; and no serious minded student could shirk the task of figuring out what demands Wittgenstein was imposing on himself. He was no less impressive when "at leisure" — though to use that phrase of Ludwig Wittgenstein sounds almost frivolous — e.g., on the regular visits he paid G. E. Moore and his wife Dorothy in their house on Chesterton Road. (In 1946–47, I lived in the converted garage at the bottom of their garden.) Then the richness of his cultural background and the intensity of his concern — above all, with music — shone out in conversations which, in many ways, deserved to be recorded almost as much as his lectures.