The discovery, in various quarters, of hitherto unknown letters exchanged between Wittgenstein and the chief of his Cambridge friends has stimulated the editors to produce a fundamentally new volume. Their notes too are based on archival material not previously explored. Wittgenstein's correspondents here are not his disciples but those he recognized as his mentors - Bertrand Russell, G.E. Moore, J.M. Keynes, and later Frank Ramsey and (represented by a single but important letter) Piero Sraffa. Often their reactions are as interesting as his own. Wittgenstein appears as in turn shy and affectionate, fierce and censorious, happy to collaborate and sure of his own judgement. Four quarrels and four reconciliations are documented. Wittgenstein's struggles to publish his "Tractatus" can be followed, his retreat from the world, his being wooed back to philosophy, all in the end reversed. A constant theme, despite ambivalence, is the pull of the Cambridge that these friends represented. It was as important to his as his solitudes, for it was from there, true to its motto, that he drew light and draughts of inspiration.