When T. S. Eliot summed up his life’s work in 1963, two years before he died, it was in a Collected Poems of fewer than 250 pages. But when Christopher Ricks and I published The Poems of T. S. Eliot in 2015, the two volumes ran to some two thousand. Where did the other 1,750 pages come from? What is this new edition, and what does it mean to ‘edit’ poetry anyway?