The textual foundations of works of great cultural significance are often less stable than one would wish them to be. No work of Homer, Dante or Shakespeare survives in utterly reliable witnesses, be they papyri, manuscripts or printed editions. Notions of textual authority have varied considerably across the ages under the influence of different (and differently motivated) agents, such as scribes, annotators, editors, correctors, grammarians, printers and publishers, over and above the authors themselves. The need for preserving the written legacy of peoples and nations as faithfully as...