Contrary to my general plan, I have thought it wiser, in the matter of the Eutychian controversy, to include other than Leo’s own writings, that the reader may fulfil the precept audi alteram partem in what was the most important doctrinal discussion of Leo’s term of office. This Letter (XXI.) bears the stamp of genuineness upon it, though the Gk. original is not found. It is from a collection of documents bearing on Nestorianism published ex ms. Casinensi, first by Christianus Lupus (?), and afterwards by Stephanus Baluzius (1630–1718).