The seventh century is often regarded as the beginning of the Byzantine Dark Ages: with the rise of Islam and the conquest of the eastern and southern provinces of the empire, Byzantium entered on a period during which for a century or so little was recorded. So far as theology is concerned, however, the seventh century initiates one of the most productive periods in the history of Byzantine thought, including luminaries such as St Maximos the Confessor and St John Damascene. It also opened up a period of controversy, beginning with the Christological dispute brought about by the attempts by the imperial court to fashion some kind of compromise between Orthodox Chalcedonianism and those who rejected Chalcedon, called by their opponents Monophysites. For his defence of Orthodoxy, Maximos eventually lost his life. The fully-fledged heresy, that to some extent endured among the Maronites, was called monothelitism, the doctrine that Christ had one will. It was preceded by monenergism, the doctrine that Christ had only a single divine-human (‘theandric’) activity. The beginning of the controversy occurred when in 633 Sophronios, the former learned companion of John Moschos, soon to become patriarch of Jerusalem, protested against the monenergist doctrine of the agreement brokered by the patriarch of Alexandria, Kyros, who came from Lazica, the region where Maximos, in exile, eventually died. In this volume Pauline Allen has provided the text and translation of the Synodical letter issued by Sophronios as the newly elected patriarch of Jerusalem in 633, together with the various surviving letters that relate to the progress of the monenergist/monothelite enterprise. She provides, too, an extensive introduction and detailed notes. As well as providing information about the background to the controversy for which Maximos gave his life, Pauline Allen also places the Synodical letter in its context as a rare example of what must have been a common genre: the letter sent by a newly elected patriarch to his fellow patriarchs to assure them of his orthodox credentials. Sophronios's synodical letter is very long and includes an extensive list of heresies that constitutes an important witness to the development of such lists that are a feature of the definition of Orthodoxy from Hegesippos's second-century list to John Damascene's On heresies, via Epiphanios's definitive work, the Panarion (or ‘Medicine Chest’, suggesting that the purpose of such lists was to provide a diagnostic of error), and beyond, to documents like the Synodikon of Orthodoxy, first promulgated in 843 at the end of the Iconoclast controversy, and still proclaimed (at least in theory) on the first Sunday of Lent in the Orthodox tradition. This is a welcome addition to Oxford Early Christian Texts; it is only a pity that it is so expensive.