The long reign of Theodosius ii (408–50) was of crucial importance in cementing the separation of East and West into distinct, but closely linked, imperial systems; for the codification of Roman law in the form of the Codex Theodosianus of 437; for the role of major figures in the evolution of doctrine, or rather radical divisions over it (Cyril of Alexandria, Nestorius and Theodoret in the Greek East, Leo the Great in Rome); and, above all, as regards ecclesiastical history, for the two Councils of Ephesus, of 431 and 449. It was only because the victory of the Monophysites, with Theodosius' support, at the latter was abruptly reversed at Chalcedon, two years later, under a new emperor, that it was subsequently omitted from the established list of ecumenical councils. So this collection of eleven stimulating papers, the first being a sweeping sixty-page essay by Christopher Kelly, which serves to introduce the main themes of the others, deserves a warm welcome, and should be read by historians of government and culture, as well as of the Church. From the specific point of view of ecclesiastical history, the most relevant papers are those by Jill Harries on the nature of imperial decision-making, as revealed in the Codex and the Novellae of Theodosius; Richard Flower on the heresiology of the Codex, set against earlier examples of the systematic listing of heresies; and Thomas Graumann on the politics of the First Council of Ephesus. This last gives a foretaste of the translation and commentary on the (extremely confusing) acts of this council which is being prepared by him and Richard Price. It cannot be emphasised too strongly what an extraordinarily rich body of material is to be found in these acts, in Greek and Latin, edited by Eduard Schwartz. The papers in this volume bring out very vividly, firstly, the sheer range of material which survives from this reign; and, secondly, the way in which literary culture, government and divisions over doctrine were so closely related (note Mary Whitby in this volume on the Greek literature of the period). By its nature this collection offers a series of starting-points for interpretation, not a comprehensive coverage of the reign. A successor volume could look for instance at East-West relations at the level of both the two governments and the Church; or at the Second Council of Ephesus, known from detailed accounts in Greek, Latin and Syriac. But the reader of this volume is already offered valuable insights into one of the crucial periods in the history of the Christian Church.