Hilary of Poitiers (c 325-367/368) was the leading figure from the Western Church who promoted the cause of the Creed of Nicaea from the mid-350s until his early death a decade or so later. He was banished in 356 by the Emperor Constantius for reasons which are not clear and went to Phrygia, where he became an expert in the controversy over the full Godhead of Christ which was then dividing the Church. A theologian of moderate views, he played a leading role in reconciling churchmen divided more often by formulae than faith. He wrote extensively, both on the history of the controversy, in which he was himself a participant, and on its content. The first of the two translated texts in this volume is what remains of an historical work written by Hilary against two distinguished contemporary bishops, Valens and Ursacius, whose intervention on behalf of the Emperor Constantius Hilary thought disastrous. What remains consists mainly of extracts from the dossier of official texts Hilary had compiled. They throw light upon scenes of disarray, violence and betrayal in the Church life of the 4th century. Some brilliant lines of Hilary's are preserved here too.The second is an open letter to the Emperor Constantius, urging him to throw the weight of his authority behind the Nicene Creed. It failed to move the Emperor, but had its effect elsewhere.