The circumstances in which Roman rule over Britain came to an end have always been something of a puzzle to historians. There is of course no contemporary record giving a continuous narrative of the relevant events, and the few brief notices in ancient sources about British affairs in the first two decades of the fifth century come from writers of various dates and degrees of authority, none of whom seems to have had any first-hand knowledge of what took place. It is, therefore, hardly surprising that what they say should be subject to wide differences of interpretation, differences all the wider because some of the interpreters have been viewing the events from the standpoint of later English history and without an intimate knowledge of the Roman Empire in the fifth century. And it must further be admitted that, among scholars familiar with the conditions of this age, there has been something of a gap between those concerned with matters of history, whether political, administrative, social, or economic, and those concerned with thought and opinion, and primarily, of course, as theologians with the development of Christian doctrine in the great age of Ambrose, Jerome, and Augustine. It is easy for theologians to forget that the immense creative achievement of these thinkers was carried out at a time when the foundations of the society they knew were collapsing under external pressure and internal strain, and it is easy for historians to forget that a society riddled with corruption and precariously held together by the barbarous methods of a repressive tyranny was yet the seed-bed for an extraordinary flowering of the human spirit. It is difficult for either to remember that the forms which that flowering took and the imagery within which it found expression inevitably reflected the social and political conditions, the legal and judicial practices, familiar to those who gave it birth.