The Romano-British writer Gildas, and thus by extension the Anglo-Saxon historian Bede (who uses Gildas as a source for earlier sections of his Historia Ecclesiastica), frame the decline of Rome within the Christian moral framework which underpins all of their writings.

While Gildas keeps an extensive list of the symptoms of Roman collapse - raiding, plagues, desolation, flight from the cities etc., the cause is framed as a moral issue. Namely the collapse of the empire is divine retribution for the sinfulness, complacency and profligacy of the Romans: Gildas makes much of the sexual debauchery of the Romans, the failure of the Romano-British leaders to provide just and fair leadership to their people and wider moral failing.