Lucifer was Bishop of Cagliari in Sardinia in the middle of the fourth century. He was a devoted ally of the great theologian and Bishop of Alexandria, St Athanasius, and a strong opponent of Arianism and the Roman Emperor Constantius II. Exiled with Athanasius in AD 355 his surviving writings are all vituperative attacks on the emperor. The two books 'Concerning Athanasius' are his most substantial work, written in 359-360. Lucifer gives us a vivid picture of the passion aroused in the fourth century by debates about the nature of Christ and the relationship between the Church and the Roman Empire. This volume is the first translation into English of any of Lucifer's works.