Arnobius[a] (died c. 330) was an early Christian apologist of Berber origin, during the reign of Diocletian (284-305). According to Jerome's Chronicle, Arnobius, before his conversion, was a distinguished Numidian rhetorician at Sicca Veneria (El Kef, Tunisia), a major Christian center in Proconsular Africa, and owed his conversion to a premonitory dream. Arnobius writes dismissively of dreams in his surviving book, so perhaps Jerome was projecting his own respect for the content of dreams. According to Jerome, to overcome the doubts of the local bishop as to the earnestness of his Christian belief he wrote (c. 303, from evidence in IV:36) an apologetic work in seven books that St. Jerome calls Adversus gentes but which is entitled Adversus nationes in the only (9th-century) manuscript that has survived. Jerome's reference, his remark that Lactantius was a pupil of Arnobius and the surviving treatise are all that we know about Arnobius.
Adversus nationes (Against the Pagans) was composed in response to Diocletian's persecution of Christians, and was a rebuttal to Pagan arguments as to why the persecution was justifiable. Arnobius, "a practitioner of the coarse and turgid style that is called African", is a vigorous apologist for the Christian faith, more earnest in his defence of Christianity than perfectly orthodox in his tenets. His book has been occasioned by complaints that the Christians had brought the wrath of the gods on Ancient Rome. Thus, he holds the heathen gods to be real beings, but subordinate to the supreme Christian God; in a streak of gnosticism, he affirms that the human soul (Book II, 14 - 62) is not the work of God, but of an intermediate being, and is not immortal by nature, but capable of putting on immortality as a grace. He even says that a belief in the soul's immortality would tend to remove moral restraint, and have a prejudicial effect on human life. Never specifically identifying his pagan adversaries, some of whom may be straw men, set up to be demolished, Arnobius defends and expounds the rightness of monotheism and Christianity (deus princeps, deus summus) and the divinity of Christ, by adducing its rapid diffusion, its influence in civilizing barbarians and its consonance with the best philosophy. Christianizing Plato, he refutes pagan idolatry as filled with contradictions and openly immoral, and to demonstrate this point, his Books III through V abound with curious information gathered from reliable sources (e.g. Cornelius Labeo) concerning the forms of idolatrous worship, temples, idols, and the Graeco-Roman cult practice of his time, to the historian and mythographer's cautious delight, but all held up by Arnobius for Christian ridicule. Books VI and VII handle the questions of sacrifices and worship of images.
In book 2 section 4 of Adversus nationes, Arnobius gives the first known version of the argument later called Pascal's Wager, that in case of doubt about religion one should commit to it because of the rewards of doing so and risks of not doing so. He argues:
Since, then, the nature of the future is such that it cannot be grasped and comprehended by any anticipation, is it not more rational, of two things uncertain and hanging in doubtful suspense, rather to believe that which carries with it some hopes, than that which brings none at all? For in the one case there is no danger, if that which is said to be at hand should prove vain and groundless; in the other there is the greatest loss, even the loss of salvation, if, when the time has come, it be shown that there was nothing false in what was declared.
The work of Arnobius appears to have been written when he was a recent convert, for he does not possess a very extensive knowledge of Scripture. He knows nothing of the Old Testament, and only the life of Christ in the New, while he does not quote directly from the Gospels. He was much influenced by Lucretius and had read Plato. His statements concerning Greek and Roman mythology are based respectively on the Protrepticus of Clement of Alexandria, and on Cornelius Labeo, who belonged to the preceding generation and attempted to restore Neoplatonism.