In the fourth century a.d. poetry was practically extinct, and hymns to the gods were almost always written in prose. Julian's Fourth Oration is, according to the definition of the rhetorician Menander, a φυσικὸς ὕμνος, a hymn that describes the physical qualities of a god. Julian was an uncritical disciple of the later Neo-Platonic school, and apparently reproduces without any important modification the doctrines of its chief representative, the Syrian Iamblichus, with whom begins the decadence of Neo-Platonism as a philosophy. Oriental superstition took the place of the severe spiritualism of Plotinus and his followers, and a philosophy that had been from the first markedly religious, is now expounded by theurgists and the devotees of strange Oriental cults. It is Mithras the Persian sun-god, rather than Apollo, whom Julian identifies with his “intellectual god” Helios, and Apollo plays a minor part among his manifestations. Mithras worship, which Tertullian called “a Satanic plagiarism of Christianity,” because in certain of its rites it recalled the sacraments of the Christian church, first made its appearance among the Romans in the first century b.c.609 Less [pg 349] hospitably received at first than the cults of Isis and Serapis and the Great Mother of Pessinus, it gradually overpowered them and finally dominated the whole Roman Empire, though it was never welcomed by the Hellenes. For the Romans it supplied the ideals of purity, devotion and self-control which the other cults had lacked. The worshippers of Mithras were taught to contend against the powers of evil, submitted themselves to a severe moral discipline, and their reward after death was to become as pure as the gods to whom they ascend. “If Christianity,” says Renan, “had been checked in its growth by some deadly disease, the world would have become Mithraic.” Julian, like the Emperor Commodus in the second century, had no doubt been initiated into the Mysteries of Mithras, and the severe discipline of the cult was profoundly attractive to one who had been estranged by early associations from the very similar teaching of the Christians.
Julian followed Plotinus and Iamblichus in making the supreme principle the One (ἓν) or the Good (τὸ ἀγαθὸν) which presides over the intelligible world (νοητὸς κόσμος), where rule Plato's Ideas, now called the intelligible gods (νοητοὶ θεοί). Iamblichus had imported into the Neo-Platonic system the intermediary world of intellectual gods (νοεροὶ θεοί). On them Helios-Mithras, their supreme god and centre, bestows the intelligence and creative and unifying forces that he has received from his transcendental counterpart among the intelligible gods. The third member of the triad is the world of sense-perception governed by the sun, the visible counterpart of Helios. What distinguishes Julian's [pg 350] triad610 from other Neo-Platonic triads is this hierarchy of three suns in the three worlds: and further, the importance that he gives to the intermediary world, the abode of Helios-Mithras. He pays little attention to the remote intelligible world and devotes his exposition to Helios, the intellectual god, and the visible sun. Helios is the link that relates the three members of the triad. His “middleness” (μεσότης) is not only local: he is in every possible sense the mediator and unifier. μεσότης is the Aristotelian word for the “mean,” but there is no evidence that it was used with the active sense of mediation before Julian. A passage in Plutarch however seems to indicate that the “middleness” of the sun was a Persian doctrine: “The principle of good most nearly resembles light, and the principle of evil darkness, and between both is Mithras; therefore the Persians called Mithras the Mediator” (μεσίτης).611 Naville has pointed out the resemblance between the sun as mediator and the Christian Logos, which Julian may have had in mind. Julian's system results in a practically monotheistic worship of Helios, and here he probably parts company with Iamblichus.
But though deeply influenced by Mithraism, Julian was attempting to revive the pagan gods, and if he could not, in the fourth century, restore the ancient faith in the gods of Homer he nevertheless could not omit from his creed the numerous deities whose temples and altars he had rebuilt. Here he took advantage of the identification of Greek, [pg 351] Roman, and Oriental deities which had been going on for centuries. The old names, endeared by the associations of literature, could be retained without endangering the supremacy of Helios. Julian identifies Zeus, Helios, Hades, Oceanus and the Egyptian Serapis. But the omnipotent Zeus of Greek mythology is now a creative force which works with Helios and has no separate existence. Tradition had made Athene the child of Zeus, but Julian regards her as the manifestation of the intelligent forethought of Helios. Dionysus is the vehicle of his fairest thoughts, and Aphrodite a principle that emanates from him. He contrives that all the more important gods of Greece, Egypt and Persia shall play their parts as manifestations of Helios. The lesser gods are mediating demons as well as forces. His aim was to provide the Hellenic counterpart of the positive revealed religion of Christianity. Hence his insistence on the inspiration of Homer, Hesiod, and Plato, and his statement612 that the allegorical interpretations of the mysteries are not mere hypotheses, whereas the doctrines of the astronomers deserve no higher title.
The Oration is dedicated to his friend and comrade in arms Sallust who is probably identical with the Neo-Platonic philosopher, of the school of Iamblichus, who wrote about 360 the treatise On the Gods and the World. Cumont calls this “the official catechism of the Pagan empire,” and Wilamowitz regards it as the positive complement of Julian's pamphlet Against the Christians. Julian's Eighth Oration is a discourse of consolation, παραμυθητικὸς, for the departure of Sallust when Constantius recalled him from Gaul in 358.