In the third century presbyters had acted at synods as spokesmen for the bishops; the council of Antioch laid it down as an axiom that bishops take the lead. As the bishop was above all the head of the worshipping congregation, creeds and liturgical practices were now regularly cited as ancillaries to biblical exegesis. At the same time, as the clergy gathered privileges and subsidies under Christian rule, their ranks were swelled by men who had received a professional schooling in philosophy and rhetoric. Eunomius, Bishop of Cyzicus, was (perhaps unfairly) decried as an Aristotelian when he reasoned that the Godhead contains two essences, since at least one attribute, that of being ingenerate (agennetos) is reserved for the Father alone. In reply the three Cappadocian Fathers (Basil of Caesarea, Gregory Nyssen, and Gregory Nazianzen) are at their strongest when they argue that whatever we predicate of the inscrutable Godhead is a feeble adumbration of its real properties, which cannot be unveiled in the present life. Even if, with Nyssen, we propose that the terms ‘‘begotten,’’ ‘‘unbegotten,’’ and ‘‘proceeding’’ denote relations rather than substances, we must refrain from inferring, as we would in any other instance, that beings who are related to one another cannot also be the same. A false desire for philosophical clarity lures both Basil and Nyssen into the assertion that the three hypostases are all God because they share divinity as an essence or ousia, just as any three men share the common essence of humanity. To forestall the charge of tritheism, Nyssen perversely argues in his Letter to Ablabius that an accurate use of words would allow us only to speak of ‘‘man’’ in the singular, never of a plurality of men. Perhaps he is taking for granted his own contention in The Making of Man that the image of God, as undivided intellect, resides identically in all human beings; to explain the peculiar logic of the term ‘‘God,’’ however, one needs, as Basil’s friend Apollinarius told him, to postulate not so much a generic as a ‘‘genarchic’’ unity, which consists in the descent of Son and Spirit from the Father, as men are united by their descent from David or from Adam (Basil, Ep. 362). It was in fact the Cappadocian Fathers who put the stamp of orthodoxy on this position, while the Second Oecumenical Council of 381 condemned the over-subtle Apollinarius for denying a human intellect to Christ.
The paradoxical union of God and man in Jesus became all the more perplexing with this settlement of the Trinitarian question, for the Cappadocians - unlike Origen, Arius, or even Athanasius - affirmed that the three hypostases were not only one in kind but fully equal in rank and power - as indeed they must be if they are all to be identical with the one God. If that is so, the Logos himself would share the impassibility of the Father, and could not have been the subject of the ignorance and weakness that are attributed to the Savior in the Gospels. On the other hand, if the man in Christ were merely a companion of the Logos, had the Word of God indeed become flesh, as John the Evangelist proclaimed? Apollinarius held that he inhabited a human body and soul in place of the intellect; Theodore of Mopsuestia and his ‘‘Antiochene’’ followers objected that in that case God himself would be a prisoner to the flesh. Nor could man be said to have overcome his own jailer, Satan, if the Logos were the sole agent of the victory; Nazianzen added that the human mind, not having been assumed in the incarnation, would not have been redeemed from its fallen state (Greg. Naz. Ep. 102). Cyril of Alexandria, however, thought (or at least affected to think) that his contemporary Nestorius, a follower of Theodore and Bishop of Constantinople, had posited so loose an association between the Logos and humanity as to make two Christs of one (Second Letter to Nestorius). At the Council of Ephesus in 431, Nestorius, who refused to confess that Mary was the mother of God, that the flesh of Christ was life-giving in the Eucharist, and that the Word of God had tasted death (Cyril, Ep. 3 anathemas 11 and 12), was deposed by a phalanx of Egyptian prelates. The partisans of Nestorius, led by Bishop John of Antioch, arrived too late and retaliated by deposing Cyril. An accord between John and Cyril, signed in 433, declared that Christ was consubstantial in his divinity with God and in his humanity with all other human beings. When a monk named Eutyches denied this, he was condemned by Flavian of Constantinople, but in 449, at the second Council of Ephesus, the Egyptian bishops carried the day against Flavian by force. At the instance of the emperor and the Bishop of Rome, an oecumenical council in 451 reversed this verdict and laid down that Christ existed in two natures, though he remained a single person or hypostasis; whatever we predicate of the man we predicate of the Logos, and conversely, though we do not say of him as man what we say of him as God.
There was little philosophy in these altercations, and in the west the career of Augustine illustrates the maxim that the one who makes the most of his education is the one who shows it least. In his youth he imbibed a material notion of God from the Manichaean heresy, which, because it taught that the spirit alone was worthy of redemption, made him tolerant of impurity in the flesh. He embraced philosophy as a moral discipline after reading the Hortensius of Cicero, and study of the Platonists reconciled him to catholic teaching on the incorporeality of God (Conf. 7 etc.). Augustine in his early prime was enough of a Neoplatonist to maintain, in his Soliloquies, that the soul must be immortal because it sees eternal objects, and to the end of his long life he remained indebted to Plotinus for the axiom that evil is a deficiency of being (though not, for Christians, a deficiency in matter). His literary mentor was the philosopher and rhetorician Marius Victorinus, a late convert to Christianity who had previously translated Plotinus and Porphyry into Latin. In his tracts against the Arians, Victorinus states that Father and Son are one because the former is everything in potentiality that the latter is in act. He also adapted the Neoplatonic doctrine that the mind is an ‘‘intelligible triad,’’ in which being, the proper object of cognition, takes the form of cognitive intellect through the medium of life. In the exposition of Victorinus, being corresponds to the Father, life and intellect (less consistently) to the Son and Spirit. Yet the mature Augustine, in his 15 books On the Trinity, takes only passing notice of the intelligible triad, grounding his vindication of divine unity on the Johannine dictum ‘‘God is love,’’ together with two psychological triads - mind, knowledge, love, and memory-understanding-will - which are dimly, if at all, anticipated in either Christian or pagan literature. These similes, drawn as they are from the incorporeal realm, have a clear advantage over those of Basil and Gregory Nyssen; and Augustine holds a stricter monotheism than any Platonist when he stipulates that the divine essentia is simply God (De Trin. 5.2.3).
Even less Platonic is the theory of divine predestination which was worked out against Pelagius and Celestius in the last two decades of Augustine’s life. Where they held that God has created humans with the ability to do good works and the freedom to reject or choose the Gospel, Augustine taught that Adam’s fall has rendered us incapable of exercising either faith or charity without divine assistance. Since God may will that his grace should be irresistible (and has so willed, according to the scriptures), it does not lie with the creature to accept or to refuse the offer: whoever is saved is saved by God alone (To Simplicianus, c.397 ce). So little does Pelagian freedom matter to Augustine that he conceives the final state of the elect as one in which sin has become impossible (City of God, Book 13 etc.); in this one tenet he is still a Platonist, who identifies freedom with the full possession of one’s nature, and deduces that an agent is not truly free so long as he can compromise his own nature by wrongdoing. A Platonist would not have said, however, that the righteous man is one who acts in charity, observes the rule of charity in interpreting the scriptures and cements the bond of charity by joining the Catholic Church. Platonists, says Augustine, are too proud to see the incarnate Word, and thus do not know what it is for Christ, the invisible fund of truth in every human intellect, to pour himself as sacrificial love into the soul.
Disputes over free will barely touched the east, where Pelagius was acquitted in 415. Nevertheless Celestius was condemned at Ephesus in 431, and Cyril intimates that the death of God was rendered necessary by the plight of Adam’s children. In the Christological debates that followed Chalcedon in 451, the question was rather ‘‘Whom do I worship?’’ than ‘‘How can I be saved?’’. In the last years of the fifth century this question was addressed by one who purports to be Paul’s convert Dionysius the Areopagite, though he gives himself away when he quotes passages from Proclus the Neoplatonist (again under a pseudonym) to extol the providential love of God. The treatise On the Divine Names and the Mystical Theology mark the climax in antiquity of the apophatic method which contends that the nature of God is better described by the negation than by the affirmation of properties. Whether his plagiarisms were intended to disguise the priority of the Neoplatonists or to hint that Christianity should befriend them, the first citation of Dionysius almost coincides with the famous edict of Justinian, which temporarily closed the schools of Athens. Although the Alexandrian school of Platonism survived for a generation, and even the Athenians came back, the expropriation of Greek culture was now complete, and from Justinian to the renaissance there was no academy of pagan thought outside the church.