I am at present reading Justinian’s Letter to the Monks of Alexandria Against the Monophysites. As I read, many questions arise: Did Justinian himself write this? When did he have time? Did he ever sleep? If he didn’t, who did? How was this text received? How would Leo the Great have felt about this text? What about Cyril of Alexandria?
Leo the Great (d. 461) would probably have been fine with this work. I am not sure Cyril (d. 444) would have been, however. This is an interesting reality of our theological tradition. Many people, even within the church, have an idea that theological orthodoxy is monolithic. It is not. Leo the Great did what he could with what of Cyril he had in Latin — not all of Cyril, and Latin is not Greek. So Leo’s Christology is not the same as Cyril’s.
For example, I do not think Leo’s Tome and Cyril’s On the Unity of Christ are actually perfectly compatible.
Yet Leo’s Tome was acclaimed and accepted at the Council of Chalcedon (that he helped engineer) in 451 on the grounds that it said what Cyril says. Which, if we consider the Cyril of the letter of reconciliation with John of Antioch Laetentur Caeli, I suppose it is. Both of these fifth-century bishops are accepted as authoritative by the imperial church and are regarded as Fathers of the Church by modern Roman Catholic, Eastern Orthodoxy, and non-heretical Protestant churches.
But their entire corpora are not entirely compatible, despite what Justinian tries in his reading of Cyril as a supporter of two-nature Christology.
Moving forward a couple of centuries, what about Maximus the Confessor (d. 662)? Again, I am not sure that the Cyril of On the Unity of Christ and some of Maximus’s arguments about the operation of Christ’s two wills in the Garden of Gethsemane are perfectly compatible.
Moving beyond christology, Augustine (d. 430), who is actually considered a saint by the eastern churches, teaches a dual procession of the Holy Spirit, that even Maximus agreed to in a way, although its offspring, the filioque in the creed, is a major point of division between the eastern and western churches. Yet here they stand, part of orthodox (note the lower-case O) tradition.
Gregory of Nyssa (d. 394) taught the Apocatastasis, the idea that all will be saved (patristic universalism). He is considered a Father in both East and West, although many reject this teaching. The ecumenically popular Isaac the Syrian (seventh century) also taught this.
Western accounts of the Most Holy and Undivided Trinity tend to start with the doctrine of God and His unity; in the East, they tend to start with the persons and the threeness. This is a generalisation, but it does tend towards a different feel and different emphases in our presentations of dogma. Yet these presentations, whether by Augustine or Gregory of Nazianzus (d. 390), are all orthodox though they differ.
Or consider the fact that our tradition includes alleged ‘Semi-Pelagians’ as saints (Faustus of Riez) alongside Augustinians like Prosper of Aquitaine.
Theological orthodoxy is not monolithic. Many other very specific cases could be found, but these will do. It is worth keeping these realities in mind as we ponder the great richness of the tradition that has brought us to where we stand today.