For the sake of concision, here follows an abbreviated account of the principal types of pre-Nicene Christianity. There were dozens, but we will deal with only the most important variations we know about :
• Primitive Jerusalem Christianity: no records; fresh, mysterious, simple; its message, the kerygma—God has acted again in history, the final age has begun in the ministry, death, and resurrection of Jesus; history will close upon his imminent return; visions, ecstasy; Jesus seen more as messiah than divine being; amorphous organization around the apostles.
• Primitive gentile Christianity: the concept of messiah means nothing; the gentile church had no eschatological background for Jesus; Jesus is son of God (raises questions about Jesus’ relation to God the Father); Jesus is Lord (therefore present now, not postponed to a second coming); Jesus the son of God came to earth, died, was resurrected and restored, is now Lord and present to his worshippers; rejection of Torah.
• Pauline Christianity: what we learn in Paul’s writings and those attributed to him; Paul knew primitive Jerusalem Christians but went to the gentiles; the gospel is universal; the gospel is about God’s grace (salvation granted to the unworthy); accepted messianic eschatology, the end coming soon—but not a paramount concern; rejected exclusivity for inclusivity; sin is real, the Mosaic law makes us aware of it, we invariably violate it, no human way out, leads to death; Christ supersedes the law, is condemned by the law but vindicated by God in the resurrection, power of sin broken; life in Christ produces what the law cannot but with few hard and fast ethical rules; love, not law: little interest in Jesus’ life, emphasis on him as Second Adam, something new, “in the form of God” became man and died, God raised him and made him Lord; justification, reconciliation, redemption, grace; church is those who wait for Jesus and live in Christ; initiation in baptism, sustenance in the eucharist.
• Johannine Christianity: what we learn from his gospel and letters; Jesus’ life secondary to his relation to the Father and the divine nature of Christ; truth about God exists independently of history, so Jesus is more revealer of God than actor in history; introduces Greek concept of logos, that which makes God’s being intelligible to humanity; the preexistent divine logos is incarnated in Jesus, and both are now present in history (via the Holy Spirit, the paraclete) and eternity; history is a medium of revelation; judgment is now; life in Christ resembles Paul’s but more mystical, sacramental understanding (Cana/water/wine; Nicodemus/born again; feeding/bread of life); all guaranteed by the paraclete, “only spirit gives life, flesh is no avail”; skirts gnosticism (see below) but seeks to communicate Jesus’ significance to the wider Greek culture.
• Jewish Christianity: various records; outgrowth of primitive form, led by James and successors (Jesus’ family), hounded in and out of Jerusalem, none there by A.D.135; a continuation of Judaism, Jesus is messiah in succession to the prophets, not divine, not virgin born, will be Messiah/Son of Man at return; rejected temple ritual but retained much of Torah and OT; an ethnic religion; they loathed Paul.
• Gnostic Christianity: gnosticism antedates Christianity, has roots all over the place and a vast literature; gnosis = special knowledge, the peephole in the curtain between us and Ultimate Reality, revealed through cult initiation; proceeds from a kind of free-floating, non-specific sense of unhappiness with life as it is; strongly anti-Semitic; apocalyptic; emphasized dualism, the struggle between good and evil, creation mostly evil; posits a vast structure of spiritual beings connecting God to us; body and soul are prisons for spirit; deliverance through a divine messenger; Jesus is docetic, an envelope for pure spirit; rejects the world, embraces asceticism; short on concrete terms, relies heavily on myths; the world is not redeemed but rather escaped; tremendously appealing in its humanity, it garnered many adherents.
Except for purely Jewish Christianity, all the above varieties and more were up and running concurrently—and adherents of all called themselves Christians—about the time the woman who became St. Helena went to Palestine and brought back what she promised were relics of the cross Jesus died on. Her son Constantine was running the eastern half of the Roman Empire. Raised a pagan, he converted famously to Christianity and was busy raising it to the status of state religion. But which kind? He gave the various church parties an ultimatum: clean up your act and give me a church that knows what it believes, an instrument of unity and centralization instead of the morass of claim and counter-claim and diversity and uncertainty I see now. So the church did what it always does: it held conventions—or councils or synods as they called them—meetings where people met and argued and voted.
Constantine forced an issue that had troubled the church for a long time, namely that Jesus had not returned to gather in the faithful, and that meant Christians had either to abandon that part of their faith or expand their understanding of Jesus’ gospel to encompass the possibility of a long and undefined future. The first choice was not a choice, so the church had to think: if the Second Coming, the parousia, is delayed or not what we think it is, then how are we to live in history? The councils Constantine set in motion undertook that monumental task. Working with the scriptures—some of which did not get into the Bible, by the way—and the work of people like Clement, Ignatius, Irenaeus, and the other Church Fathers, they started knocking the edges off loose definitions. They excluded the gnostics as too gauzy, the Jews as too picayune and tied to the past. The purely secular need to achieve a degree of unity sufficient to guarantee the church’s survival drove them: there were plenty of applicants for the job Constantine had in mind for the Christians. And it paid off. The Nicene/Chalcedonian formula presented a Christianity erected on four bases: the creeds, the sacraments, the apostolic succession, and the scriptures, all defined by those councils—for the moment.
And a splendid formulation it was and is, still accepted by the majority of Christians today, though by no means all. At least part of its long success is due to the way it excludes and assimilates, rejects the outworn or the bizarre and accepts much that was then new and risky, closes the door on small certainties and opens it to the nudging of the Holy Spirit. Classic catholic Christianity
• accepts Judaism’s insistence on the importance of history but rejects its obsession with ethnic identity;
• accepts the gnostic yearning for salvation but rejects its grotesque mythical claptrap;
• accepts the eschatological hope of eternal life in the Kingdom of God but rejects historical eschatology, a cataclysmic close of history at a predetermined moment;
• accepts ethical freedom in the context of Pauline love but rejects the demands of the Torah and other hyper-detailed moral codes;
• accepts John’s Christology and sacramentalism, the belief that God’s incarnation in Jesus expands in history, and rejects the docetist view that history doesn’t really count.
The formula has worked well because it preserves what is essential, lays aside what is not, and remains open to the possibility of adjustment to accommodate undeniable historical circumstance—and to the leading of the Holy Spirit. Constantine’s insistence got good results.