If we want to know what Christianity looked like immediately after the age of the apostles, speculation is unnecessary. A small but important body of Christian literature survives from the late first and second centuries: 1 Clement, the Didache, the letters of Ignatius of Antioch, the writings of Justin Martyr, and Irenaeus of Lyons, among others.
These texts do not answer every question modern Christians ask. They also should not be forced into later denominational categories. But they do allow us to identify several features of early Christianity with unusual clarity.
1. The earliest Christians were intensely centered on Jesus Christ
The earliest post-New Testament writers did not treat Jesus as merely an ethical teacher.
Ignatius of Antioch, writing in the early second century, repeatedly speaks of Jesus in divine terms while simultaneously insisting that He truly became human, truly suffered, and truly rose. His concern was partly anti-Docetic: some teachers claimed that Christ only appeared to possess flesh or suffer. Ignatius opposed that idea because the incarnation, crucifixion, and resurrection were central to salvation.
This matters historically. High claims about Christ are not a late medieval development. They are already present in Paul and the New Testament, and they remain prominent in the generation immediately following the apostles.
At the same time, early Christian language about the Trinity was not yet expressed with the technical precision that would emerge in the fourth century. The Nicene term homoousios and the later creedal formulas were developments in vocabulary used to defend convictions that Christians believed were already embedded in Scripture and worship.
2. Baptism was treated as more than a public symbol
The Didache, an early Christian church manual whose final form is commonly placed in the late first or early second century, gives practical instructions for baptism. It prefers baptism in flowing water but allows other forms when necessary, showing both a defined rite and pastoral flexibility.
Justin Martyr, writing in the middle of the second century, describes converts being brought to water and receiving a washing associated with regeneration and forgiveness. Whatever differences later Christians have over baptismal theology, the earliest post-apostolic evidence does not portray baptism as an optional piece of religious theater.
The New Testament itself provides the background: baptism is linked with repentance, incorporation into Christ, forgiveness, new life, and entry into the Christian community (Acts 2:38; Romans 6:3–4; Galatians 3:27; 1 Peter 3:21).
3. The Eucharist occupied the center of Christian worship
The evidence here is especially strong.
The Didache contains Eucharistic prayers and restricts participation to the baptized. Ignatius calls the Eucharist the flesh of Jesus Christ while arguing against Docetic opponents. Justin Martyr says Christians did not receive the consecrated food as ordinary bread and drink, but as the flesh and blood of the incarnate Jesus. Irenaeus similarly speaks of the bread and cup as the body and blood of Christ and uses the Eucharist in his argument for the future resurrection of the body.
Modern Christians should still avoid anachronism. These writers do not explain the Eucharist using every philosophical distinction that would appear in later centuries. The word transubstantiation, for example, belongs to a much later Western theological vocabulary.
But the opposite exaggeration is equally unsustainable. It is difficult to read Ignatius, Justin, and Irenaeus as if they understood Communion to be only a mental recollection involving ordinary bread and wine.
4. Sunday was the normal day of Christian assembly
Justin gives one of the earliest detailed descriptions of Christian Sunday worship. Christians gathered, readings from the “memoirs of the apostles” and the prophets were proclaimed, the presider exhorted the congregation, prayers were offered, and bread, wine, and water were brought for the Eucharistic thanksgiving.
Justin explicitly connects Sunday with creation and the resurrection of Jesus.
This does not mean that every question about Sabbath observance disappeared immediately. Jewish-Christian communities and differing local customs continued to exist. But the evidence for distinctly Christian Sunday assembly is early and explicit.
5. Early Christianity had identifiable ordained leadership
The New Testament uses the terms episkopos (bishop/overseer) and presbyteros (elder/presbyter) in ways that can overlap. Historians therefore should not pretend that the fully developed structures of later centuries can simply be projected backward into every first-century congregation.
Even with that caution, the trajectory is unmistakable.
1 Clement says the apostles appointed bishops and deacons and made provision for ministry to continue after their deaths. The Didache instructs communities to appoint bishops and deacons. By the time of Ignatius, a threefold pattern of bishop, presbyters, and deacons is explicit in the churches to which he writes.
Irenaeus, later in the second century, appeals directly to public successions of bishops as a way of testing competing claims to apostolic teaching.
The evidence therefore supports continuity and development, not either extreme of “nothing changed” or “the institutional Church was invented centuries later.”
6. The Church was understood as a visible community, not merely an invisible collection of individuals
Early Christian writers cared intensely about unity.
Clement intervenes in a serious leadership dispute at Corinth. Ignatius repeatedly urges Christians to remain united with their bishop, presbytery, deacons, Eucharist, and local church. Irenaeus argues against Gnostic groups by pointing to the public teaching preserved in churches founded by or connected with the apostles.
That does not settle every later Catholic-Orthodox-Protestant argument about ecclesiology. It does show that visible Church order, sacramental communion, and continuity of teaching were important extraordinarily early.
7. Scripture was authoritative — but Scripture was read inside the Church's inherited faith
The earliest Christians constantly quote Israel's Scriptures and increasingly cite writings that would become the New Testament. Scripture clearly possesses unique authority.
Yet the same writers also speak about the teaching handed down from the apostles, the public faith of the churches, the ministry of bishops and presbyters, and the worshiping life of the Christian community.
This is important because modern debates often force the evidence into a false choice: Bible or Church, Scripture or Tradition. Early Christianity did not normally speak that way. Scripture was received, proclaimed, interpreted, and defended within an apostolic ecclesial community.
8. Moral transformation was considered essential to Christian life
The Didache begins with the “Two Ways,” contrasting the way of life with the way of death. Clement emphasizes humility, repentance, charity, obedience, and peace. Ignatius warns against division and false teaching. Justin defends Christians partly by pointing to the moral transformation expected of converts.
Early Christianity was not merely assent to a list of propositions. Faith was expected to produce repentance, holiness, generosity, fidelity, endurance, and communion with the Church.
So what did the earliest Christians look like?
By the middle of the second century, a recognizable pattern is already visible:
- belief in the God of Israel and in Jesus Christ as the incarnate, crucified, and risen Lord;
- baptism as the rite of Christian initiation;
- Eucharistic worship treated with profound realism and reverence;
- regular Sunday assembly;
- bishops, presbyters, and deacons in developing but increasingly clear forms;
- concern for apostolic continuity and unity;
- authoritative Scriptures read within the Church's received faith;
- and a demanding moral vision centered on repentance, holiness, charity, and martyr-like fidelity.
There were disputes. Terminology developed. Local practice was not perfectly uniform. Christians argued about the date of Pascha, the boundaries of the biblical canon, discipline after grave sin, and theological vocabulary.
But “development” is not the same thing as “invention.”
The surviving documents do not reveal Christianity disappearing after the apostles and reappearing centuries later as an unrelated religion. They show an identifiable Christian movement preserving the apostolic proclamation while working out its implications in changing historical circumstances.
That is the starting point any serious account of early Christianity has to explain.
Sources and further reading
- 1 Clement 42–44, New Advent — late first-century testimony on apostolic appointment and succession of ministers.
- Didache, New Advent — early instructions on baptism, Eucharist, fasting, and ministers.
- Ignatius, Letter to the Smyrnaeans, New Advent — bishop, Eucharist, incarnation, and Church unity.
- Justin Martyr, First Apology, New Advent — baptism and a detailed account of Sunday Eucharistic worship.
- Irenaeus, Against Heresies III.3–4, New Advent — apostolic tradition and succession.
- Irenaeus, Against Heresies V.2, New Advent — Eucharist and bodily resurrection.