Christianity in the ante-Nicene period

Christianity in the ante-Nicene period was the period in Christian history following the Apostolic Age (1st century AD) up to the First Council of Nicaea (325 AD). Although the use of the term Christian (Koinē Greek: Χριστιανός) is attested in the Acts of the Apostles (80–90 AD), the earliest recorded use of the term Christianity (Koinē Greek: Χριστιανισμός) is attested by the ante-Nicene Father and theologian Ignatius of Antioch (c. 107 AD).

While the Jewish–Christian community was centered in Jerusalem in the 1st century AD, Gentile Christianity spread widely in the 2nd century AD. One stream of Gentile Christianity (so-called "proto-Orthodox Christianity") that emerged in this period in the persons and theological positions of the Apostolic Fathers would eventually become the international Great Church. Proto-Orthodox Christianity placed importance on the sacrifice of Jesus on the cross as saving humanity, and described Jesus as the incarnated Son of God come to Earth. The 2nd and 3rd centuries AD saw a sharp separation between Jewish Christianity and Gentile Christianity, with the latter being derived from the teachings of the Apostle Paul. There was an explicit rejection of Second Temple Judaism and Jewish culture by the end of the 2nd century, with a growing body of anti-Jewish Christian literature.

Many doctrinal variations in this era defy neat categorizations, as various forms of Christianity interacted in a complex fashion. Various local and provincial ancient Church councils were held during this period, with the decisions meeting varying degrees of acceptance by different Christian groups. Major Christian figures of the 2nd century who were later declared by the developing proto-Orthodox faction to be heretics were Marcion, Montanus, and Valentinus.

Another major school of thought was Gnostic Christianity, which regarded Jesus Christ as a divine being sent by a supreme, Unknown God who pre-existed and was superior to the Hebrew God of the Old Testament (actually the Demiurge or false creator of the material universe), and who brought salvation through direct, experiential "knowledge" (gnosis). In the 4th and 5th centuries AD, after centuries of intermittent persecution, proto-Orthodox Christianity experienced both pressure and recognition from the Roman State and developed a strong episcopal and unifying structure, leading to its legalization under the Emperor Constantine (313 AD).