History of Christian theology

The doctrine of the Trinity, considered the core of Christian theology by Trinitarians, is the result of continuous exploration by the church of the biblical data, thrashed out in debate and treatises, eventually formulated at the First Council of Nicaea in AD 325 in a way they believe is consistent with the biblical witness, and further refined in later councils and writings. The most widely recognized Biblical foundations for the doctrine's formulation are in the Gospel of John.

Nontrinitarianism is any of several Christian beliefs that reject the Trinitarian doctrine that God is three distinct persons in one being. Modern nontrinitarian groups views differ widely on the nature of God, Jesus, and the Holy Spirit.

The Biblical canon is the set of books Christians regard as divinely inspired and thus constituting the Christian Bible. Though the early church used the Old Testament according to the canon of the Septuagint (LXX), the apostles did not otherwise leave a defined set of new scriptures; instead the New Testament developed over time.

The writings attributed to the apostles circulated amongst the earliest Christian communities. The Pauline epistles were circulating in collected form by the end of the 1st century AD. Justin Martyr, in the early 2nd century, mentions the "memoirs of the apostles", but his references are not detailed. Around 160 Irenaeus of Lyons argued for only four Gospels (the Tetramorph), and argued that it would be illogical to reject Acts of the Apostles but accept the Gospel of Luke, as both were from the same author. By the early 200's, Origen may have been using the same 27 books as in the modern New Testament, though there were still disputes over the canonicity of Hebrews, James, II Peter, II and III John, and Revelation, see Antilegomena. Likewise by 200 the Muratorian fragment shows that there existed a set of Christian writings somewhat similar to what is now the 27-book New Testament.

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