We continue here with what the Muslim needs to know for understanding the formation of the Christian ‘canon‘  (the writings which were to become the New Testament) —as it relates to the story of shaping Christian ‘orthodoxy.’
Page numbers in this article refer to the Rubenstein book, When Jesus Became God, The Struggle to Define Christianity during the Last Days of Rome.
Authentic and Pseudo Writings, Connections, and Gaps
From a Muslim point of view, the four Gospel books of the New Testament (Matthew, Mark, Luke, and John) are best described as aHadith-like records of Prophet JesusAS. These Gospel writings do not themselves claim to be revealed words of God; be aware, however, that the doctrine held by many modern Christian groups claim this of them, and of the New Testament as a whole, quoting the writings of Paul where he refers to what at that time were the existing components of the Hebrew Bible:
…how from infancy you have known the Holy Writings, which are able to make you wise to salvation through faith in Christ Jesus; every Writing [is] God-breathed and profitable for teaching, for conviction, for setting aright, for instruction in righteousness—so that the godly man may be fully furnished for every good endeavor. (Second Letter of Paul to Timothy 3:15-17)
On the other hand, the Gospels recollect the story of Jesus’ ministry, who received prophetic teaching from God, finished the work that God had given him to do (John 17:4) and faithfully passed it on (John 14:9-11; 15:15b) to his followers. Twelve of them were designated to take his message to the worldwide (Matthew 28:19a) scattering of the descendants of Abraham – Isaac – Jacob (Matthew 10:5-7).
The New Testament is not a Christian equivalent to the Quran, which does claim to be a composition of divine words sent down from God.
Allah! There is no god but Him — the Living, the Self-subsisting, Eternal. It is He who sent down to you [step-by-step], in truth, the Book, confirming what went before it; and He sent down the Law [of Moses] and the Gospel [message of Jesus]. [Sûrah Âl CImrān, 3:2-3]
Similarly, the Acts of the Apostles forefront aHadith-like remembrances of events involving certain principal personally-mentored trainees of Jesus—Peter, James,  and John at the beginning. But other figures, notably Paul, occupied its later pages.
The documents approved by Church synod  had been judged to be of genuine Apostolic  provenance and thus were approved to be included in Christian Scripture. The Gospel of Matthew claimed to be linked to the authority of the Disciple of Jesus, Matthew,  the “Tax Collector”; the Gospel of Mark links with the chief Disciple, Peter, through his “interpreter” Mark,  according to the writings of Papias,  quoted by the 4th century Church historian Eusebius. 
The Gospel of John likely did not originate from John,  “the brother of James, son of Zebedee,” who was one of the Twelve Disciples: Scholarship has named several others as possible “John”  candidates for authorship. The Gospel of Luke—noticeably similar to the Gospel of Matthew in its stock of narrative incidents and its wordings—is not connectable to any Disciple known by the name “Luke”  ; the only identified person named Luke is one addressed in Paul’s letters as their “doctor,” travel companion, and co-worker (Colossians 4:14, 2 Timothy 4:11, Philemon 1:24).
In addition to those four accepted “Gospels” works, there were numerous other “gospels,” “acts,” “letters” purported to originate with the Apostles—and even further letters supposed to have come from Paul—that the Church declined to include, judging them spurious. Some of those bogus texts are still available to scholars today—such as the fragment of the Gnostic “Gospel of Peter,”  to name only one. While such writings falsely claim the authority of genuine Apostles, still they are of value to us in reflecting the various, competing philosophies of the day.
The only New Testament book actually claiming to be a writing (or “scroll” ) divinely revealed (actually, it claims to be revealed by “Jesus Christ” to “John”!) is the last one, the Revelation to John,  a visionary picture of persecution and assurance of the final victory of “Christ,” the sacrificial “Lamb of God”  —in accord with Paul’s theology. Other apocalyptic  books of visionary revelation existed at the time, but those, too, were excluded from the New Testament canon.
Writing Paul’s Christ into the Jesus Story
We see that the Church went through several centuries during which she debated just which of the available documents were to constitute the complete Christian scripture. Whether Paul is to be credited with single-handedly authoring the “Gospel of Jesus Christ,” which he prolifically expounds in a significant segment of the New Testament pages, perhaps only Allah now knows.
On the other hand, we do have abundant historical evidence—though not referred to by name in Paul’s work—of various metaphysical groups sporting a heavenly “Christ”-type figure, one come to “save” hapless humans from “the present evil age,” groups populated most notably by “Gnostics”  —a cover-term for numerous groups of multiple stripes– and still poorly understood by scholars.
Bible, Paul’s Letter to the Galatians 1:4 …in order to set us free from this present evil age, Christ gave himself for our sins, in obedience to the will of our God and Father.
Bible, Paul’s Letter to the Ephesians  1:19-21; 6:12 This power working within us is the same as the mighty strength which he used when he raised Christ from death and seated him at his right side in the heavenly world. Christ rules there above all heavenly rulers, authorities, powers, and lords; he has a title superior to all titles of authority in this world and in the next.
… For we are not fighting against human beings but against the wicked spiritual forces in the heavenly world, the rulers, authorities, and cosmic powers of this dark age.
There is a content gap between the 1st century of Prophet Jesus together with his Apostles fanning out from Jerusalem to the Jewish Diaspora, on the one hand, and Emperor Constantine with his 4th century official adoption of Pauline Christianity as the State Church, on the other hand. Except for some selective events in the first chapters of the Acts of the Apostles, the Twelve Disciples—the designated transmitters of Jesus’ message—are “missing in action” from the rest of our records. That void is filled with the writings of the “Church Fathers”  and Eusebius’ Church History . Unsurprisingly, these heroes of Christian faith and martyrdom held fast to Pauline interpretation, clinching the case—in the mind of the unsophisticated public—that they represented the teaching of Jesus.
Most depressing of all is the lack of complete manuscript copies of Gospel texts  dateable before the fourth century—although there are hundreds of earlier small fragments of various parts of the New Testament—and the paucity of transmission details regarding the four Gospel works.
How Did It All Play Out?
Our brief excursus finished, we are ready to return to Rubenstein’s novelesque retelling of the 4th century Arian versus Anti-Arian controversy, which continues for another hundred pages with the exploits of the two parties contending for orthodoxy. Church History details for us the criminal activity and accusations thereof, unscrupulous tricks and strong-armed bullying at Church Councils, condemnations and excommunications from Church membership, appeals to the Emperor to reverse Church decisions, trumped-up charges, insults, hostage holding, blackmail—all were part of the colorful, on-going political intrigue. (Rubenstein, pp. 119-134)
This was the background in which the Church forged Christian doctrine on the anvil of philosophical controversy.
This story, insha’ Allah, continues in Part 19…