How does one decide what is inspired?

The only books about which there was any substantial doubt after the middle of the second century were some of those which come at the end of our New Testament. Origen (185-254) mentions the four Gospels, the Acts, the thirteen Paulines, 1 Peter, 1 John and Revelation as acknowledged by all; he says that Hebrews, 2 Peter, 2 and 3 John, James and Jude, with the 'Epistle of Barnabas,' the Shepherd of Hermas, the Didache, and the 'Gospel according to the Hebrews,' were disputed by some. Eusebius (c. 265-340) mentions as generally acknowledged all the books of our New Testament except James, Jude, 2 Peter, 2 and 3 John, which were disputed by some, but recognised by the majority. Athanasius in 367 lays down the twenty-seven books of our New Testament as alone canonical; shortly afterwards Jerome and Augustine followed his example in the West. The process farther east took a little longer; it was not until c. 508 that 2 Peter, 2 and 3 John, Jude and Revelation were included in a version of the Syriac Bible in addition to the other twenty two books.

For various reasons it was necessary for the Church to know exactly what books were divinely authoritative. The Gospels, recording 'all that Jesus began both to do and to teach,' could not be regarded as one whit lower in authority than the Old Testament books. And the teaching of the apostles in the Acts and Epistles was regarded as vested with His authority. It was natural, then, to accord to the apostolic writings of the new covenant the same degree of homage as was already paid to the prophetic writings of the old. Thus Justin Martyr, about AD 150, classes the 'Memoirs of the Apostles' along with the writings of the prophets, saving that both were read in meetings of Christians (Apol i. 67). For the Church did not, in spite of the breach with Judaism, repudiate the authority of the Old Testament; but, following the example of Christ and His apostles, received it as the Word of God. Indeed, so much did they make the Septuagint their own that, although it was originally a translation of the Hebrew Scriptures into Greek for Greek-speaking Jews before the time of Christ, the Jews left the Septuagint to the Christians, and a fresh Greek version of the Old Testament was made for Greek speaking Jews.

It was specially important to determine which books might be used for the establishment of Christian doctrine, and which might most confidently be appealed to in disputes with heretics. In particular, when Marcion drew up his canon about AD 140, it was necessary for the orthodox churches to know exactly what the true canon was, and this helped to speed up a process which had already begun. It is wrong, however, to talk or write as if the Church first began to draw up a canon after Marcion had published his.

Other circumstances which demanded clear definition of those books which possessed divine authority were the necessity of deciding which books should be read in church services (though certain books might be suitable for this purpose which could not be used to settle doctrinal questions), and the necessity of knowing which books might and might not be handed over on demand to the imperial police in times of persecution without incurring the guilt of sacrilege.

One thing must be emphatically stated. The New Testament books did not become authoritative for the Church because they were formally included in a canonical list; on the contrary, the Church included them in her canon because she already regarded them as divinely inspired, recognising their innate worth and general apostolic authority, direct or indirect. The first ecclesiastical councils to classify the canonical books were both held in North Africa — at Hippo Regius in 393 and at Carthage in 397 — but what these councils did was not to impose something new upon the Christian communities but to codify what was already the general practice of those communities.
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