I will not attempt to cover all the available material from the 100's A.D., but to review some of the better-known writings that show the special consideration in which the four canonical gospels were already held in that century. In this post I will briefly review the very early non-apostolic groups and Irenaeus' early attempts to show how we can know the genuine teachings received from the apostles.
Brief Notes on Non-Apostolic Christian Groups
Given that much interest is currently being paid to the views of Christians who were considered heretical and why they were considered heretical, it is worth taking a brief look at the writings these groups were using.
Interestingly, when reviewing the literature for and against alternate Christian groups that far back, their own writings and those who rebutted them recorded that they also typically used one or another of the same four gospels we now consider canonical. The Marcionites favored a version of Luke with many passages edited out for their particular theological reasons. The Gnostics favored the gospel according to John.
Irenaeus makes early mention (possibly the earliest mention) of a non-apostolic gospel called the Gospel of Truth, a writing which he disowned based on its late date and non-apostolic origins. He comments both that "they put forth their own compositions" in contrast with those received from the apostles, and "Indeed, they have arrived at such a pitch of audacity as to entitle their comparatively recent writing 'the Gospel of Truth'." (Against Heresies 3.11) Irenaeus also argues that this gospel "agrees in nothing with the Gospels of the Apostles", which is something of an overstatement despite the plain differences in focus and style. After a copy of the Gospel of Truth was recovered from Nag Hammadi and was available for direct examination, it seems to have the character of a devotional commentary on the apostolic Scriptures, done in a semi-mystical strain with Gnostic tendencies. From the standpoint of a historian looking at the life of Christ, the Gospel of Truth does not bear any direct witness to Christ, mentioning only what is already recorded in the received apostolic writings, and in ways which make clear it is referring to the earlier apostolic writings as the original source material. The Gospel of Truth likely dates to around 150 A.D.
Irenaeus on the Four Gospels
But what about the churches that were apostolic, that had been founded by the inner circle of Christ's own followers?
Irenaeus is one of the better-known Christian writers of the 100's A.D., an early leader in giving criteria for distinguishing true teaching from false. In this, he relied heavily on the witness of the apostles as passed on to his own day. He had in his time met Polycarp, bishop of the church in Smyrna who had personally known some of Christ's own apostles, including the apostle John. Irenaeus placed confidence in this recent and direct personal knowledge as a reliable chain of transmission, a guarantee that the teachings he had received in this church were authentic to what the apostles themselves had handed down. His comments on the gospels received by the apostolic churches are deservedly well-known:
Matthew published among the Hebrews a gospel in writing also in their own speech, while Peter and Paul were preaching the gospel and founding the church in Rome. After their death Mark in his turn, Peter's disciple and interpreter, delivered to us in writing the contents of Peter's preaching. Luke also, the follower of Paul, set down in a book the gospel preached by him. Then John, the disciple of the Lord, the one who leaned back on his bosom, gave forth his gospel while he was living at Ephesus in Asia. (Irenaeus, Against Heresies, 3.1.1Having briefly mentioned the origins of the four gospels and their apostolic origins (Matthew, Mark from Peter, Luke from Paul, and John), he later continues to explain how there are no other gospels recognized in the church except these four:
As there are four quarters of the world in whihc we live, and four universal winds, and as the church is dispersed over all the earth, and the gospel is the pillar and ground of the church, and the breath of life, so it is natural that it should have four pillars, breathing immorality from every quarter and kindling human life anew. Whence it is manifest that the Word, the architect of all things, who sits upon the cherubim and holds all things together, having been manifested to mankind, has given us the gospel in fourfold form, but held together by one Spirit. (He again names the gospels of Matthew, Mark, Luke, and John.) ... For the living creatures are quadriform, and the Gospel is quadriform, as is also the course followed by the Lord. ... these Gospels alone are true and reliable, and admit neither an increase nor diminution of the aforesaid number. (Irenaeus, Against Heresies, 3.11)
To be continued with more writings from the 100's A.D. ...