When historians and students of ancient history wish to learn about the beliefs and practices of a particular culture or people group, where do they turn? The best method of research is to go back and let the ancient voices speak for themselves through the writings that have been left for us. How do we know what ancient Romans believed? How have we come to understand so much about their politics, beliefs and cultural mores? Through studying the writings of their politicians, philosophers and historians.

In a similar way, students of ancient Christianity learn about the beliefs and practices of the early Christians by reading materials written by the original historians, church leaders and theologians who lived during those New Testament times. The New Testament Scriptures were not given for the express purpose of being the only source of historical data for that time period. Therefore it is intellectually imperative to seek sources outside of Scripture to gain a better appreciation for how these early believers practiced the new culture of Christianity. Just because a historical source was not included in the canon by the Church in the fourth century does not rule out its usefulness in learning more about the practices of these first and second generation disciples. An example is the Creed written in 325 AD. Is it unimportant and not to be studied because it is not canonical? To get an idea of what the early Church believed would it really be appropriate to skip over the Creed in our research?

Regardless of our personnel 21st century theological beliefs, wouldn't we want to know if the new Church baptized infants? Did they use full immersion or sprinkle? What did the first generation of disciples believe was necessary to become a member of the first church? How did they celebrate the Lord's supper in 70 AD? The New Testament alone would not provide historical researchers everything they needed to know about the practices of this early group of believers since the New Testament was not given to us by God to be the sole source of early church history. As a matter of fact, most of the letters included in the New Testament were written with the intention to exhort, encourage or correct an abuse or budding heresy. So there exists the very real possibility that the writers of the New Testament did not set out to create an "Official Handbook of the First Christians."
To be sure these letters are recognized by the Church as the Word of God, but the writers didn't intend to spell out all that there was to know about the new church.

Analogous to Christianity, theologians of ancient Judaism do not limit their research to the books of the Old Testament alone to learn about Jewish religious and cultural practices. Would it therefore be academically honest for modern day researchers, theologians and Christian laymen (like myself) to limit their study of the early church to the New Testament alone?

Oftentimes, history is the best defense for Catholicism. Despite the attacks on sacramental theology, the writings of the early Church Fathers remain with us, and for some, pose An Inconvenient Truth. Though they are not canonical, they provide a snapshot of the early Christians' belief and practices which were unequivocally sacramental.

To quote myself :
"If sacramental theology is a 'man-made work' than you must assume the Church was "off the rails" even as early as the 2nd century. You must conclude therefore that Christ's promise that the Gates of Hell would not prevail only held true for the first generation of apostles before 70 AD.

Here are just a few of these "Inconvenient Truths"

Didache (Teachings of the Apostles) on the Eucharist

"Assemble on the Lord’s day, and break bread and offer the Eucharist; but first make confession of your faults, so that your sacrifice may be a pure one. Anyone who has a difference with his fellow is not to take part with you until he has been reconciled, so as to avoid any profanation of your sacrifice [Matt. 5:23–24]. For this is the offering of which the Lord has said, ‘Everywhere and always bring me a sacrifice that is undefiled, for I am a great king, says the Lord, and my name is the wonder of nations’ [Mal. 1:11, 14]" (Didache 14 [A.D. 70])

Ignatius of Antioch on the Sacrament of Holy Orders

"Indeed, when you submit to the bishop as you would to Jesus Christ, it is clear to me that you are living not in the manner of men but as Jesus Christ, who died for us, that through faith in his death you might escape dying. It is necessary, therefore—and such is your practice that you do nothing without the bishop, and that you be subject also to the presbytery, as to the apostles of Jesus Christ our hope, in whom we shall be found, if we live in him. It is necessary also that the deacons, the dispensers of the mysteries [sacraments] of Jesus Christ, be in every way pleasing to all men. For they are not the deacons of food and drink, but servants of the Church of God. They must therefore guard against blame as against fire" (Letter to the Trallians 2:1–3 [A.D. 110]).

St. John Chrysostom

"When you see the Lord immolated and lying upon the altar, and the priest bent over that sacrifice praying, and all the people empurpled by that precious blood, can you think that you are still among men and on earth? Or are you not lifted up to heaven?" (The Priesthood 3:4:177 [A.D. 387]).

St. Augustine on the Sacrament of Baptism and the Eucharist

"It is an excellent thing that the Punic [North African] Christians call baptism salvation and the sacrament of Christ’s body nothing else than life. Whence does this derive, except from an ancient and, as I suppose, apostolic tradition, by which the churches of Christ hold inherently that without baptism and participation at the table of the Lord it is impossible for any man to attain either to the kingdom of God or to salvation and life eternal? This is the witness of Scripture too" (Forgiveness and the Just Deserts of Sin, and the Baptism of Infants 1:24:34 [A.D. 412]).

Tertullian on the Sacraments of Baptism, Confirmation and Eucharist

"No soul whatever is able to obtain salvation unless it has believed while it was in the flesh. Indeed, the flesh is the hinge of salvation. . . . The flesh, then, is washed [baptism] so that the soul may be made clean. The flesh is anointed so that the soul may be dedicated to holiness. The flesh is signed so that the soul may be fortified. The flesh is shaded by the imposition of hands [confirmation] so that the soul may be illuminated by the Spirit. The flesh feeds on the body and blood of Christ [the Eucharist] so that the soul too may feed on God. They cannot, then, be separated in their reward, when they are united in their works" (The Resurrection of the Dead 8:2–3 [A.D. 210]).

Council of Carthage on Confirmation and Baptism [I]n the Gospel our Lord Jesus Christ spoke with his divine voice, saying, ‘Except a man be born again of water and the Spirit, he cannot enter the kingdom of God’ [John 3:5]. This is the Spirit which from the beginning was borne over the waters; for neither can the Spirit operate without the water, nor the water without the Spirit. Certain people therefore interpret [this passage] for themselves wrongly, when they say that by imposition of the hand they receive the Holy Ghost, and are thus received, when it is manifest that they ought to be born again [initiated] in the Catholic Church by both sacraments" (Seventh Carthage [A.D. 256]).

Tertullian on The Sacrament of Penance (Confession)
"[Regarding confession, some] flee from this work as being an exposure of themselves, or they put it off from day to day. I presume they are more mindful of modesty than of salvation, like those who contract a disease in the more shameful parts of the body and shun making themselves known to the physicians; and thus they perish along with their own bashfulness" (Repentance 10:1 [A.D. 203]).

Hippolytus on The Sacrament of Penance (Confession)

"[The bishop conducting the ordination of the new bishop shall pray:] God and Father of our Lord Jesus Christ. . . . Pour forth now that power which comes from you, from your royal Spirit, which you gave to your beloved Son, Jesus Christ, and which he bestowed upon his holy apostles . . . and grant this your servant, whom you have chosen for the episcopate, [the power] to feed your holy flock and to serve without blame as your high priest, ministering night and day to propitiate unceasingly before your face and to offer to you the gifts of your holy Church, and by the Spirit of the high priesthood to have the authority to forgive sins, in accord with your command" (Apostolic Tradition 3 [A.D. 215]).

Augustine on The Sacrament of Penance (Confession)
"When you shall have been baptized, keep to a good life in the commandments of God so that you may preserve your baptism to the very end. I do not tell you that you will live here without sin, but they are venial sins which this life is never without. Baptism was instituted for all sins. For light sins, without which we cannot live, prayer was instituted. . . . But do not commit those sins on account of which you would have to be separated from the body of Christ. Perish the thought! For those whom you see doing penance have committed crimes, either adultery or some other enormities. That is why they are doing penance. If their sins were light, daily prayer would suffice to blot them out. . . . In the Church, therefore, there are three ways in which sins are forgiven: in baptisms, in prayer, and in the greater humility of penance" (Sermon to Catechumens on the Creed 7:15, 8:16 [A.D. 395]).

Caesar of Arles (ca. A.D. 470-542) on the Sacrament of the Sick

"As often as some infirmity overtakes a man, let him who is ill receive the body and blood of Christ; let him humbly and in faith ask the presbyters for blessed oil, to anoint his body, so that what was written may be fulfilled in him: ‘Is anyone among you sick? Let him bring in the presbyters, and let them pray over him, anointing him with oil; and the prayer of faith will save the sick man, and the Lord will raise him up; and if he be in sins, they will be forgiven him. . . . See to it, brethren, that whoever is ill hasten to the church, both that he may receive health of body and will merit to obtain the forgiveness of his sins" (Sermons 13[325]:3).