There are 3 basic tests that professionals use to determine the autheticity of an ancient document:
1. The Bibliographical Test
2. Internal Evidence Test
3. External Evidence Test
Test #1: The Bibliographical Test
What this test determines is the accuracy of the transmission of the text through time.To test the reliability of the New Testament, one would compare the copies available today to the original documents. There are two sides to this coin: how many supporting manuscripts are in existence, and what is the time interval between the original and the existing copies?
(A) Numbers of Supporting Manuscripts:
Greek Manuscripts 5,300
Latin Vulgate Manuscripts 10,000
Various Manuscripts 9,300
TOTAL 24,600
No other ancient document or book even compares to the New Testament in terms of numbers of supporting manuscripts! The 'Iliad' by Homer is the second competing ancient text with only 643 manuscripts compared to the tens of thousands (24,300) that support the New Testament. And, this does not exhaust manuscript sources. There are multiplied thousands of quotes from the Bible by all the early Church Fathers and also Lectionaries and Prayer Books full of Biblical passages.
Comparison of New Testament Manuscripts to other Ancient Text Manuscripts:
New Testament 24,300
Homer (Iliad) 643
Demosthenes 200
Plato (Tetralogies) 7
Caesar 10
Thucydides (History) 8
Herodotus (History) 8
Aristotle *49
Euripides 9
When comparing the number of manuscripts of ancient texts to that of the number of manuscripts of the New Testament, biblical scholars are almost embarrassed by the wealth of their materials that support the Bible.
(B) Time interval between the original and the existing copies:
Work When written Earliest copy Time span No. of copies
New Testament 40-100 A.D. 130 A.D. 30, 50, 100yrs* over 24,000
Homer (Iliad) 900 B.C. 400 B.C. 500 yrs 643
Demosthenes 383-322 B.C. 1100 A.D. 1,300 yrs 200
Plato (Tetralogies) 427-347 B.C. 900 A.D. 1,200 yrs 7
Caesar 100-44 B.C. 900 A.D. 1,000 yrs 10
Thucydides (History) 460-400 B.C. 900 A.D. 1,300 yrs 8
Herodotus (History) 480-425 B.C. 900 A.D. 1,300 yrs 8
Aristotle 384-322 B.C. 1100 A.D. 1,400 yrs 49
Euripides 480-406 B.C. 1100 A.D. 1,500 yrs 9
* John Rylands' Manuscript (130 A.D.), Bodmer Papyrus II (150-200 A.D.), Chester Beatty Papyri (200 A.D.) and many others, Codex Vaticanus (325-350 A.D.), Codex Sinaiticus (350 A.D.) Codex Alexandrinus (400 A.D.) etc...
In no other case is the time between the writing of the original document and the date of the earliest existing manuscript so short as in the case of the New Testament. No scholar of Ancient Texts would listen to an argument against the authenticity of Herodotus or Thucydides because the earliest existing manuscripts of their writings are over 1,300 older than the originals. Yet the New Testament is called into question continually by critics even though the earliest existing manuscripts are only a few decades or at worst a 100 years older than the originals.
A note about supposed errors in copying manuscripts:
Benjamin Warfield in 'Introduction to Textual Criticism of the New Testament,' says the facts show that the great majority of the New Testament "has been transmitted to us with no, or next to no, variation; and even in the most corrupt form in which it has ever appeared, to use the often quoted words of Richard Bentley, 'the real text of the sacred writers is competently exact;... nor is one article of faith or moral precept either perverted or lost, ... ' "
Sir Frederic Kenyon ( one of the great authorities in the field of New Testament textual criticism ) states, "One word of warning already referred to, must be emphasized in conclusion. No fundamental doctrine of the Christian faith rests on a disputed reading ... "
When accusations of textual errors are researched, one finds out that most of these have to do with trivial disputes. When one gets down to the small percentage of debatable differences, it becomes apparent that even in the worst case, no major doctrine of Christianity is in question. The "substance" on the New Testament is intact and reliable from the original writings!
He continues, "It cannot be too strongly asserted that in substance the text of the Bible is certain: Especially is this the case with the New Testament. The number of manuscripts of the New Testament, of early translations from it, and of quotations from it in the oldest writers of the Church, is so large that it is practically certain that the true reading of every doubtful passage is preserved in someone or other of these ancient authorities. This can be said of no other ancient book in the world."
Regarding his second point, Kenyon comments on the fact that another huge source of supporting manuscripts for the New Testament come from the early church fathers as they quote parts of scripture in their letters and books.
--> Ignatius ( A.D. 70-110) was Bishop of Antioch, knew the apostles well, and had quotations from 13 of the epistles.
--> Clement of Alexandria (A.D. 150-212) had 2,400 quotations from all but 3 of the New Testament books.
--> Tertullian (A.D. 160-220) quotes more than 7,000 times from the New Testament, of which 3,800 are from the Gospels.
--> Hippolytus, Justin Martyr, Origen etc... are also included as quoting from the New Testament extensively.
--> J. Harlod Greenlee says that the quotations of the Scripture in the works of the early Christian writers ' are so extensive that the New Testament could virtually be reconstructed from them without the use of New Testament manuscripts.' "
Another very significant source of New Testament quotations come from the Lectionaries of the early church. These are books, like the Book of Common Prayer in the Episcopal Church, contains portions of scripture that are arranged in some order so that the church members may read sections of the bible daily throughout the year.