The bibliographical, internal and external evidence tests confirm the following: that the books of Matthew, Mark, Luke, and John were composed by eyewitnesses on top of the events they record, that these works have a manuscript tradition that simply dwarfs any other works of antiquity, that they carry the evidence of internal consistency and personal attestation, and that they are supported by the soundest of external evidence from archeology.
— Craig Parton, from Religion on Trial, p. 60
[Authenticity] refers to the truth of the facts and content of the documents of the Bible. Authenticity deals with the integrity (trustworthiness) and credibility (truthfulness) of the record. A book may be genuine without being authentic, if the professed writer is the real one, even if the content is untrue. Then, again, a book may be authentic without being genuine, if the content is true but the professed writer is not the actual one. In such a case, the book would be called forged or spurious, regardless of the truthfulness or falsity of its content. Biblical books of course must be both genuine and authentic or they cannot be inspired, because in either case there would be a falsehood.
— Norman Geisler, from A General Introduction to the Bible, p. 343
You may choose at the end of your investigative process of the New Testament not to believe it, but you may not reserve the right to say ‘because there is not enough evidence to believe it’.
— Simon Greenleaf, famed law professor at Harvard