A couple weeks ago, I linked to an interview with Dan Wallace on the basics of textual criticism. So now as an illustration, here’s Wallace with an example of how textual critics work through the internal clues in the text and external clues in the manuscripts (considering their dates, geographical distribution, genealogy, etc.) to determine which wording is likely the original reading. The basic principle is, “choose the reading that best explains the rise of the others.”
The variant in question in this video is a bit of poor grammar found in Revelation 1:4 that appears in some manuscripts. Is it original? The answer Wallace comes to sheds light on the whole book of Revelation:
You can also see how Wallace resolves the tension between the opposing internal and external evidence for the variant in Matthew 27:16-17, or watch the whole series of these videos on “The Basics of New Testament Textual Criticism” from the Center for the Study of New Testament Manuscripts (CSNTM) on iTunes U.