How should we think about arguments regarding human authorship of certain passages or books of Scripture based on style and word choice? Here is an example of this argument against the authenticity of the Pericope Adulterae (John 7:53-8:11): “its writing style is very different from what we find in the rest of John (including the stories immediately before and after); and it includes a large number of words and phrases that are otherwise alien to the Gospel” (Bart Ehrman, Misquoting Jesus, p. 65).
The following six considerations will help us think through such arguments:
1) Mimicked Style
First, if a later scribe inserted a passage into the text of Scripture, why is it assumed that he is so incompetent at mimicking the original author’s style? As one scholar pointed out:
“The assumption behind arguments from style is that a later scribe would not have been able to mimic an earlier author’s style, and therefore that strong similarity suggests the same author. There is, however, no reason why an astute later scribe could not have copied an earlier style.” 
2) Sample Size and Confidence
How large a sample of one human author’s undisputed writings would be needed to compare a disputed passage with to give enough certainty that the passage is indeed not the style or within the vocabulary of that human author? How would one determine a confidence level to a judgment like that? It is just as likely that there is not enough material in Scripture to compare style and word choice of a disputed passage to, in a statistically significant way, because the human authors wrote too small of a sample. The whole endeavor may be of some value in secular fields, but is ultimately arbitrary and ignores the divine nature of God’s Word.
For example, regarding the Pericope Adulterae, “G. Udney Yule, a professional statistician and reader of statistics at the University of Cambridge, has shown that it takes at least 10,000 words to form any solid statistical basis for authorship. In John 7:53-8:11 there are only 174 words. The insufficiency is evident.” 
3) Authorial Intent
Sometimes when terms only appearing once in a book of the Bible (hapax legomenon) are more highly concentrated in one passage than average, it is considered evidence that that passage may not have been written by the traditional author. However, this is poor statistical analysis because it disregards the possible variation and assumes words are being randomly placed on the page. An author is going to use different words for different topics. This method “does not take into account the mood, purpose, and subject matter of the author.”  Again, using the Pericope Adulterae as an example:
“The Gospel According to John has 376 hapax legomena in a total of the 15,635 words in this book. The unaware could calculate that this comes to an average of one hapax legomenon for every 41.6 words, and that the Pericope Adulterae, which consists of 174 words, should therefore have only four hapax legomena, instead of the fourteen that it does have. The problem with this is that unlike, say, flipping coins, which is regular and has a limited number of possible outcomes, the choice of words a writer may use is vast and is dependent on subject matter, so whatever the average may be in such cases, the standard deviation is huge and finding three or four times the average number in a passage carries no significance at all.”
4) Arbitrary Application of the Method
Unique style and word choice can be argued from just about anywhere in Scripture, even from passages where the human author is not disputed. For example, many undisputed passages in John (6:3-14; 9:1-12; 4:5-16; 21:1-12; etc.) have been shown to have the same number of so-called “non-Johannine” words as the Pericope Adulterae.  Dr. Alan Johnson likewise has shown that this method would call into question the authenticity of John 2:13-17, which no one otherwise disputes .
Additionally, Dr. Gordon Fee points out that there are many passages with unique language which could be argued to be “non-Pauline.”
“e.g., 1 Thes 1:9-10; 5:9-10; 2 Thes 2:13-14; 1 Cor 5:7; 6:11; 6:20; 15:3-5; 2 Cor 5:18-21; 8-9; Gal 1:4; 4:4-6; Rom 3:23-25; 4:24-25; Col 1:15-20; 1:21-22; 2:11-15; Eph 1:3-14; Phil 3:8-11; 3:20-21; 1 Tim 1:15; 2:4-5; 3:16; Titus 2:11-14; 3:5-7; 2 Tim 1:9-10. One could easily show the “non-Pauline” character of all of these passages, since each of them has unique language and no two of them are alike. It is the very richness of these passages, and their obviously having been adapted to their contexts, that makes so much of the argumentation about the non-Pauline character of the present passage [Phil. 2:5-11] so tenuous.”
Philippians 2:5-11: Hymn or Exalted Pauline Prose?, Bulletin for Biblical Research (1992), footnote 43.
Consistent application of this method would require that we question the authenticity of a multitude of additional passages which would leave us with absurdity. Even when coupled with what some may consider stronger external evidence about the authenticity of a passage, a tenuous argument linked with a stronger argument doesn’t make the former less tenuous. If the stylistic differences wouldn’t normally be significant then they are still not significant just because additional arguments can be made. If it is a bad argument, the external data doesn’t somehow make it good. 
5) Final Canonical Form
The previous three considerations demonstrate the tenuous and arbitrary nature of proving that an objectively different writing style is present in many of these disputed passages, but even if we grant it, how does it prove that that passage is not authentic? It is the final canonical form of the text that we are concerned with. We’ve already seen, according to this standard, that the same author can have varying writing styles in the same short book, as well as use specific terms rarely or only once. What if the subject matter and purpose of the story of the woman caught in adultery is the reason John sounds different here? What if John, under the inspiration of the Holy Spirit, is relaying a well known oral story (c.f. John 21:25) largely word for word? 
It is perhaps less likely, yet still possible that the Holy Spirit used another 1st century hand in that particular place in the process of bringing the book to its final canonical form. This is the case with other portions of Scripture. For example, the reference to Dan in Gen. 14:14 has been thought by interpreters to be edited by Samuel or another inspired person to reflect what later Israelites called that region because Moses died before Dan was a territory. But examples like this must be held to be inspired and canonical because Jesus received the final form of the text of Moses as canonical. 
Stylistic and lexical arguments are the same sort made in extremely liberal arguments that conservative Christians would reject with regard to the JEDP hypothesis and other higher critical theories. Critical scholars can not even agree about what passages in the Pentateuch the alleged J, E, D, and P authors are represented. The impiety of disregarding Scripture’s testimony of itself, the unreliability of disregarding the universal Church’s witness to Scripture, and the arbitrariness of style and word choice as distinguishing factors is clearly seen in extreme higher critical theories, yet the same argumentation is accepted by conservative Christians with regard to other passages. It is inconsistent with our most fundamental doctrines. We must not let it creep into our beliefs elsewhere.
Ultimately this argument, along with other arguments against the authenticity of the story of the woman caught in adultery, is specious and gives us nowhere near the certainty required to remove this passage from holy Scripture. And again, if stylistic differences would not normally be significant then they do not suddenly become more probable just because additional arguments from manuscript evidence can be made.
 Chris Keith, The Initial Location of the Pericope Adulterae in Fourfold Tradition, Novum Testamentum 51, p. 211.
 Alan F. Johnson, A Stylistic Trait of the Fourth Gospel in the Pericope Adulterae?, Journal of the Evangelical Theological Society 9, p. 93.
 A.W. Wilson, The Adulteress and Her Accusers: A Study in Intrinsic Probability, A New Approach to NT textual criticism.
“Four possible reasons, then, based on statistics, could be advanced against the Johannine authorship of 2:13-17: (1) the large number of hapax words (14) not found elsewhere in John, (2) the use of frequent synoptic words rare in John, (3) the use of words more Lukan and Markan than Johannine, and (4) the absence proportionately of a sufficient number of Johannine preferred words and particles compared to other sections in the Fourth Gospel. To these could be added the abruptness of the incident in the context and the apparent historical anachronism of an early temple cleansing. It is hoped that by seeing how statistics can discredit a genuine passage in John, the obvious weakness of such a method will be acknowledged and abandoned by serious students who are searching for a true evaluation of the linguistic phenomena of 7:53-8:11.” (Alan, ibid., p. 94).
 However, we deny that the external evidence against the Pericope Adulterae is actually strong. See Why the Story of the Woman Caught in Adultery Belongs in the Bible as well as the links at the bottom of the page.
 Something similar (although against the authenticity of the PA) has been posited by a student of Dan Wallace: K.R. Hughes, The Lukan Special Material and the Tradition History of the Pericope Adulterae, Novum Testamentum 55, pp. 232-251.
Hughes’ article argues that the PA is likely a true story but originates from an “L Source” from “the middle of the first century” that is stylistically similar to Luke (that Luke likely knew of “and perhaps even reworked it“, “but chose not to include it” in his gospel) and was passed on by oral tradition, but inserted into John’s Gospel by scribes centuries later to prove that Jesus was educated enough to write.
 While some claim Moses was being prophetic here (c.f. John Gill), that is unlikely because this would have been incomprehensible to his original audience without some sort of explanation.