The textual critic... is a scholar who respects neither familiarity nor tradition insofar as texts and readings are concerned.
-- P. Kyle McCarter (Textual Criticism, Fortress Press, 1986, p. 11)
The tendency to make the Bible read what we want it to read is strong. Let's take an example: Matthew 19:24 (and parallels). The vast majority of texts read that it is easier for a camel to go through the eye of a needle than for a rich person to enter Heaven.
For Greek kamhlon, camel, however, a handful of authorities read kamilon, a rope.
The witnesses for this reading? In Matthew 19:24, they are 579, 1424, the Armenian, and a handful of lectionaries. In Mark 10:25, the list is family 13, 28, 579, and the Georgian version. In Luke 18:25, the list is S, family 13, 180, 579vid, 1010, 1424, and the Armenian and Georgian. Streeter would perhaps call this reading "Cæsarean." But surely we would recognize it as simply an error -- either an itacism or a clarification.
And yet, I recently had someone tell me that she had heard this reading was original. This is, be it noted, a modern who was hearing it from someone who claimed knowledge of the text.
I've also heard this reading explained in terms of the "eye of a needle" being a very narrow entry into Jerusalem. The clear tendency seems to be to try to explain away this reading: It's tricky for the rich to get in, but There Are Ways.
No doubt there are, on the principle that "all things are possible with God." But modifying the text to make it easier is surely an example of theological bias -- and surely to be avoided.
Theology has affected textual criticism for a very long time. Origen, in doing his textual work, adopted readings which he felt Christianity required. So, for instance, he rejected the reading "Jesus Barabbas" in Matthew 27:16-17 because he didn't believe the name Jesus could be applied to evildoers.
An even more extreme instance is shown by Justin Martyr, who quoted the first line of Psalm 95:10 LXX (=96:10 Hebrew) as "the Lord reigned FROM THE TREE." The key words "from the tree" do not appear in the Hebrew, nor in our major LXX manuscripts. But Justin accused the Jews of mutilating this verse, because it was so useful to his theological understanding. There is no question at this point; these words are not original. But theology led Justin to claim that they were.
More recently, we have seen various sects claim divine inspiration for their particular translations, rather than seeking the original text. The Catholic church long canonized the Clementine Vulgate; perhaps even more absurdly, there are many fundamentalist sects in the United States which give direct adherence to the The King James Bible. This may not seem like a theological issue, but it is: "God spoke to us, using this version."
To what extent should theology affect textual criticism? This is a truly complex question, which has been answered in several ways. (It doesn't help that some who have followed their theological opinions have concealed it under the guise of following the author's style or the like.)
To demonstrate how important all this could be, consider the Longer Ending of Mark. This passage contains (16:16) the only NT passage explicitly linking baptism with salvation. All others refer to baptism as a cleansing of sins or the equivalent -- obviously worthwhile and desirable, and a token of membership of the church, but not a requirement for salvation. Does it not follow that, if critics allow theology to influence their criticism, then those who consider baptism important (e.g. Baptists) will tend to include the ending of Mark, while those who consider baptism less important (e.g. Quakers) would be inclined to omit it?
There are also historical implications. Consider the issue of whether Jesus was crucified on Passover or Passover Eve. On one side, we have the date in John. On the other, we have the date of the Synoptic Gospels, which essentially means the tradition of Mark. One witness on each side. Except that there is a single passage in Luke which may come from his special tradition: Luke 22:16. The Byzantine tradition has a reading which implicitly supports the Markan date; the Alexandrian tradition implies the Johannine date. A particular bias might lead one to support one or the other reading on non-textual grounds.
One group of textual workers (I hesitate to call them scholars) base their whole method on theology. These are the Providential Preservationists. So, for instance, Wilbur N. Pickering, "I believe that God has providentially preserved the original wording of the text down to our day... I see in the Traditional Text ('Byzantine') both the result and the proof of that preservation" (The Identity of the New Testament Text, First Edition, 1977, pp. 143-144.)
But, as Harry Sturz notes in reacting to Hills (another exponent of this doctrine), "Hills fails to show why the sovereign God must act in a particular way" (Harry A. Sturz, The Byzantine Text-Type & New Testament Textual Criticism, 1984, p. 42. Italics added.) Even if one accepts Providential Preservation, one must admit that it is arguing from theology back to the text, rather than from the text to theology.
It's also worth asking why Providential Preservation would preserve a text-type, as opposed to an actual text. If God were trying to preserve the Biblical text, would not God have given us one manuscript which is absolutely correct? Yet the Byzantine manuscripts do not agree entirely. How does one decide which manuscript has the exact text? Might it not as easily be B, or 1739, or 33, as opposed to K or 861 or whatever manuscript contains the Byzantine standard? And if God is going to hit us over the head with such a patent giveaway as preserving the exact text of the New Testament, wouldn't God also offer a few other obvious tokens of existence, such as would be available to ordinary people who didn't read Greek? (It will be evident that I consider Providential Preservation not only false but quite insulting.)
Not all who believe theology has a place in criticism go to this extreme. Most would, in fact, be angered by comparison to a Providential Preservationist. Most consider the manuscripts involved, the context, the nature of the variant, etc. (Note: This is not the same as considering the author's theology. Knowing the author's theology is obviously a tool for evaluating internal evidence. But that's not the same as considering the critic's own theology.)
I will admit, at this point, that I get lost. How can one consider theology in assessing a variant reading? You're telling God what God should have written! If one takes the Protestant view that the Bible is the determiner of faith, then you are applying an ex post facto judgment: The text should be telling you what to believe; you should not tell it. And even if one takes a Catholic/Orthodox view, with stress on church tradition, does not the fact that tradition has a place mean that the Bible is not a complete and perfect repository of the truth? This implies that it could have readings with false theological implications -- meaning that the original reading might not be "theologically correct."
Since I cannot understand the viewpoint of the theological critics, I will not attempt to take this point further. I will simply make the observation that a scientific criticism must necessarily reject any theological approach. But we should note that there has never been a scientific New Testament textual critic. Some have used mathematical methods -- but as tools, not final arbiters.
A quote from A. J. Ayer is relevant here, though not directed at textual criticism: "A man can always maintain his convictions in the face of apparently hostile evidence if he is prepared to make the necessary ad hoc assumptions. But although any particular instance in which a cherished hypothesis appears to be refuted can always be explained away, there must still remain the possibility that the hypothesis will ultimately be abandoned. Otherwise it is not a genuine hypothesis. For a proposition whose validity we are resolved to maintain in the face of any experience is not a hypothesis at all, but a definition" (Language, Truth, and Logic, p. 95).
I'll make one more appeal to logic. Several people have told me that they feel we must consider theology in editing the text. Some have, in fact, told me that I will be damned for not following their version of the New Testament text. Unlike them, I am not willing to pass such judgments. (I might be willing to allow that they are fools, but folly is surely not sufficient reason for damnation, else Hell is going to be very crowded indeed!) But I am willing to say that I would never trust a New Testament such a person edited. And they would never trust a New Testament I edited according to my theological principles. Is it not better to edit without reference to such principles, which would result in every editor producing a different New Testament? It might be different if somehow we all agreed on our theology. But we don't (and if we did, what need for the Bible anyway?).
Or try it another way: Would you want me, with my theological principles, editing the Bible according to my theology? If no, then why should anyone else want you to edit it according to your principles? There is an ancient name for this: It's called "heresy."