Now that we have taken stock of the fundamentally tenuous character of the inference to more than one source, let us briefly consider all that is built upon this foundation.
First, there is the question as to how these fragments were put together into a single literary work, say, the Individual Books of the Law (or the whole set) or a given Prophet or a given Psalm or a given Gospel. (Or is any of these a single work?) This question is the impetus for “Redaction Criticism.” Presupposing that there are various sources of the final text, the redaction critic asks various questions concerning why and in what ways they were put together into one document. Second, there is the question of dating. Which source is dated when? Also, when was the final product put together? Third, on the basis of these two inquiries, there is influence on how to interpret the final document. This issue I wish to stress presently.
Recall that the genesis of the inference that there are diverse sources is that there are contradictory affirmations in the final text. Well then, are there contradictions in the final text? Many historical critics say so. Take the following citation from the International Biblical Commentary as example:
The OT gives us three substantially irreconcilable insights into creation (one: Gen 1:1–2:4a; two: Gen 2:4b–25; three: Isa 51:9–10; Job 7:12; 9:13; 26:12–13; Ps 74:12–17 etc., these last involving mythic combat)…. We might say that in principle there is hardly a faith position taken in the OT that is not open to the possibility of being contradicted by another faith position that might equally be taken in the OT.
Ouch. Ouch. The first and second creation accounts contradict each other. Further, (though this involves two human authors), Genesis and Isaiah contradict each other. Again I say, Ouch.
Recall that the original presupposition was that the same man cannot affirm contradictions. Somehow, the redactor does not fall into this presupposition. Perhaps he lost his mind. Or perhaps the ancient religion didn’t really care about truth. Or perhaps truth is just the battle of antitheses, which balance each other out. Or perhaps there really isn’t much content in the bible. We are only invited to offer our own opinions. We are only given the subjective impressions of authors. These are some of the various outs suggested to explain the mindlessness affirmed by the redactor.
Now, how does the original observation and the final conclusion – that there are fundamental contradictions in this text and that – square with the faith? The 5th Lateran Council declares:
“And since truth cannot contradict truth, we define that every statement contrary to the enlightened truth of the faith is totally false and we strictly forbid teaching otherwise to be permitted.”
Here, the Church condemns every claim from reason that contradicts revelation. But God forbid the Church permit that revelation can contradict revelation. No indeed. In fact, the first clause excludes that: Truth cannot contradict truth. Therefore, no two affirmations in Scripture can contradict each other.
Pope Leo XIII underscores this:
“Let them loyally hold that God, the Creator and Ruler of all things, is also the Author of the Scriptures – and that therefore nothing can be proved either by physical science or archaeology which can really contradict the Scriptures. If, then, apparent contradiction be met with, every effort should be made to remove it. Judicious theologians and commentators should be consulted as to what is the true or most probable meaning of the passage in discussion, and the hostile arguments should be carefully weighed. Even if the difficulty is after all not cleared up and the discrepancy seems to remain, the contest must not be abandoned; truth cannot contradict truth, and we may be sure that some mistake has been made either in the interpretation of the sacred words, or in the polemical discussion itself; and if no such mistake can be detected, we must then suspend judgment for the time being” (Providentissimus Deus).
 Antony Campbell and Mark O’Brien, “1–2 Samuel,” in IBC, p. 576a (italics mine).