Not two this time, but three: Gen. 12:10-20, 20:1-18, and 26:1-11. These narratives, each detailing a man protecting his wife by calling her his sister, are frequently cited by JEDP theorists. The assignment of Gen. 20 to E and the other two stories to J highlights an inconsistency among some critical approaches, as they admit a doublet within the same author or else posit a series of 'J' sources to retain the theory.

The similarity of these stories, far from being proof of someone weaving together different sources, actually proves no such thing in the context of ancient literature. The use of repetition was par for the course in these contexts, and there is no reason why a single author cannot have been responsible for all three stories. One may as well posit varying authorship for the three accounts of Paul's conversion in Acts, yet Christianity broadly recognizes a single author for Acts without suggesting that Luke merely pieced together disparate historical-traditional sources.

Beyond that, there are certain discernible patterns explained far better by the premise of a single author than by a redactor(s) piecing together once-separate works. Garrett notes within the triad "a pattern in which a narrative element is consistently present in two out of the three accounts".

Many writers attempt to break up the stories in terms of motifs -- this we can certainly accept, especially under the reasonable assumption that being a wandering chieftain with a beautiful wife, and being forced by circumstances into more civilized areas, necessarily required some kind of 'she's-my-sister' deception in order to survive. Perhaps the reason the motifs evolved is because they reflected a hard reality.

Practically speaking, Hoffmeier argues convincingly that a sort of "diplomatic marriage" custom lies behind all three stories: In order to gain the protection of the king, along with water and grazing rights, the patriarchs, having no daughters to present for such an exchange, resorted to the ruse with their wives. The threat was not therefore originally from the kings themselves, but from outside forces that the patriarchs sought protection from. This historical context effectively addresses critical objections, as many arguments regarding these narratives assume that the ruler was the main source of threat.

Other than that, one author can be as easily responsible for a progression of messages (transmitted through subtle variations in the successive stories) as two or more. One might observe a similar dynamic in discussions of the Q/Markan priority hypothesis: a literary hypothesis can sometimes serve as a flexible framework used to support predetermined conclusions.

Some scholars have specific reasons for supposing multiple authors; for instance, Speiser suggested that Abraham would certainly have learned from his first mistake with Pharaoh and not repeated it with Abimelech. However, assuming that a person never makes the same mistake twice contradicts common human experience. Furthermore, under the "diplomatic marriage" paradigm, we aren't really dealing with a "mistake" in the first place but a stratagem.

There is also the question of the appearance of Abimelech in both Gen. 20 and 26, which is taken to prove two different authors; but the explanation that this either involves a dynastic name, or else that this is the same Abimelech much older (Is there a clue of progress in his title changes from "king of Gerar" to "king of the Philistines"? Is there some sign of Abimelech as an old man in Gen. 26 in his habit of being a peeping tom?), are more than sufficient.

A minor objection asks where Jacob and Esau were in Gen. 26, as they would be at least 16 at the time and a dead giveaway to Isaac's status as a married man; this is easily resolved, for in Isaac's large party of relatives and servants there would be more than enough options for passing the twins off as someone else's (or as from another marriage).

Another objection, usually unrelated to JEDP issues, asks how a woman of 90 could be so beautiful as to be desired by the kings. Jewish tradition responded, quite sensibly, that the promise to Abraham and Sarah was fulfilled in process by reversing the aging process and making them young again -- which is indicated in the writer's hints that Sarah was beautiful at age 90, a puzzle they expect us to figure out.

Furthermore, from a historical perspective: The Nuzi tablets, contemporary with Abraham, show that among the Hurrians marriage bonds were most solemn, and the wife had legally, although not necessarily through ties of blood, the simultaneous status of sister, so that the term "sister" and "wife" could be interchangeable in an official use under certain circumstances. Thus in resorting to the wife-sister relationship, both Abraham and Isaac were availing themselves of the strongest safeguards the law, as it existed then, could afford them.