I am not well versed in what to do with Biblic genealogies - for instance, the numerous places in Scripture that place Moses just 2 generations removed from Levi. I would agree with you that it seems reasonable to presume this to be a complete genealogy, and to presume that Abraham fathered children of three women and no more. But I would have little with which to defend that view and little basis for daring to hold the view with reasoned confidence. In general, I am "wired" to adopt plain, less contorted readings, as our discussion of the chronology of 1 Sa. 16-17 revealed sometime back. Being wired a certain way, however, proves nothing other than that I am free to follow my own inclinations.
I was using the term "genealogy" here not in reference to a list of names (parent/child); but to the literary structure of Genesis. There are no "isolated predicates," by which I mean that an interpreter is
literarily (not the word "literally") bound to the context and cohesion of the text presented.
Logically it could be accurate to point out: by a strict law of deduction, the statement about Abraham's concubines and offspring does not
in isolation preclude there being more than two such. However, that conclusion is practically indefensible from a
literary standpoint.
In other words, proper interpretation does not rest on pure logic treating a given indicative sentence as if it was written so as to be a floating premise with positive truth value--combine two such, and out comes a valid conclusion; or parse one, in order to deduce all possible implications, any which must be positively refuted by some other true premise in order to be invalidated. Treating the text of Scripture thusly is irresponsible, because it dethrones context and genre as indispensable literary guardrails. We are not free to follow our own interpretive inclinations, if we desire to cleave to the mind of Moses (and above him the mind of the Spirit) who presents us with data embedded in a narrative, or a sermon, or a poem, etc.; and more broadly in a book or a set of them. Those genres and contexts establish parameters and help us decide what in fact are reasonable investigations and conclusions, or what is likely to be a fruitless speculation.
There is an art as well as a science of the interpretive craft. I wish you many happy explorations using the best tools and rules for biblical interpretation, and pray you might be free from unprofitable sidetracks resulting from either no discipline, or an excessive dedication to a single (mythical) "golden key" for unlocking the mysteries and accompanying deprecation of the tool kit (monomania is also lack of discipline).
