The first assumption that all ancient interpreters seem to share is that the Bible is a fundamentally cryptic document. That is, all interpreters are fond of maintaining that although Scripture may appear to be saying X, what it really means is Y, or that while Y is not openly stated by Scripture, it is somehow implied or hinted at in X....Now it is hardly a natural thing to assume that a particular text is fundamentally cryptic or esoteric. Whether we are reading a history book or a newspaper editorial or a rousing hymn, we generally assume that what the words seem to say is what they mean to say.

The second assumption shared by all ancient interpreters was that Scripture constitutes one great Book of Instruction, and as such is a fundamentally relevant text. To appreciate the significance of this assumption, contrast it to the approach we normally take to the act of reading. If, for example, we were to open up Gilgamesh or the Enuma Elish or some other ancient Near Eastern text, we might find the stories moving, the language stirring, but no one would likely suggest that we ought to behave in keeping with what is written there.

The third basic assumption is that Scripture is perfect and perfectly harmonious. By this I mean, first of all, that there is no mistake in the Bible, and anything that looks like a mistake -- that fact that, for example, Gen. 15:13 asserts that the Israelites "will be oppressed for four hundred years" in Egypt, while Exodus 12:41 speaks of 430 years, whereas a calculation based on biblical genealogies yielded a figure of 210 years -- must therefore be an illusion to be clarified by proper interpretation.

The fourth assumption is that all of Scripture is somehow divinely sanctioned, of divine provenance, or divinely inspired. Needless to say, much of Scripture itself asserts that its words come from God: "Thus says the Lord" is the introductory proclamation of many a prophet, and biblical laws in the Pentateuch are frequently introduced with "And the Lord spoke to Moses, saying..." Yet this very fact might have implied to ancient interpreters that the rest of Scripture was somehow of human fashioning -- that, for example, the history of intrigue in David's court, or the corpus of supplications and praises directed to God in the book of Psalms, or many other texts within the canon could not have come from God in the same manner as divine prophecies or laws.

The divine provenance of Scripture is a notion specifically addressed only rather late in the history of ancient interpreters, and it even seems to be contradicted here or there by some ancient writers, whereas the first three assumptions are attested across the whole spectrum of ancient interpreters, early and often.

 
From Kugel, James L. The Bible As It Was. Cambridge, MA: Belknap, 1997 (pp. 18-23).