The Bible as a whole makes no claim for divine authorship. Although many passages are quoted in God's name, the five books of Moses (Genesis through Deuteronomy) never assert that their entire content is divine. Nonetheless, due to various interpretations and doctrines, the belief has grown up in Judaism that the whole Torah (and to a certain extent, the subsequent biblical books and even the rabbinic tradition) is divine.
One engine of this belief is the existence of a fascinating intellectual problem. In modern times, the problem is called "the slippery slope." Essentially, it points up the difficulty with drawing lines. Opponents of abortion use the slippery-slope argument very effectively: If a fetus is considered a human being at, say, eight months, what about eight months minus 30 seconds? Minus one minute? Five minutes? One day? At each step, it is hard to defend the absolute distinction between the point one defends and a point just marginally prior to it.
Similarly, the slippery slope wreaks havoc with arguments about biblical authorship. If one word, just one word, of the Bible is in fact of human origin, then how can one defend the divinity of any of it? If one word, why not two, or 10, or the whole book?
So it is intellectually neater to hew to a hard line. If it is all from God, then that's the end of it. For centuries, Jewish exegetes (those who interpret texts) argued that this was the simple truth.
Unfortunately, the evidence does not always cooperate with our intellectual convenience. Once various other academic disciplines began to be developed--literary criticism, comparative religion, archaeology, and so forth--the divinity of the Bible seemed less secure.
Once all this evidence began to be accumulated, those who read the Bible were left with several choices. One could simply ignore the evidence, refuse to read the studies of biblical critics, and continue to believe that the traditional interpretations survived intact.
Alternatively, one could marshal one's intellectual forces, as many have done, and attack the conclusions of the scholars with counter-arguments by believers. After all, many of the inconsistencies noted by biblical critics were noted and discussed centuries before.
Yet as time has passed, these arguments have seemed increasingly strained, because the accumulation of evidence is by now not merely formidable, but mountainous. Yet there is nothing so flexible and resourceful as human reason deployed in a cause, so many still seek to rebut the conclusions of biblical critics, and some do so with considerable skill and elan.
Finally, one could seek, as many have, to straddle the ideological divide. Perhaps the Bible was written by human beings, wholly or in part. Does this necessarily mean that it has no divinity in it? Must the realization that human hands were involved in the gathering of traditions mean that it is the spiritual equivalent of Shakespeare--remarkably insightful and beautiful, but having no special standing in the cosmos?
Liberal theologians (here meaning those who believe in the human authorship of the Torah) struggle to maintain the Torah's special status without violating what they believe to be the canons of intellectual integrity.
Others have sought to argue that the Bible is a human record of response to God's self-revelation. God somehow--in ways not exactly describable in human language--was made manifest in the Sinai desert, and perhaps at other times, and human beings wrote of their struggle to comprehend that appearance.
This seems close to what the theologian Abraham Joshua Heschel meant when he said that the Bible was a "midrash," that is, an interpretive story. He argued that the Bible was a record of God's search for human beings and the human search for God; the cardinal sin in reading the Bible, said Heschel, was "literal-mindedness."