Art has posted some thoughts on how authorship was understood in the ancient world (reflecting on Karel van der Toorn's Scribal Culture and the Making of the Hebrew Bible). Here's his final thought.
The point of writing this is to ask a question: if our understanding of authorship and our concept of author is a modern understanding that is pushed back onto the Hebrew Bible, then why do people make such a fuss about the Mosaic authorship of Torah or of Isaianic authorship of Isaiah or of Solomonic authorship of Proverbs, etc.? After looking at the data within the Hebrew Bible itself as well as the data within the historical milieu of the Hebrew Bible, to continue arguing issues of authorship seems to be not so much arguing for a “high view of Scripture” as much as it is arguing for a “high view of modern categories.” [emphasis added]I've been wondering the same thing for a long time, Art. For some reason, their very ability to believe Scripture is divine seems to hang on it. I wrestled with the issue a while back in my posts on apologetics and Bible scholarship because those are the very issues that come up for debate. Somehow it's essential for inerrancy and inspiration. But I agree with Art's assessment that it's an argument from modern categories more than anything else. (See McGrath's review of Beale's book on the inerrancy debate for much the same assessment of his argument.)