When you encounter a book of the Bible, what you have in front of you is a text — a long string of words, probably with punctuation of some sort, and numbers interspersed here and there. You, the reader, are there. The text is there.
What’s missing is the author. The author has to be inferred. This is true even when reading a modern book, like, say, the autobiography of Colin Powell. You can’t actually see what’s going on from inside Mr. Powell’s head. You read along, and between what you know from your own experience, and the information coming in from the text, you make inferences. If this process goes well, you’ll wind up with a pretty accurate idea of what kind of person Colin Powell is. Or maybe, depending on who’s yardstick of success we are using to measure the process, you will wind up with an idea of what kind of person Colin Powell wants to portray himself as.
Now, in the case of a modern book, we expect there to be an identifiable author, who is responsible for the contents, which all reflect that authors view of things. The author is always credited. In the case of Powell’s book, he wrote with the assistance of a man named Joseph Persico, and, as our culture’s norms require, Persico was duly credited in the front matter of the book.
This is where a modern reader might import modern assumptions and misunderstand. It is not necessarily the case that a text in the ancient world had a credited author. Indeed, the books of the Hebrew Bible are mostly anonymous. And it is also not necessarily the case that a text in the ancient world had a single author who produced it all at once.
One thing that stands out right away in reading the Hebrew Bible is that many of the books do not name an author. So when you read a book like, for example, Esther, it is not immediately obvious who produced the text. Perhaps Esther is a story written by one author. Perhaps a rough draft was written by one author, which was then polished and expanded upon by a second author. Perhaps Esther began as two different stories, by two different authors, which were then skillfully woven together into a single tale. Or perhaps it was composed by 4,932 different authors, each of whom contributed a single word, mad-libs style.
The best we can do is carefully weigh whatever evidence is available to get a picture of how the book was written.
And so I apologize in advance for talking about “the author” without further elaboration when commenting on some biblical text.
When I speak of “the author” of something, feel free to substitute mentally, “whoever, singular or plural, acted as an author, authors, or redactor in shaping the text we have today”.