3. He might have found them in written documents existing at
the time of his writing.

As many of the laws and incidents in the books of Moses were known
to the Chaldeans, the "direct revelation of God" theory is not
plausible. On this point Dr. Gladden's opinion supports mine. He
says, on page 61:

That such is the fact with respect to the structure of these
ancient writings is now beyond question. And our theory of
inspiration must be adjusted to this fact. Evidently neither
the theory of verbal inspiration, nor the theory of plenary
inspiration, can be made to fit the facts, which a careful study
of the writings themselves brings before us. These writings are
not inspired in the sense which we have commonly given that word.
The verbal theory of inspiration was only tenable while they
were supposed to be the work of a single author. To such a
composite literature no such theory will apply. "To make this
claim," says Professor Ladd, "and yet accept the best ascertained
results of criticism, would compel us to take such positions
as the following: the original authors of each one of the
writings which enter into the composite structure were infallibly
inspired; every one who made any changes in any one of these
fundamental writings was infallibly inspired; every compiler
who put together two or more of these writings was infallibly
inspired, both as to his selections and omissions, and as to any
connecting or explanatory words which he might himself write;
every redactor was infallibly inspired to correct and supplement,
and omit that which was the product of previous infallible