"Even on the issues of multiple authorship [of the Torah] there are Orthodox voices which accept it in one form or another."
The term "multiple authorship" needs clarification. If we exclude the final verses narrating Moshe's death, the view that isolated verses are post-Mosaic (itself a minority view) does not necessarily justify a belief that whole sections are post-Mosaic. I am unaware of any traditional source that espouses this belief, including the sources mentioned in Marc Shapiro's book. The compatibility assumed by some between Orthodox Jewish faith and Biblical Criticism is probably exaggerated or just plain wrong. This is true even if we assume these minority views of post-Mosaic verses are up for grabs, itself a debatable assumption.
