@shay_lsat Words like "corroborate" and "support" do a lot of heavy lifting. If I say that certain evidence supports a certain conclusion that implies that I believe that there is reason to accept that conclusion. A statement of facts is a statement of what I believe the facts to be.

If an argument is ever presented in a passage it pretty much always means that somebody believes that argument and if no other party is attached to an argument then it is probably the author who believes it.

This does not mean, however, that the author will not consider or agree with other perspectives or contradictory evidence.