No, it isn't because you could come up with one tomorrow sane. It seems they are above argument from modernity or antiquity.
There is material of interest to historians and there is material of interest to philosophers. Each type of material has it's own support. Different rules on validity are used in analysis.
Could I? How could you tell?
As to your seond sentence, you are correct. But that just backs up Dicky's post, and my elaboration of the issue of meaning. Changes in meaning, lack of clarity, lack of discussion all effect how you approach both philosophical documents and historical documents though and you don't appear to understand that