Quote: The funny thing is that subsequent historians and biographers continued to refer to these so-called -original- sources and till today no historian, Muslim or non-Muslim, has ever questioned the authenticity of Al-Tabri and Ibn-Ishaq.
With history, it is recorded and reasearched the same way as the hadiths are researched i.e. character of narrator, strength of the report etc.
The works of Ibn Ishaq (the seerah of rasool SAW) you will find that the seerah is not like a normal story book. Rather, each incident and report is reported back to the narrator etc. The narrators had heard of incidents of Rasool from those who were in contact with the Tabi Tabi'een.
There was no reason to write books during the time of the Khulafa Rashida and it was only after a few generations did people start to write works in form of books. In the same way books of hadith were (surely going by this argument then they too need authenticating etc.
So in this way, the authenticity of such works are verified and there are no reasons why they should be checked.