"Eeegaads!"

D. Graham Burnett interviews Anthony Grafton for Cabinet on deception, forgery and the early modern historical sense (via Bookforum):

In the early fifteenth century, an exceedingly learned Latinist, Lorenzo Valla, rolled up his philological sleeves and red-penciled a copy of the Donation. “Wait a second,” he says, “this doesn’t look to me like the kind of Latin they were writing in the fourth century!” And he amasses this magnificent demonstration that the Donation could not have been written when its author claimed. They just didn’t use the language of the document in those days. Now, people had argued about this text since forever, but everyone before Valla had basically been preoccupied by its juridical elements (as in, exactly what implications did it have for the proper relationship between emperors and popes, etc., etc.). Valla bracketed those thorny legal questions and went after the document in a different way.

­He went after it historically.

Yes, philologically. And to do that, you really have to have a very deep sense of how language works, to be sure, but you also need to have an equally deep sense of how time works; you need to understand that a given period has a style in everything that it does, from plumbing to personal relations, and that any product of the period has to show the traits of that period and style.