So all historians are able to basically bear witness to every single moment of say a given time period or individual they are studying? or all artefacts and all materials written on that subject? Yes they will apply great rigour to their subject, but quite a few of us on the Caf have actually spent time looking through most if not all the historic games that the old great players played in. Exactly if you haven't watched it or listened to it, don't offer an opinion. I have watched Pele play and watched substantial amounts of footage on him, therefore I can offer an opinion. Do you see where I am going with that?
It would be different if I was comparing him to say Leonidas of Brazil of the 1930's but Pele played in the television era, thanks to the internet - there is vast swathes of footage on him playing.
http://footballia.net/
Great website above, which has links to all sorts of games for historic matches.
As for Pele, here is a recent post on him:
Auction-Trade Madness Draft - QF: Raees/Invictus vs Skizzo
A truly complete player beyond compare IMO.