1) Even within the narrative, Socrates isn't "speaking". He is creating a fictional narrative set in Ancient Egypt where he believed writing originated (wrongly, but that isn't the point). 2) On a second level, Socrates didn't even write this. This is part of Plato's work. Plato was a student of Socrates, and maybe is describing something Socrates really said. Or maybe not. He may be simply giving his own opinion and attributing it to Socrates, who had a higher reputation.