I never remember reading an utterance by any famous philosopher which seems to me fit to be compared with words my friend John Colet, a man of equal scholarship and integrity, used to repeat: ‘We are, what we are made by our daily conversation: we are shaped by what we hear round us every day.’ And what he said about conversation is also to be understood of what we read. Those who spend their whole lives on gentile literature end up as pagans; those who read nothing but filthy books must needs develop in their own characters a streak of filth. For reading surely is a kind of conversation.
(Erasmus of Rotterdam, Adages. Toronto: University of Toronto Press, 1989, p. 268).