Both :) In formal/academic writing, you would normally find Present Simple used for factual language. Example: Krashen (1989) tells us that the principles and practices the concern this..... It also depends on the speaker if the person being quoted is still alive or not. Compare: Professor Brian Cox insists on a more 'down to earth' conveyance of information, He says that his style is more.... Plato played to his audience and preyed upon their fears, and told them of the dangers that lay....