Many things prevent knowledge, including the obscurity of the subject and the brevity of human life
ProtagorasNo intelligent man believes that anybody ever willingly errs or willingly does base and evil deeds; they are well aware that all who do base and evil things do them unwillingly.
ProtagorasMan is the measure of all things, of things that are that they are, and of things that are not that they are not.
Protagoras