This upper limit, of earth at our feet is visible and touches the air, but below it reaches to infinity
XenophanesEven if a man should chance to speak the most complete truth, yet he himself does not know it; all things are wrapped in appearances
XenophanesThe clear and perfect truth no man has seen, nor will there be anyone who knows about the gods and what I say about all things...; for, however perfect what he says may be, yet he does not know it; all things are matters of opinion.
Xenophanes