Xenophanes, DK Fragment B 34 (Sextus Empiricus, Against the Mathematicians VII 49)
And the clear truth no man has seen nor will anyone know concerning the gods and about all the things of which I speak; for even if he should actually manage to say what is the case, nevertheless he himself does not know it; but belief is found over all.
Plato, Timaeus, page 48
For the present, however, let our procedure be as follows. We shall not now expound the principle of all things—or their principles, or whatever term we use concerning them; and that solely for this reason, that it is difficult for us to explain our views while keeping to our present method of exposition. You, therefore, ought not to suppose that I should expound them, while as for me—I should never be able to convince myself that I should be right in attempting to undertake so great a task. Strictly adhering, then, [48d] to what we previously affirmed, the import of the “likely” account, I will essay (as I did before) to give as “likely” an exposition as any other (nay, more so), regarding both particular things and the totality of things from the very beginning. And as before, so now, at the commencement of our account, we must call upon God the Saviour to bring us safe through a novel and unwonted exposition [48e] to a conclusion based on likelihood, and thus begin our account once more.