On Truth by Parmenides b 519 BC
Channel: Age of Enlightenment
Date: 2016-08-06

Come now, I will tell thee—and do thou hearken to my saying and carry it away—the only two ways of search that can be thought of. The first, namely, that It is, and that it is impossible for it not to be, is the way of belief, for truth is its companion. The other, namely, that It is not, and that it must needs not be,—that, I tell thee, is a path that none can learn of at all. For thou canst not know what is not—that is impossible—nor utter it; for it is the same thing that can be thought and that can be.

https://archive.org/stream/journalofspecula04harruoft#page/4/mode/1up