Omar Khayyam (translated) in The Rubaiyat

Myself when young did eagerly frequent
Doctor and saint, and heard great argument
About it and about, but evermore
Came out by the same door as in I went

Cicero

No well-informed person ever imputed inconsistency to another for changing his mind.

Descartes

“Cogito, ergo sum”: I think, therefore I am.