cogito ergo sum

I think therefore I am (famous saying by the philosopher Rene Descartes)

"Cogito, ergo sum" (Latin: "I think, therefore I am") or Dubito, ergo cogito, ergo sum (Latin: "I doubt, therefore I think, therefore I am") is a philosophical statement used by René Descartes, which became a foundational element of Western philosophy. "Cogito ergo sum" is a translation of Descartes' original French statement: "Je pense, donc je suis", which occurs in his Discourse on Method (1637). (See Principles of Philosophy, Part 1, article 7: "Ac proinde hæc cognitio, ego cogito, ergo sum, est omnium prima & certissima, quæ cuilibet ordine philosophanti occurrat.")
See more at Wikipedia.org...

cogito ergo sum, I think therefore I am

I think, therefore I am. (René Descartes)