What did Descartes mean by i think therefore i am?

Answer 1

"I think; therefore I am" was the end of the search Descartes conducted for a statement that could not be doubted. He found that he could not doubt that he himself existed, as he was the one doing the doubting in the first place. In Latin (the language in which Descartes wrote), the phrase is "Cogito, ergo sum."

Answer 2

Descartes meant that the act of doubting one's existence proves that one must exist to do the doubting. "I think, therefore I am" (Cogito, ergo sum) is a foundational element of his philosophy, serving as a starting point for establishing certainty in knowledge.