What concept did René Descartes famously coin?

René Descartes coined the phrase "I think therefore I am" (in Latin, "Cogito, ergo sum") as a fundamental element of his philosophy. This statement encapsulates Descartes' exploration of existence, consciousness, and self-awareness. Its significance lies in the assertion that the very act of thinking is proof of one's own existence. In the context of Descartes' method of radical doubt, he sought to find an indubitable foundation for knowledge. By doubting everything that could be doubted, he found one certainty: the existence of his own consciousness as a thinking being. This idea was pivotal in laying the groundwork for modern philosophy, especially concerning subjects of knowledge, identity, and existence.

The other concepts, while significant in philosophical discourse, do not originate from Descartes. "Existence precedes essence" is associated with existentialist philosophers like Jean-Paul Sartre, "Knowledge is power" is attributed to Francis Bacon, and "The unexamined life is not worth living" comes from Socrates as recorded by Plato.