René Descartes, a French philosopher, mathematician, and scientist, famously said "Cogito, ergo sum," which translates to "I think, therefore I am." This philosophical statement emphasizes the act of thinking as proof of one's existence. Written in "Meditations on First Philosophy" in the 17th century, Descartes sought to establish a foundation for scientific knowledge and argue against skepticism. His work laid the groundwork for modern philosophy, touching on metaphysics and epistemology. Descartes' assertion has become a fundamental element in discussions about consciousness, existence, and the nature of reality, influencing many subsequent philosophers and cognitive scientists.