René Descartes is known for the famous quote "I think, therefore I am" ("Cogito, ergo sum"). This philosophical statement, arising from his work in the 17th century, forms a fundamental element of Western philosophy. Descartes used it as a foundational element in his argument for existence, asserting that the very act of thinking implies a thinking subject. It highlights the importance of doubt and inquiry and serves as a starting point for discussions about consciousness and existence. Descartes' thoughts laid the groundwork for modern philosophy and influenced various fields, including metaphysics and epistemology.