The famous philosopher associated with the quote "I think, therefore I am" is René Descartes. This phrase, originally in Latin as "Cogito, ergo sum," is foundational to his philosophy and epistemology, expressing the idea that the very act of doubt or thinking is proof of one's existence. Descartes' work in the 17th century laid the groundwork for modern philosophy, particularly in the fields of metaphysics and epistemology. His emphasis on rational thought and skepticism helped shape the direction of philosophical inquiry, asserting the importance of reason as a tool for understanding the world and one's place within it.