How did Descartes affect 18th and 19th century philosophy?

Answer by  Plato (26)

Since Descartes is most famous for his "Cogito ergo sum", I'd say he most affected philosophy's direction within epistemology. The fundamental "radical skeptical hypothesis" question within epistemology started with Descartes.

Answer by  Mable (3008)

Descartes is famous for his key phrase, "I think therefore I am. " This is his turning point in Skepticism, a methodology springing from questions of whether it is possible to confirm any truths at all. Hence 18th and 19th century philosophy was dogged by epistemology -- the real possibilities of knowledge.