René Descartes

René Descartes is often called the father of modern philosophy. His method of radical doubt led to the famous conclusion "Cogito, ergo sum" (I think, therefore I am) — the one truth he found impossible to doubt.

Descartes developed a dualist philosophy that separates mind from body, and he championed rationalism — the idea that knowledge comes primarily from reason rather than sensory experience. His Meditations on First Philosophy remains essential reading in epistemology.