René Descartes (1596–1650) was a French scientist, philosopher and Roman Catholic of the Enlightenment period who is often considered to be the founder of modern philosophy, breaking away from the ways of the middle ages.

Descartes departs from the philosophy of scholasticism with a concept of universal doubt. He put much faith in the scientific method as a source of knowledge.

Descartes was famous for the idea of "Cogito, ergo sum" (Originally written as "Je pense, donc je suis", both meaning "I think, therefore I am")—meaning that any thinking being rather promptly asserts and proves its own existence, if only to itself. Descartes wanted to reconstruct his own beliefs on a purely rational basis, and began by doubting everything he believed. He arrived at a single piece of knowledge that he could not reasonably doubt, which is "I think, therefore I am", an argument often referred to as "the Cogito".

In his attempt to rebuild his beliefs, Descartes also sought to prove the existence of God through the idea of God in the mind of a thinking being. He also accepted the ontological proof of God that had been previously described by St. Anselm. Following this assertion, he believes the reality of the physical world as we know it through the conclusion that God would not try to fool the thinkers with illusions.

For Descartes, the physical world and the human mind are completely distinct entities, connected only through God.

Philosophers generally agree that Descartes was fundamentally unable to reconstruct his beliefs in a purely rational manner, and still hold that the Cogito may be the only knowledge that we can hold from reason alone. The response to the perceived failure of Descartes' work has been mixed. Later Enlightenment philosophers, such as Kant sought to hold onto the values of the Enlightenment thinking, chiefly that human beings know things primarily through reason. Other philosophers, particularly David Hume and Thomas Reid, rejected the foundation of Descartes' argument, in favour of the view that certain empirical assumptions are neccessary for knowledge.

Despite the general failure of Descartes' overall goal, his work sparked a great transition in the direction of philosophy and has great influence on philosophical work today. Additionally, René Descartes made several advances in science and mathematics, particularly in geometry and algebra.

Descartes' Works

• Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences (1637)
  
• Meditations On First Philosophy (1641)