“Cogito Ergo Sum.

I Think, Therefore I Am…”

—René Descartes

Descartes' Discourse marks a breakpoint in European thought: in it, he sets out a radical new philosophy, which begins with a proof of the existence of the self (the famous "cogito ergo sum").

Next he deduces from it the existence and nature of God, and ends by offering a radical new account of the physical world and of human and animal nature.

Written in language accessible to all, it swept away all previous philosophical traditions.

René Descartes (1596–1650) was a French philosopher, mathematician and writer. Called the father of modern philosophy, much subsequent Western philosophy is a response to his writings, which are studied closely to this day.

Descartes' influence in mathematics is equally apparent: the Cartesian coordinate system, allowing reference to a point in space as a set of numbers, and allowing algebraic equations to be expressed as geometric shapes in a two-dimensional coordinate system (and conversely, shapes to be described as equations), was named after him.

He is likewise credited as the father of analytical geometry: the bridge between algebra and geometry, crucial to the discovery of infinitesimal calculus and analysis.