The Cartesian coordinate plane was invented by French philosopher Rene Descartes in the 17th century. It was a revolutionary development in math because it allowed algebraic equations to be used to describe geometric shapes, providing the first systematic link between these two fields.
Descartes was one of the key figures in the scientific revolution and is sometimes referred to as the father of modern philosophy. He is probably best known for coining the phrase "cogito ergo sum," which means "I think, therefore I am."
His other contributions to mathematics include laying the groundwork for the calculus developed by Newton and Leibniz, discovering an early form of the law of conservation of mechanical momentum and making advances in the field of optics.