France: Day 1 - Descartes

Today is the birthday of Charles Reyneau born 16546 in Brissac, Maine-et-Loire, France. Reyneau published one of the first influential textbooks on the newly invented calculus.

Today's quote is by Rene Descartes entitled, Cogito ergo sum. "... Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us; and because some men err in reasoning, and fall into paralogisms, even on the simplest matters of geometry, I, convinced that I was as open to error as any other, rejected as false all the reasonings I had hitherto taken for demonstrations; and finally, when I considered that the very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep, while there is at that time not one of them true, I supposed that all objects (presentations) that had ever entered into my mind when awake, had in them no more truth than illusions of my dreams. But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth; I think, therefore I am, was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the skeptics capable of shaking it, I counted that I might, without scruple, accept it as the first principle of the philosophy of which I was in search."

As witnessed when I watch a recent news segment, I am on "assignment" which means I am on vacation, and will be writing about my five favorite French mathematicians; Rene Descartes, Sophie Germain,  Pierre de Fermat, Emilie du Chatelet, and Cedric Villani.

Rene Descartes

Descartes was born on March 31, 1596 in La Haye, France. As a student, he studied rhetoric, logic, and the "mathematical arts". "Mathematical arts" included mathematics, music, astronomy, metaphysics, natural philosophy, and ethics. He attended the University of Poitiers and obtained a law degree.

After graduation, he studied medicine and theology. He traveled and joined the army. During his stint in the army, he met scientist and philosopher, Isaac Beeckman. Beeckman convinced Descartes that he should apply mathematics and logic to understand the natural world.

Descartes is considered the father of modern philosophy. He believed that all truths are ultimately linked and that the rational structure of mathematics and science could be used to uncover the meaning of the natural world.

Descartes introduced Cartesian geometry which is a fusion of geometry and algebra. I call Cartesian geometry, coordinate geometry. I love coordinate geometry and I believe its application allowed me to have an easy transition in to trigonometry and polar coordinates. Descartes also developed laws of refraction and formed a practical understanding of rainbows. Pope Alexander VII placed Descartes' writings on the Index of Prohibited Works.