René Descartes was a French mathematician and philosopher in the 17^{th} century. His writings such as “Discourse on the Method” (1637) and “Meditations on First Philosophy” (1641) are today widely taught and discussed at most of the universities’ philosophy department. Descartes is also renowned for his works in mathematics. He developed incredibly important concepts that are used as references in today’s mathematics such as the Cartesian coordinate system. He is recognized as the father of analytical geometry, which constitutes of the use of algebra in geometry to demonstrate geometric principles. In physics, he worked on the properties of the optical lens and the principle of the rainbows, and he formulates the refraction law. Descartes’ work on mathematics inspired Newton and Leibniz in their effort to develop the branch of modern mathematics through calculus. His interests in physics lead him to explain the phenomena of the rainbows and formulate the law of refraction. His work on optics also lead him to the discovery of the law of reflection.

Descartes considered himself as a devout Catholic. He was afraid of the Inquisition who, during his time, tried Galileo for his work on heliocentric model of the world. That explains why he did not published his book "The World" where he supports Copernican theory that results in Galileo's condemnation by the Inquisition. However, he claims that the truth does not imply an external authority, but relies on the judgment of the individual, certainty. Therefore, each individual is autonomous and turned into a reasoning adult. Descartes’s perspective of the truth had a significant impact on the Enlightenment’s emancipation from God and the Church.

Newton's work has been the most influenced by Descartes' work on philosophy and mathematics.

Sources:

https://www.britannica.com/biography/Rene-Descartes

http://www.philosophers.co.uk/rene-descartes.html