Rene Descartes is known for the Cartesian coordinate system and the belief that mathematics can explain all of nature. He is the father of analytical geometry (by using algebra to describe geometry). We often relate to his Cartesian coordinate system in maps or graphs to know how far along and how far up it is. He was also the one who invented the representation of unknowns in mathematical equations by using x, y, and z, and then the knowns by using a, b, and c.