During his lifetime, Rene Descartes was known throughout Europe as a leading contemporary scientist. He developed one of the most plausible versions of the new mechanistic, mathematical accounts of the world and used it to provide thorough explanations in the fields of optics, cosmology, physics, physiology, and biology. Within only a few decades of his death, Descartes' scientific system was all but forgotten, eclipsed by the far superior mechanistic, mathematical science proposed by Sir Isaac Newton. Yet, despite the quick downfall of his scientific system, Descartes remains one of the most widely read thinkers of any age. It is not his science that makes up his legacy, but rather the philosophy that he developed to serve as its foundation.