René Descartes was famous for being a natural scientist in addition to a philosopher. He underlined how the natural world could be understood by intellect and observation. His argument was that philosophical reason was required to understand the natural sciences and that studying the natural sciences was crucial to expand human knowledge. He employed what is called a mechanistic approach to his study of science, meaning that he assumed all natural phenomena have rational, scientific explanations.
Descartes also connected his spiritual beliefs with his study of the natural sciences. For example, he believed that the distinction between humans and non-human animals was that the latter lacked consciousness and a soul. However, he did recognize anatomical similarities between humans and non-human animals.
Ultimately Descartes’s beliefs show how philosophy attempts to explain what is at the root of nature. The field of philosophy questions the reasoning for things like human existence, non-human existence, and even reason itself. Descartes’s mechanistic approach helps show why philosophy would also question the way science works. For example, a philosopher might look at Descartes’s approach and question why all natural phenomena have a scientific explanation. Why does life on Earth work that way, or is there no reason for it at all?