These ones are often the forerunners of methodology of modern science. It seems that Descartes' epistemology is one of the most significant systems which made (of course, along with other thinkers) philosophic background for modern science, skeptical and highly rational.
Both the rise of modern science and the rediscovery of skepticism were key influences on Descartes' epistemology (Stroll; Newman). While Descartes believed that humans were capable of knowledge and certainty and that modern science was developing the superstructure of knowledge, he thought that skepticism presented a legitimate challenge that needed an answer. Thus, the rational cognition was Descartes' answer, but with the number of stipulations.
Descartes considered the supposition that all of one's beliefs are false. But Descartes claimed that it is not possible for all of one's beliefs to be false, for anyone who has false beliefs is thinking and knows that he is thinking, and if the person is thinking, then that person exists (Garza). Also, it was obvious that nonexistent things cannot think. So, "Cogito, ergo sum", i.e. "I think; therefore, I am".