Descartes vs. Pascal For centuries, human beings have been debating over the validity of the use of reason. This is a very, very difficult subject to discuss, as one is forced to study something which is at that moment being used in their study. Two classic thinkers who contrasted on their view of reason were Descartes and Pascal. Though both saw reason as the primary source of knowledge, they disagreed over the competence of human reason. Descartes, the skeptic, said that we could use reason to find certain truth if we used it correctly, while Pascal said that we can't know certain truth, but reason is the best source of knowledge that we have. Descartes: Reason is the tool