The other major philosophical group during the seventeenth and eighteenth century was the classical British empiricists. The empiricists believed that all knowledge is derived from observation. Hume and other British empiricists rejected the intuition/deduction thesis and the idea of innate knowledge proposed by Descartes. Hume believed that true knowledge came from a posteriori, sense experience, rather than from a priori. A major difference between Hume and Descartes is their take on the issue of God’s existence. When the two applied their very different theories to the topic of Gods existence, they arrived at different conclusions. In Descartes efforts to doubt everything, he realized that only one thing was certain, “I think, therefore I exist”. Descartes concluded that God exists when he realized that if he himself is subject to doubt, he is imperfect, and cannot be the cause of his existence. Because he had an idea of perfectness, this idea must come from a perfect being, or God. However, Hume was not able to prove God’s existence. Hume built upon Leibniz’s analytic synthetic distinction in creating his “Humean Method”. He separated ideas into three categories: analytic propositions, synthetic propositions, and nonsense. He created a set of questions that one could ask to come to the conclusion as to what category an idea fell under. In contrast to Descartes conclusions about God’s existence, the Humean method suggests that God should be placed under the “nonsense” category because it is not possible to trace God back to sense data. Descartes, the rationalist and Hume, the empiricist had differing opinions. However, the two philosophers are similar because they both raise very skeptical issues. Descartes idea of the possibility of an evil demon putting thoughts in our heads and Hume’s conclusion that the idea of God is “nonsense” caused people to begin questioning traditional teachings and what they had always thought to be true. New ideas like the ones presented by Descartes and Hume later caused problems because as people became more aware of these ideas, more rebellion from authority and religion began to occur.