Descartes believed in rationalism and the principle of certainty: if he perceives something clearly and distinctly, he must know it with certainty. However, one can easily dismiss this theory. If I perceive a brown dog, but someone else sees it as distinctly black, who is right? This concept leaves room for human error in individual thinking. Rationalists, like Descartes, also see science as proof that humans can acquire certain and true knowledge. However, this ideology does not explain whether we have propositional knowledge and, if we have it, how much of it we have. Taking a more empiricist approach, like Hume, science shows us evidence that human beings can never be absolutely certain of their theories, conceptions and understandings. Science demonstrates how long the unknown exists in the real world and the lack of knowledge we possess. Skepticism should be embraced because we do not have complete knowledge and can never be absolutely certain of theories, conceptions and understandings of the world.