Is it possible to be certain of anything? If so, how? René Descartes (1596-1650), the father of modern philosophy and founder of rational method in philosophical thought, sought the answers to these questions. In Discourse on Method, he formulated a scientific approach comprising four principles: to accept only what reason recognizes as "clear and distinct"; to analyze complex ideas by dividing them into smaller elements; to reconstruct the ideas; and to make accurate, complete enumerations of the data. In Meditations, he proceeds according to this method, exploring the mind/body distinction, the nature of truth and error, the existence of God, and the essence of material things.