Cartesian doubt is a form of methodological skepticism associated with the writings and methodology of René Descartes (March 31, 1596–Feb 11, 1650). Cartesian doubt is also known as Cartesian skepticism, methodic doubt, methodological skepticism, universal doubt, systematic doubt, or hyperbolic doubt.
Cartesian doubt is a systematic process of being skeptical about (or doubting) the truth of one's beliefs, which has become a characteristic method in philosophy. Additionally, Descartes' method has been seen by many as the root of the modern scientific method. This method of doubt was largely popularized in Western philosophy by René Descartes, who sought to doubt the truth of all beliefs in order to determine which he could be certain were true. It is the basis for Descartes' statement, "Cogito ergo sum" (I think, therefore I am). A fuller version of his phrase: "dubito ergo cogito, cogito ergo sum" translates to "I doubt therefore I think, I think therefore I exist." Sum translated as "I exist" (per various Latin to English dictionaries) presents a much larger and clearer meaning to the phrase.
Methodological skepticism is distinguished from philosophical skepticism in that methodological skepticism is an approach that subjects all knowledge claims to scrutiny with the goal of sorting out true from false claims, whereas philosophical skepticism is an approach that questions the possibility of certain knowledge.