Cartesian doubt

Cartesian doubt is a form of methodological skepticism or scepticism associated with the writings and methodology of René Descartes (1596-1650). Cartesian doubt is also known as Cartesian skepticism, methodic doubt, methodological skepticism, Universal 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. This method of doubt was largely popularized in Western philosophy by René Descartes, who sought to doubt the truth of all his beliefs in order to determine which beliefs he could be certain were true.

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 pure knowledge.

Cartesian doubt is methodological. Its purpose is to use doubt as a route to certain knowledge by finding those things which could not be doubted. The fallibility of sense data in particular is a subject of Cartesian doubt.

There are several interpretations as to the objective of Descartes' skepticism. Prominent among these is a foundationalist account which claims that Descartes' skepticism is aimed at eliminating all belief which it is possible to doubt, thus leaving Descartes with only basic beliefs (also known as foundational beliefs). From these indubitable basic beliefs, Descartes then attempts to derive further knowledge. It's an archetypal and significant example that epitomizes the Continental Rational schools of philosophy.

Descartes' method of hyperbolic doubt included:

Hyperbolic doubt means having the tendency to doubt, since it is an extreme or exaggerated form of doubt. (Knowledge in the Cartesian sense means to know something beyond not merely all reasonable, but all possible, doubt.) In his Meditations on First Philosophy (1641), Descartes resolved to systematically doubt that any of his beliefs were true, in order to build, from the ground up, a belief system consisting of only certainly true beliefs. Consider Descartes' opening lines of the Meditations:

Several years have now elapsed since I first became aware that I had accepted, even from my youth, many false opinions for true, and that consequently what I afterward based on such principles was highly doubtful; and from that time I was convinced of the necessity of undertaking once in my life to rid myself of all the opinions I had adopted, and of commencing anew the work of building from the foundation...

...
Wikipedia