Cartesian doubt

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Cartesian doubt is a form of methodological skepticism associated with the writings and methodology of René Descartes (15961650). [1] [2] Cartesian doubt is also known as Cartesian skepticism, methodic doubt, methodological skepticism, universal doubt, systematic doubt or hyperbolic doubt.

René Descartes 17th-century French philosopher, mathematician, and scientist

René Descartes was a French philosopher, mathematician, and scientist. A native of the Kingdom of France, he spent about 20 years (1629–49) of his life in the Dutch Republic after serving for a while in the Dutch States Army of Maurice of Nassau, Prince of Orange and the Stadtholder of the United Provinces. He is generally considered one of the most notable intellectual figures of the Dutch Golden Age.


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. It is the basis for Descartes' statement, " Cogito ergo sum " ("I think, therefore I am").

Philosophy intellectual and/or logical study of general and fundamental problems

Philosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, reason, mind, and language. The term was probably coined by Pythagoras. Philosophical methods include questioning, critical discussion, rational argument, and systematic presentation. Classic philosophical questions include: Is it possible to know anything and to prove it? What is most real? Philosophers also pose more practical and concrete questions such as: Is there a best way to live? Is it better to be just or unjust? Do humans have free will?

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.

Philosophical skepticism is a philosophical school of thought that questions the possibility of certainty in knowledge. Skeptic philosophers from different historical periods adopted different principles and arguments, but their ideology can be generalized as either (1) the denial of possibility of all knowledge or (2) the suspension of judgement due to the inadequacy of evidence.


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.[ citation needed ]

Foundationalism concerns philosophical theories of knowledge resting upon justified belief, or some secure foundation of certainty such as a conclusion inferred from a basis of sound premises. The main rival of the foundationalist theory of justification is the coherence theory of justification, whereby a body of knowledge, not requiring a secure foundation, can be established by the interlocking strength of its components, like a puzzle solved without prior certainty that each small region was solved correctly.

Basic beliefs are, under the epistemological view called foundationalism, the axioms of a belief system.

In philosophy, rationalism is the epistemological view that "regards reason as the chief source and test of knowledge" or "any view appealing to reason as a source of knowledge or justification". More formally, rationalism is defined as a methodology or a theory "in which the criterion of the truth is not sensory but intellectual and deductive".


Descartes' method of hyperbolic doubt included:

  1. accepting only information you know to be true
  2. breaking down these truths into smaller units
  3. solving the simple problems first
  4. making complete lists of further problems

Hyperbolic doubt means having the tendency to doubt, since it is an extreme or exaggerated form of doubt. [3] (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; his end goal—or a major one, at the least—was to find an undoubtable basis for the sciences. Consider Descartes' opening lines of the Meditations:

<i>Meditations on First Philosophy</i> philosophy book by Descartes

Meditations on First Philosophy in which the existence of God and the immortality of the soul are demonstrated is a philosophical treatise by René Descartes first published in Latin in 1641. The French translation was published in 1647 as Méditations Métaphysiques. The title may contain a misreading by the printer, mistaking animae immortalitas for animae immaterialitas, as suspected by A. Baillet.

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...

René Descartes, Meditation I, 1641

Descartes's method

René Descartes, the originator of Cartesian doubt, put all beliefs, ideas, thoughts, and matter in doubt. He showed that his grounds, or reasoning, for any knowledge could just as well be false. Sensory experience, the primary mode of knowledge, is often erroneous and therefore must be doubted. For instance, what one is seeing may very well be a hallucination. There is nothing that proves it cannot be. In short, if there is any way a belief can be disproved, then its grounds are insufficient. From this, Descartes proposed two arguments, the dream and the demon. [2]

Hallucination perception in the absence of external stimulation that has the qualities of real perception

A hallucination is a perception in the absence of external stimulus that has qualities of real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. They are distinguishable from several related phenomena, such as dreaming, which does not involve wakefulness; pseudohallucination, which does not mimic real perception, and is accurately perceived as unreal; illusion, which involves distorted or misinterpreted real perception; and imagery, which does not mimic real perception and is under voluntary control. Hallucinations also differ from "delusional perceptions", in which a correctly sensed and interpreted stimulus is given some additional significance.

The dream argument

Descartes, knowing that the context of our dreams, while possibly unbelievable, are often lifelike, hypothesized that humans can only believe that they are awake. There are no sufficient grounds by which to distinguish a dream experience from a waking experience. For instance, Subject A sits at the computer, typing this article. Just as much evidence exists to indicate that the act of composing this article is reality as there is evidence to demonstrate the opposite. Descartes conceded that we live in a world that can create such ideas as dreams. However, by the end of The Meditations, he concludes that we can distinguish dream from reality at least in retrospect: [2]

"But when I distinctly see where things come from and where and when they come to me, and when I can connect my perceptions of them with my whole life without a break then I can be certain that when I encounter these things I am not asleep but awake."

— Descartes: Selected Philosophical Writings [4]

The Evil Demon

Descartes reasoned that our very own experience may very well be controlled by an evil demon of sorts. [5] This demon is as clever and deceitful as he is powerful. He could have created a superficial world that we may think we live in. [2] As a result of this doubt, sometimes termed the Malicious Demon Hypothesis, Descartes found that he was unable to trust even the simplest of his perceptions.

In Meditation I , Descartes stated that if one were mad, even briefly, the insanity might have driven man into believing that what we thought was true could be merely our minds deceiving us. He also stated that there could be 'some malicious, powerful, cunning demon' that had deceived us, preventing us from judging correctly.

Descartes argued that all his senses were lying and since your senses can easily fool you, his idea of an infinitely powerful being must be true as that idea could have only been put there by an infinitely powerful being which would have no reason to be deceitful to him.

I think, therefore I am

While methodic doubt has a nature, one need not hold that knowledge is impossible in order to apply the method of doubt. Indeed, Descartes' attempt to apply the method of doubt to the existence of himself spawned the proof of his famous saying, " Cogito, ergo sum " (I think, therefore I am). That is, Descartes tried to doubt his own existence, but found that even his doubting showed that he existed, since he could not doubt if he did not exist. [2]

See also

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<i>Discourse on the Method</i> book by Descartes

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Simulated reality is the hypothesis that reality could be simulated—for example by quantum computer simulation—to a degree indistinguishable from "true" reality. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation. This is quite different from the current, technologically achievable concept of virtual reality. Virtual reality is easily distinguished from the experience of actuality; participants are never in doubt about the nature of what they experience. Simulated reality, by contrast, would be hard or impossible to separate from "true" reality. There has been much debate over this topic, ranging from philosophical discourse to practical applications in computing.

Evil demon concept in Cartesian philosophy

The evil demon, also known as malicious demon and evil genius, is a concept in Cartesian philosophy. In the first of his 1641 Meditations on First Philosophy, Descartes imagines that an evil demon, of "utmost power and cunning has employed all his energies in order to deceive me." This evil demon is imagined to present a complete illusion of an external world, so that Descartes can say, "I shall think that the sky, the air, the earth, colours, shapes, sounds and all external things are merely the delusions of dreams which he has devised to ensnare my judgement. I shall consider myself as not having hands or eyes, or flesh, or blood or senses, but as falsely believing that I have all these things."

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  1. "A Philosophical Glossary" edited by Justin Leiber, Philosophy Department, University of Houston, USA.
  2. 1 2 3 4 5 Roger Scruton. Modern Philosophy: An Introduction and Survey. London: Penguin Books, 1994.
  3. Skirry (2006).
  4. Descartes, René (1988-02-26). Descartes: Selected Philosophical Writings. Cambridge University Press. ISBN   9780521358125.
  5. Revonsuo, A., Consciousness: The Science of Subjectivity (Milton Park: Taylor & Francis, 2010), pp. 50–52.

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