is a philosophical
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
statement proposed by . The simple meaning of the phrase is that someone wondering whether or not they exist is, in and of itself, proof that something, an "I", exists to do the thinking — However this "I" is not the more or less permanent person we call "I". It may be that the something that thinks is purely momentary, and not the same as the something which has a different thought the next moment.
The phrase became a fundamental element of Western philosophy
Western philosophy is the philosophical thought and work of the Western or Occidental world, as distinct from Eastern or Oriental philosophies and the varieties of indigenous philosophies....
, as it was perceived to form a foundation for all knowledge. While other knowledge could be a figment of imagination, deception or mistake, the very act of doubting one's own existence serves to some people as proof of the reality of one's own existence, or at least that of one's thought.
The statement is sometimes given as
(English: "I doubt, therefore I think, therefore I am"), although this extension was never used by Descartes himself and it is potentially misleading, as it suggests that Descartes' argument is based on doubt, whereas it is inherent in any mental activity whatsoever.
A common mistake is that people take the statement as proof that they, as a human person, exist. However, it is a severely limited conclusion that does nothing to prove that one's own body exists, let alone anything else that is perceived in the physical universe. It only proves that one's mind exists (that part of an individual that observes oneself doing the doubting). It does not rule out other possibilities, such as waking up to find oneself to be a butterfly who had dreamed of having lived a human life.
Descartes's original statement was from his Discourse on Method
The Discourse on the Method is a philosophical and autobiographical treatise published by René Descartes in 1637. Its full name is Discourse on the Method of Rightly Conducting One's Reason and of Seeking Truth in the Sciences .The Discourse on Method is best known...
(1637). He wrote it in French
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
, not in Latin and thereby reached a wider audience in his country than that of scholars. He uses the Latin "Cogito ergo sum" in the later Principles of Philosophy
Principles of Philosophy is a book by René Descartes. Written in Latin, it was published in 1644 and dedicated to Elisabeth of Bohemia, with whom Descartes had a long standing friendship. A French version followed in 1647. It set forth the principles of nature—the Laws of Physics--as Descartes...
(1644), Part 1, article 7: "" (English
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
: "This proposition, I think, therefore I am
, is the first and the most certain which presents itself to whoever conducts his thoughts in order."). At that time, the argument had become popularly known in the English speaking world as 'the "" argument,' which is usually shortened to "" when referring to the principle virtually everywhere else.
The phrase Cogito ergo sum
is not used in Descartes' Meditations on First Philosophy
Meditations on First Philosophy is a philosophical treatise written by René Descartes and first published in 1641 . The French translation was published in 1647 as Méditations Metaphysiques...
but the term "the cogito
" is (often confusingly) used to refer to an argument from it. In the Meditations, Descartes phrases the conclusion of the argument as "that the proposition, I am, I exist,
is necessarily true whenever it is put forward by me or conceived in my mind." (Meditation
At the beginning of the second meditation, having reached what he considers to be the ultimate level of doubt — his argument from the existence of a deceiving god — Descartes examines his beliefs to see if any have survived the doubt. In his belief in his own existence, he finds that it is impossible to doubt that he exists. Even if there were a deceiving god (or an evil demon), one's belief in their own existence would be secure, for how could one be deceived unless one existed in order to be deceived?
But I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I, too, do not exist? No. If I convinced myself of something [or thought anything at all], then I certainly existed. But there is a deceiver of supreme power and cunning who deliberately and constantly deceives me. In that case, I, too, undoubtedly exist, if he deceives me; and let him deceive me as much as he can, he will never bring it about that I am nothing, so long as I think that I am something. So, after considering everything very thoroughly, I must finally conclude that the proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind. (AT VII 25; CSM II 16–17)
There are three important notes to keep in mind here. First, he claims only the certainty of his own
existence from the first-person point of view — he has not proved the existence of other minds at this point. This is something that has to be thought through by each of us for ourselves, as we follow the course of the meditations. Second, he does not say that his existence is necessary; he says that if he thinks
, then necessarily he exists (see the instantiation principle
The "Principle of Instantiation" or "Principle of Exemplification" is a thesis in philosophy that states that there can be no uninstantiated or unexemplified properties . In other words, it is impossible for a property to exist which is not had by some object. Aristotle is well-known for...
). Third, this proposition "I am, I exist" is held true not based on a deduction (as mentioned above) or on empirical induction but on the clarity and self-evidence of the proposition.
Descartes does not use this first certainty, the cogito
, as a foundation upon which to build further knowledge; rather, it is the firm ground upon which he can stand as he works to restore his beliefs. As he puts it:
Archimedes used to demand just one firm and immovable point in order to shift the entire earth; so I too can hope for great things if I manage to find just one thing, however slight, that is certain and unshakable. (AT VII 24; CSM II 16)
According to many of Descartes' specialists, including Étienne Gilson
Étienne Gilson was a French Thomistic philosopher and historian of philosophy...
, the goal of Descartes in establishing this first truth is to demonstrate the capacity of his criterion — the immediate clarity and distinctiveness of self-evident propositions — to establish true and justified propositions despite having adopted a method of generalized doubt. As a consequence of this demonstration, Descartes considers science and mathematics to be justified to the extent that their proposals are established on a similarly immediate clarity, distinctiveness, and self-evidence that presents itself to the mind. The originality of Descartes' thinking, therefore, is not so much in expressing the cogito — a feat accomplished by other predecessors, as we shall see — but on using the cogito as demonstrating the most fundamental epistemological principle, that science and mathematics are justified by relying on clarity, distinctiveness, and self-evidence.
Baruch de Spinoza and later Benedict de Spinoza was a Dutch Jewish philosopher. Revealing considerable scientific aptitude, the breadth and importance of Spinoza's work was not fully realized until years after his death...
in "Principia philosophiae cartesianae
Principia philosophiae cartesianae or Renati Descartes Principia Philosophiae, More Germetrico Demonstrata is a philosophical work of Baruch Spinoza published in Amsterdam in 1663 including its appendix, Cogitata Metaphisica...
" at its Prolegomenon
identified "cogito ergo sum" the "ego sum cogitans
" (I am a thinking being) as the thinking substance
Substance may refer to:*Chemical substance, a material with a definite chemical composition*Drug substance*Matter, the substance of which all physical objects are made*Substance theory, theory positing that a substance is distinct from its properties....
with his ontological
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...
interpretation. It can also be considered that Cogito ergo sum
is needed before any living being can go further in life".
Although the idea expressed in Cogito ergo sum
is widely attributed to Descartes, he was not the first to mention it. Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...
spoke about the "knowledge of knowledge" (Greek νόησις νοήσεως
- nóesis noéseos
) and Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
explains the idea in full length:
But if life itself is good and pleasant (...) and if one who sees is conscious that he sees, one who hears that he hears, one who walks that he walks and similarly for all the other human activities there is a faculty that is conscious of their exercise, so that whenever we perceive, we are conscious that we perceive, and whenever we think, we are conscious that we think, and to be conscious that we are perceiving or thinking is to be conscious that we exist... (Nicomachean Ethics
Augustine of Hippo
The Nicomachean Ethics is the name normally given to Aristotle's best known work on ethics. The English version of the title derives from Greek Ἠθικὰ Νικομάχεια, transliterated Ethika Nikomacheia, which is sometimes also given in the genitive form as Ἠθικῶν Νικομαχείων, Ethikōn Nikomacheiōn...
, 1170a25 ff.)
Augustine of Hippo , also known as Augustine, St. Augustine, St. Austin, St. Augoustinos, Blessed Augustine, or St. Augustine the Blessed, was Bishop of Hippo Regius . He was a Latin-speaking philosopher and theologian who lived in the Roman Africa Province...
in De Civitate Dei
writes Si […] fallor, sum
("If I am mistaken, I am") (book XI, 26), and also anticipates modern refutations of the concept. Furthermore, in the Enchiridion
Augustine attempts to refute skepticism
Skepticism has many definitions, but generally refers to any questioning attitude towards knowledge, facts, or opinions/beliefs stated as facts, or doubt regarding claims that are taken for granted elsewhere...
by stating, "[B]y not positively affirming that they are alive, the skeptics ward off the appearance of error in themselves, yet they do make errors simply by showing themselves alive; one cannot err who is not alive. That we live is therefore not only true, but it is altogether certain as well" (Chapter 7 section 20). Another predecessor was Avicenna
Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā , commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived...
's "Floating Man" thought experiment
A thought experiment or Gedankenexperiment considers some hypothesis, theory, or principle for the purpose of thinking through its consequences...
on human self-awareness
Self-awareness is the capacity for introspection and the ability to reconcile oneself as an individual separate from the environment and other individuals...
Self-consciousness is an acute sense of self-awareness. It is a preoccupation with oneself, as opposed to the philosophical state of self-awareness, which is the awareness that one exists as an individual being; although some writers use both terms interchangeably or synonymously...
There have been a number of criticisms of the argument. One concerns the nature of the step from "I am thinking" to "I exist." The contention is that this is a syllogistic
A syllogism is a kind of logical argument in which one proposition is inferred from two or more others of a certain form...
inference, for it appears to require the extra premise
Premise can refer to:* Premise, a claim that is a reason for, or an objection against, some other claim as part of an argument...
: "Whatever has the property of thinking, exists", a premise Descartes did not justify. In fact, he conceded that there would indeed be an extra premise needed, but denied that the cogito
is a syllogism (see below).
To argue that the cogito
is not a syllogism, one may call it self-evident that "Whatever has the property of thinking, exists". In plain English, it seems incoherent to actually doubt that one exists and is doubting. Strict skeptics maintain that only the property of 'thinking' is indubitably a property of the meditator (presumably, they imagine it possible that a thing thinks but does not exist). This counter-criticism is similar to the ideas of
Kaarlo Jaakko Juhani Hintikka is a Finnish philosopher and logician.Hintikka was born in Vantaa. After teaching for a number of years at Florida State University, Stanford, University of Helsinki, and the Academy of Finland, he is currently Professor of Philosophy at Boston University...
, who offers a non-syllogistic interpretation of Cogito Ergo Sum. He claimed that one simply cannot doubt the proposition "I exist". To be mistaken about the proposition would mean something impossible: I do not exist, but I am still wrong.
Perhaps a more relevant contention is whether the "I" to which Descartes refers is justified.
In Descartes, The Project of Pure Enquiry
, Bernard Williams
Sir Bernard Arthur Owen Williams was an English moral philosopher, described by The Times as the most brilliant and most important British moral philosopher of his time. His publications include Problems of the Self , Moral Luck , Ethics and the Limits of Philosophy , and Truth and Truthfulness...
provides a history and full evaluation of this issue. Apparently, the first scholar who raised the problem was Pierre Gassendi
Pierre Gassendi was a French philosopher, priest, scientist, astronomer, and mathematician. With a church position in south-east France, he also spent much time in Paris, where he was a leader of a group of free-thinking intellectuals. He was also an active observational scientist, publishing the...
. He points out that recognition that one has a set of thoughts does not imply that one is a particular thinker or another. Were we to move from the observation that there is thinking occurring to the attribution of this thinking to a particular agent, we would simply assume what we set out to prove, namely, that there exists a particular person endowed with the capacity for thought
. In other words, the only claim that is indubitable here is the agent-independent claim that there is cognitive activity present
The objection, as presented by Georg Lichtenberg
Georg Christoph Lichtenberg was a German scientist, satirist and Anglophile. As a scientist, he was the first to hold a professorship explicitly dedicated to experimental physics in Germany...
, is that rather than supposing an entity that is thinking, Descartes should have said: "thinking is occurring." That is, whatever the force of the cogito
, Descartes draws too much from it; the existence of a thinking thing, the reference of the "I," is more than the cogito
can justify. Friedrich Nietzsche
Friedrich Wilhelm Nietzsche was a 19th-century German philosopher, poet, composer and classical philologist...
criticized the phrase in that it presupposes that there is an "I", that there is such an activity as "thinking", and that "I" know what "thinking" is. He suggested a more appropriate phrase would be "it thinks." In other words the "I" in "I think" could be similar to the "It" in "It is raining." David Hume
David Hume was a Scottish philosopher, historian, economist, and essayist, known especially for his philosophical empiricism and skepticism. He was one of the most important figures in the history of Western philosophy and the Scottish Enlightenment...
is another philosopher who criticizes Descartes 'Cogito Ergo Sum'. He says that those philosophers who argue that we can work out we have a 'self' using reason are confusing 'similarity' with 'identity'. He is saying that the similarity of our thoughts and the continuity of them in this similarity does not mean that we can identify ourselves as a self but that our thoughts are similar.
Williams' argument in detail
In addition to the preceding two arguments against the cogito
, other arguments have been advanced by Bernard Williams. He claims, for example, that what we are dealing with when we talk of thought, or when we say "I am thinking," is something conceivable from a third-person
Grammatical person, in linguistics, is deictic reference to a participant in an event; such as the speaker, the addressee, or others. Grammatical person typically defines a language's set of personal pronouns...
perspective; namely objective "thought-events" in the former case, and an objective
Objectivity is a central philosophical concept which has been variously defined by sources. A proposition is generally considered to be objectively true when its truth conditions are met and are "mind-independent"—that is, not met by the judgment of a conscious entity or subject.- Objectivism...
thinker in the latter.
Williams provides a meticulous and exhaustive examination of this objection. He argues, first, that it is impossible to make sense of "there is thinking" without relativizing it to something.
However, this something cannot be Cartesian egos, because it is impossible to differentiate objectively between things just on the basis of the pure content of consciousness.
The obvious problem is that, through introspection
Introspection is the self-observation and reporting of conscious inner thoughts, desires and sensations. It is a conscious and purposive process relying on thinking, reasoning, and examining one's own thoughts, feelings, and, in more spiritual cases, one's soul...
, or our experience of consciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
, we have no way of moving to conclude the existence of any third-personal fact, to conceive of which would require something above and beyond just the purely subjective contents of the mind.
Søren Kierkegaard's critique
The Danish philosopher Søren Kierkegaard provided a critical response to the cogito. Kierkegaard argues that the cogito already pre-supposes the existence of "I", and therefore concluding with existence is logically trivial. Kierkegaard's argument can be made clearer if one extracts the premise "I think" into two further premises:
I am that "x"
Therefore I think
Therefore I am
Where "x" is used as a placeholder in order to disambiguate the "I" from the thinking thing.
Here, the cogito has already assumed the "I"'s existence as that which thinks. For Kierkegaard, Descartes is merely "developing the content of a concept", namely that the "I", which already exists, thinks.
Kierkegaard argues that the value of the cogito is not its logical argument, but its psychological
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...
appeal: a thought must have something that exists to think the thought. It is psychologically difficult to think "I do not exist". But as Kierkegaard argues, the proper logical flow of argument is that existence is already assumed or pre-supposed in order for thinking to occur, not that existence is concluded from that thinking.
- W.E. Abraham, "Disentangling the Cogito", Mind 83:329 (1974)
- Z. Boufoy-Bastick, Introducing 'Applicable Knowledge' as a Challenge to the Attainment of Absolute Knowledge , Sophia Journal of Philosophy, VIII (2005), pp 39–52.
- R. Descartes (translated by John Cottingham), Meditations on First Philosophy, in The Philosophical Writings of Descartes vol. II (edited Cottingham, Stoothoff, and Murdoch; Cambridge University Press, 1984) ISBN 0-521-28808-8
- G. Hatfield, Routledge Philosophy Guidebook to Descartes and the Meditations (Routledge, 2003) ISBN 0-415-11192-7
- S. Kierkegaard, Concluding Unscientific Postscript (Princeton, 1985) ISBN 978-0-691-02081-5
- S. Kierkegaard, Philosophical Fragments (Princeton, 1985) ISBN 978-0-69-102036-5
- B. Williams, Descartes, The Project of Pure Enquiry (Penguin, 1978)