Cogito ergo sum

"Cogito, ergo sum" (Latin: "I am thinking, therefore I exist", or traditionally "I think, therefore I am") is a philosophical statement by René Descartes, which became a foundational element of Western rationalism. "Cogito ergo sum" is a translation of Descartes' original French statement: "Je pense, donc je suis", which occurs in his Discourse on Method (1637).

Although the idea expressed in "cogito ergo sum" is widely attributed to Descartes, many predecessors offer similar arguments —particularly Augustine of Hippo in De Civitate Dei (books XI, 26), who also anticipates modern refutations of the concept. (See Principles of Philosophy, §7: "Ac proinde haec cognitio, ego cogito, ergo sum, est omnium prima et certissima etc.").

Introduction

The phrase "cogito ergo sum" is not used in Descartes' most important work, the Meditations on First Philosophy, but the term "the cogito" is (often confusingly) used to refer to it. Descartes felt that this phrase, which he had used in his earlier Discourse, had been misleading in its implication that he was appealing to an inference, so he changed it to "I am, I exist" (also often called "the first certainty") in order to avoid the term "cogito".

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 has survived the doubt. In his belief in his own existence he finds it: it is impossible to doubt that he exists. Even if there were a deceiving god (or an evil demon, the tool he uses to stop himself sliding back into ungrounded beliefs), his belief in his own existence would be secure, for how could he be deceived unless he 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 thought anything at all then I certainly existed. But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving 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 two important notes to keep in mind here. First, he only claims 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 is not saying that his existence is necessary; he is saying that if he's thinking, then he necessarily exists (see the instantiation principle).

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 unshakeable." (AT VII 24; CSM II 16)

Perhaps what Descartes meant, simply put is "I am vividly aware of my existence".

Common errors

Some non-philosophers who first come across the cogito attempt to refute it in the following way. "I think, therefore I exist," they argue, can be reversed as "I do not think, therefore I do not exist." They argue that a rock does not think, but it still exists, which disproves Descartes' argument. However, this is the logical fallacy of denying the antecedent. The correct corollary by modus tollens is "I do not exist, therefore I do not think."

This fallacy and its prevalence is illustrated by the popular joke:

Descartes is sitting in a bar, having a drink. The bartender asks him if he would like another. "I think not," he says, and vanishes.

Criticisms of the cogito

There have been a number of criticisms of the cogito. The first of the two under scrutiny here concerns the nature of the step from "I am thinking" to "I exist". The contention is that this is a syllogistic inference, for it appears to require the extra premise: "Whatever has the property of thinking, exists", and that extra premise must surely have been rejected at an earlier stage of the doubt.

It could be argued that "Whatever has the property of thinking, exists" is self-evident, and thus not subject to the method of doubt. This is because it is true that any premise of the form: "Whatever has the property F, exists", but within the method of doubt, only the property of thinking is indubitably a property of the meditator. Descartes does not make use of this defence, however; as we have already seen, he responds to the criticism by conceding that there would indeed be an extra premise needed, but denying that the cogito is a syllogism.

Perhaps a more relevant contention is whether the 'I' to which Descartes refers is justified. In Descartes, The Project of Pure Enquiry Bernard Williams provides a history and full evaluation of this issue. The main objection, as presented by Georg Lichtenberg, 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.

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 relativising it to something. It seems at first as though this something needn't be a thinker, the "I", but Williams goes through each of the possibilities, demonstrating that none of them can do the job. He concludes that Descartes is justified in his formulation (though possibly without realising why that was so).

Williams's argument

Whilst the preceding two arguments against the cogito fail, other arguments have been advanced by 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 perspective; namely objective "thought-events" in the former case, and an objective thinker in the latter. The obvious problem is that, through introspection, or our experience of consciousness, we have no way of moving to conclude the existence of any third-personal fact, verification of which would require a thought necessarily impossible, being, as Descartes is, bound to the evidence of his own consciousness alone.

References

Quotations from Descartes' work use the standard form: first a reference to the twelve-volume edition of Descartes' works by Adam and Tannery (abbreviated "AT"), followed by a reference to the three-volume English edition translated by John Cottingham, Robert Stoothoff, Dugald Murdoch, and (in vol. III) Anthony Kenny (abbreviated "CSM" for volumes I and II, "CSMK" for volume III).

External links

Descartes and Language: What is the Cogito?

Epistemology | Latin philosophical phrases

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