Stripped of every belief that could conceivably be doubted, adrift in a sea of seemingly bottomless uncertainty, Descartes desperately casts about for some foothold—some firm ground on which to rebuild the edifice of human knowledge …
“I noticed that while I was trying to think everything false, it was necessary that I, who was thinking this, was something. And observing that this truth, ‘I am thinking, therefore I exist’ [cogito ergo sum], was so firm and sure that all the most extravagant suppositions of the skeptics were incapable of shaking it, I decided that I could accept it without scruple as the first principle of the philosophy I was seeking.”
And so came the Frenchman René Descartes to think what is certainly the most famous and probably the most influential thought in the history of Western philosophy.
“Je pense, donc je suis.”
René Descartes, 1637
The method of doubt Descartes was himself at the vanguard of the scientific revolution sweeping through Europe in the 17th century, and it was his ambitious plan to cast aside the tired dogmas of the medieval world and to “establish the sciences” on the firmest of foundations. To this end he adopted his rigorous “method of doubt.” Not content to pick out the odd rotten apple (to use his own metaphor), he empties the barrel completely, discarding any belief that is open to the slightest degree of doubt. In a final twist, he imagines an evil demon intent only on deceiving him, so that even the apparently self-evident truths of geometry and mathematics are no longer certain.
It is at this point—stripped of everything, even his own body and senses, other people, the entire world outside him—that Descartes finds salvation in the cogito. However deluded he may be, however determined the demon to deceive him at every turn, there has to be someone or something to be deluded, someone or something to be deceived. Even if he is mistaken about everything else, he cannot doubt that he is there, at that moment, to think the thought that he may be thus mistaken. The demon “will never bring it about that I am nothing so long as I think that I am something … I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind.”
The well-known Latin form—cogito ergo sum—is found in Descartes’s Principles of Philosophy (1644), but in his Discourse on the Method (1637) the French version occurs (je pense, donc je suis) and in his most important work, Meditations, it does not appear in its canonical form at all. The traditional English translation—“I think, therefore I am”—is unhelpful in that the force of the argument is only brought out by the continuous form of the present tense, so in philosophical contexts it is often rendered “I am thinking, therefore I exist.”
The limits of the cogito An early criticism of Descartes, taken up by many since, is that he infers too much from the cogito—that he is only entitled to the conclusion that there is thinking going on, not that it is he that is doing the thinking. But even if we concede that thoughts do indeed presuppose thinkers, it must be admitted that what Descartes’s insight establishes is very limited. First, the cogito is essentially first-personal—my cogito only works for me, yours only for you: it is certainly not beyond the demon’s powers to fool me into thinking that you are thinking (and therefore that you exist). Second, the cogito is essentially present-tense: it is perfectly compatible with it that I cease to exist when I am not thinking. Third, the “I” whose existence is established is extremely attenuated and elusive: I may have none of the biography and other attributes that I believe make me me, and indeed I may still be completely in the clutches of the deceiving demon.
In sum, the “I” of the cogito is a bare instant of self-consciousness, a mere pinprick cut off from everything else, including its own past. So what can Descartes establish on so precarious a foundation?
Cogito ergo sum may be the best known of all philosophical sayings, but its precise origins are not entirely clear. Although it is inextricably linked to Descartes, the idea behind the cogito goes back well before his time. At the beginning of the fifth century AD, for instance, St. Augustine wrote that we can doubt anything but the soul’s own doubting, and the idea did not originate with him.
Reconstructing knowledge Descartes may have dug down to bedrock, but has he left himself any materials to start rebuilding? He seems to have set the bar impossibly high—nothing less than demon-proof certainty will do. As it turns out, the return journey is surprisingly (perhaps alarmingly) rapid. There are two main supports to Descartes’s theory of knowledge. First he notes that a distinctive feature of the cogito is the clarity with which we can see that it must be so, and from this he concludes that there is a general rule “that the things we conceive very clearly and very distinctly are all true.” And how can we be sure of this? Because the clearest and most distinct idea of all is our idea of a perfect, all-powerful, all-knowing God.
God is the source of all our ideas, and since he is good, he will not deceive us; the use of our powers of observation and reason (which also come from God) will accordingly lead us to truth, not falsehood. With the arrival of God, the seas of doubt very quickly recede—the world is restored and the task of reconstructing our knowledge on a sound, scientific basis can begin.
“… to have recourse to the veracity of the supreme Being, in order to prove the veracity of our senses, is surely making a very unexpected circuit.”
David Hume, 1748
Lingering doubts Very few have been convinced by Descartes’s attempt to climb out of the skeptical hole that he had dug for himself. Much attention has focused on the infamous “Cartesian circle”—the apparent use of clear and distinct ideas to prove the existence of God, whose goodness then warrants our use of clear and distinct ideas. Whatever the force of this argument (and it is far from clear that Descartes in fact fell into so obvious a trap), it is hard to share his confidence that he has successfully exorcized the demon. Descartes cannot (and does not) deny the fact that deception does occur; and if we follow his general rule, that must mean that we can sometimes be mistaken in thinking that we have a clear and distinct idea of something. But obviously we cannot know that we are making such a mistake, and if we cannot identify such cases, the door is once again wide open to skepticism.
Descartes has been called the father of modern philosophy. He has a good claim to the title, but not quite for the reasons that he would have wished. His aim was to dispel skeptical doubts once and for all, so that we could confidently dedicate ourselves to the rational pursuit of knowledge, but in the end he was much more successful at raising such doubts than quelling them. Subsequent generations of philosophers have been transfixed by the issue of skepticism, which has been at or near the top of the philosophical agenda from the day that Descartes put it there.
the condensed idea
I am thinking therefore I exist
| Timeline | |
|---|---|
| AD1637 | The mind-body problem |
| 1644 | Cogito ergo sum |
| 1690 | The veil of perception |
| 1981 | The brain in a vat |