Descartes I Think Therefore I Am Argument

Descartes Meditations

The skeptical arguments presented in Descartes’ first meditation are to suppose that one cannot know whether one is asleep or awake; that one cannot know whether one’s eyes, hands, body and surroundings are real; that one cannot know if two and three really do make five or if one is only being deceived. The main argument is that one may not trust one’s senses because one’s senses can deceive one. The argument proceeds in this manner: since one cannot tell if one is asleep or awake with any certainty, one has good reason to doubt all sense data.

Descartes proceeds, however, to develop the argument by identifying the causes of the present situation: one explanation is that God exists but permits man to be deceived; another explanation is that everything is a dream; a third explanation is that there is no good God but rather an evil demon that deceives man.

Descartes does not insist upon the dream argument for he notes that not everyone will accept it as rational. He then picks up the God argument but proceeds to conclude further on the Meditations that a good God cannot deceive. Thus, before closing out the first meditation he offers the third premise, which is the evil demon argument, suggesting that deception is the work of an evil thing.

Now that these arguments have been stated, and Descartes has no answer to any of them at the close of the first meditation, he proceeds from a standpoint of doubt. In this position, he regards nothing as certain. He will use the later meditations to show how he can move from doubt to certainty.

In the second meditation, Descartes posits that since doubt is all he can do he can at least declare with certainty that he is thinking—and the fact that he is thinking proves his existence; for something that does not exist cannot be said to have thoughts. This is how he arrives at the conclusion, “I think, therefore I am.” He means that because he is capable at least of having doubts, this capacity for doubt is proof of his existence. Even as he might choose to doubt the information conveyed him by his senses he cannot doubt that he is doubting—i.e., thinking. Therefore, he knows he exists. Thus, from doubt he moves to certainty about the existence at the very least of his mind. In this manner he also shows that it is easier to know the mind than it is to know the body, since knowledge of the mind is the first certainty one can have.

Now Descartes moves to the third meditation in which he declares that since he has an idea of a perfect God in his mind, God must exist. It is comparable to Anselm’s ontological proof for the existence of God—which is: “God is that than which nothing greater can be conceived.” Descartes points out that perfection and reality must be as much in the cause as in the effect. Since the idea of God represents something so perfect that he himself (or his own mind) could not be the cause of it (since he lacks perfection), God must exist in reality and be the cause of the idea of God in Descartes’ own mind.

His argument proceeds thus: he affirms he must inquire “whether there is a God, and, if there is, whether or not he can be a deceiver. For if I am ignorant of this, it appears I am never capable of being completely certain about anything else” (p. 25). After meditating on how he can know things by their effect, perceived through his senses, he then arrives at this question: “For whence, I ask, could an effect get its reality, if not from its cause? And how could the cause give that reality to the effect, unless it also possessed that reality?” (p. 28). He answers the question by stating that something cannot come from nothing. It is the first cause argument. By extension he asserts that what is more perfect cannot come into existence by what is less perfect. And thus he reasons that “If the objective reality of any of my ideas is found to be so great that I am certain that the same reality was not in me, either formally or eminently, and that therefore I myself cannot be the cause of the idea, then it necessarily follows that I am not alone in the world, but that something else, which is the cause of this idea, also exists” (p. 29). The fact that he can doubt his existence while having within himself an idea of perfection suggests that the reality of perfection preceded his existence and therefore had reality before he did. Then he makes this important observation which echoes Anselm’s argument: “For nothing more perfect than God, or even as perfect as God, can be thought or imagined. But if I got my being from myself, I would not doubt, nor would I desire, nor would I lack anything at all” (p. 32). And because he doubts, he knows he is imperfect, and that the perfect must exist outside himself. Thus he knows that God exists, and he arrives at this conclusion from the basis of his own doubting—which first proved that his mind exists. And he knows he is not deceived by God, since God must be perfect for him to have this idea of perfection, and “fraud and deception depend upon some defect” (p. 35).

Thus, Descartes has answered his objections: “I acknowledge that it is impossible for God ever to deceive me, for trickery or deception is always indicative of some imperfection” (p. 36). Then he goes on to assert that he is capable of making judgments thanks to the faculty of reason given him by God: “there is in me a certain faculty of judgment, which, like everything else that is in me, I undoubtedly received from God. And since he does not wish to deceive me, he assuredly has not given me the sort of faculty with which I could ever make a mistake, when I use it properly” (p. 36). And just because one can doubt the existence of other things, such as the body, one cannot doubt the existence of God.

In this manner, Descartes is able to remove the doubts from his first meditation in the later meditations. He knows that by doubting, he exists. He knows that of all his thoughts the one that could not have come from him is the thought of God’s perfection. Since he himself is imperfect (indicated by his own doubting), he cannot be said to be the cause of an idea of perfection. That cause of the idea of perfection must have come from some place other than himself—indeed, from perfection itself, since no imperfect thing can cause the idea of perfection. Thus, he reasons that God has touched his thought directly with the idea of His own perfection, and this is how one knows that God exists.