Descartes' Meditations: From Doubt to God's Existence

The Skeptical Arguments of the First Meditation

The skeptical arguments presented in Descartes' First Meditation ask us 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; and that one cannot know if two and three really do make five, or whether one is simply being deceived. The main argument is that one may not trust one's senses, because the senses can deceive. The argument proceeds as follows: since one cannot determine with any certainty whether one is asleep or awake, one has good reason to doubt all sense data.

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

Descartes does not insist upon the dream argument, noting that not everyone will accept it as rational. He then takes up the God argument, but proceeds to conclude in the later meditations that a good God cannot deceive. Before closing the First Meditation, therefore, he offers a third premise — 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, and he will use the later meditations to show how he can move from doubt to certainty.

From Doubt to Certainty: The Cogito

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 of having doubts, that very capacity for doubt is proof of his existence. Even as he might choose to doubt the information conveyed to him by his senses, he cannot doubt that he is doubting — that is, thinking. Therefore, he knows he exists.

Thus, from doubt, he moves to certainty about the existence of at least his own mind. In this manner he also shows that it is easier to know the mind than to know the body, since knowledge of the mind is the first certainty one can have.

The Causal Argument for God's Existence

Descartes moves next to the Third Meditation, in which he declares that since he has an idea of a perfect God in his mind, God must exist. This is comparable to Anselm's ontological proof for the existence of God: "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 (given that he lacks perfection), God must exist in reality and be the cause of the idea of God within Descartes' own mind.

His argument proceeds as follows: he affirms that 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 effects, perceived through the senses, he arrives at the 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 by stating that something cannot come from nothing — the first cause argument. By extension, he asserts that what is more perfect cannot come into existence through what is less perfect.

He thus 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 own 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. He then makes the following important observation, echoing 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). Because he doubts, he knows he is imperfect, and that the perfect must therefore exist outside himself. He thus arrives at the conclusion that God exists — and he reaches this conclusion from the very basis of his own doubting, which first proved that his mind exists. He further knows he is not deceived by God, since God must be perfect for him to possess this idea of perfection, and "fraud and deception depend upon some defect" (p. 35).

Works Cited

Descartes, R. Meditations on First Philosophy. Hackett Publishing, 1993.