Summary of Descartes Meditations on First Philosophy (I-III)

Descartes' Meditations on First Philosophy is taught canonically in universities today, and for good reason: Descartes was one of the first major Western philosophers to attempt to construct a foundation of certainty about knowledge. Divided into six books, Meditations covers a wide range of epistemic and metaphysical issues, aimed at giving certain answers to questions about existence, the senses, and God. The first three "meditations" are the most commonly taught in introductory philosophy courses, so it is useful for any philosophy student to survey the key issues addressed in them.

In Meditation One, Descartes discusses how as a child he believed many false things. Descartes asserts that those false beliefs have to be eliminated before he can obtain any true knowledge. He goes on to explain that he does not exactly have to prove his beliefs to be false, but he needs to convince himself to avoid having beliefs that are not certain. He holds that he can find some doubt in every one of his false beliefs. What he has heretofore accepted as the truth he has learned from his senses, and senses can often deceive. Although he believes that his senses can and do deceive him, there are still things that he is unable to doubt, even though they were learned with those senses. He considers the example of him sitting in front of the fire, touching paper, and wearing his gown. At first he implies that there is no way to deny that he is actually feeling those things, and he knows that from his senses. He then wonders if he is dreaming, because in a dream one would be thinking that you were feeling those things, but in reality one would not be.

Descartes also questions God and his own existence. He wonders if God only makes it seem to him that he is on Earth and that there is a sky. He wonders if God is deceiving him in this way. To him, the accepting the possibility of deception is useful. He ponders whether the "sky, air, earth, color, shape, sound and other external things are just dreamed illusions" He suggests that he doesn't have his senses, he has no eyes, ears, or anything, that they are just false beliefs of his.

In Meditation Two, Descartes begins to have doubtful thoughts that he can not ignore. Everything he sees is unreal, and he considers the possibility that the only truth is that nothing is certain. He tries to figure out what he "is." He answers himself by saying he is a "man, of course," he then questions what a man actually is. He couldn't say man was an animal, because then he would have to question what an animal was. Descartes perpetually refers to himself as having no body or basically having any tangible existence. He says that he is still something, but isn't sure if that something that he is actually exists.

Descartes considers a piece of wax and what can be known about it through the senses: shape, color, taste, smell, etc. When placed near a fire, all of the sensible qualities of the wax change, yet the same piece of wax remains, so we do not come to know the wax through the senses. Because there are an infinite number of possibilities as to the potential things that piece of wax might become, the imagination can not be responsible for our knowing the wax. Hence, Descartes concludes, we only come to know the wax through the intellect.

Later, he puts forward the "evil genius" hypothesis: that there is some powerful deceiver who tricks our senses to give us false images, impressions, and so forth. With this evil deceiver at work, we could not possibly know anything through the senses. However, Descartes argues that the possibility of being deceived requires something with perception-there must be an object of the deception. Since our senses did not provide us with that idea, it must have been the product of our intellect. Thus, through the intellect, we come to know the existence of the self, just as we-a few logical steps later-come to know the wax.

In Meditation Three, Descartes raises questions about the existence of God. He plugs his ears, closes his eyes, and stops using all of his senses. He tries to rid his thoughts of physical objects. With everything shut off around him, he looks within himself, to try to get to know himself better. He still wonders if God is deceiving him, but eventually concludes that he has no reason to believe that God would deceive, as God is perfect and hence all-good. This is closely related to Descartes' ontological argument, which he states as follows:

[1] But if the mere fact that I can produce from my thought the idea of something entails that everything which I clearly and distinctly perceive to belong to that thing really does belong to it, is not this a possible basis for another argument to prove the existence of God? Certainly, the idea of God, or a supremely perfect being, is one that I find within me just as surely as the idea of any shape or number. And my understanding that it belongs to his nature that he always exists is no less clear and distinct than is the case when I prove of any shape or number that some property belongs to its nature.

Here, Descartes is attempting to show that God's existence is as self-evident as a mathematical truth, through appealing to everyday reasoning. He employs the classical distinction between essence and existence to his advantage here: by saying that perfection is part of God's essence, with existence being a part of perfection, he then believes it reasonable to conclude that God exists.

Cottingham, John, Robert Stoothoff, Dugald Murdoch, and (for vol. 3) Anthony Kenny, eds. and trans. 1984. The Philosophical Writings of Descartes, vols. 1-3. p. 45. Cambridge: Cambridge University Press.