Meditations on First Philosophy begins with two introductions. The first is addressed to the theology faculty at the Sorbonne (a university in Paris), the second to his lay readers. He outlines some of the objections to the Discourse and asserts that his critics generally ignored his chains of logic and only attacked his conclusions. He pledges to return to the two criticisms he finds worth considering. He asks his readers to approach the rest of the book with an unbiased mind.
The first meditation reiterates material from the Discourse. Responding to an objection to his critique of the senses, Descartes agrees that he would seem a madman if he argued he was not sure that he possessed a body. But he also points out that in his dreams he experiences a reality as convincing as his waking reality. He can find no sure way to distinguish between waking life and sleep. He then goes on to argue that if we dream of hands, feet, eyes, and bodies, then they must actually exist. When we dream, he continues, we use information we gathered from reality. Even if particular complex objects do not exist, at least the basic colors and shapes that compose them exist. In the same way, we can say the physical sciences are uncertain because they study composites. Arithmetic and geometry study simple objects (shapes, angles, numbers) and are therefore trustworthy. He trusts his perceptions of self-evident truths such as simple shapes and numbers because he believes in an all-powerful God that created these things.
Descartes admits that he cannot be sure that God is not playing some sort of trick on him. However, because he believes that God is good, he knows that God would not deliberately deceive him. Therefore, to rebuild his knowledge on the basis of doubt, he decides to pretend that a “malignant demon” is bent on tricking him. This powerful demon has created the illusions of the physical world to deceive him. With this in mind, Descartes sets out to prove, using only reason, that some things are beyond doubt.
Most of meditation II is devoted to discovering whether there is anything about which Descartes can be absolutely certain. First he decides he can be certain that he exists, because if he doubts, there must be a thinking mind to do the doubting. He does not yet accept that he is a thinking mind inside a body. After all, the demon could have convinced him that his body and the physical world exist. He moves to another question: what is the “I” that is doing the thinking?
The answer is that the mind is a purely thinking thing. Descartes concedes, however, that though what he perceives with his senses may be false, he cannot deny that he perceives. So the human mind is capable of both thought and perception. He explains this using the example of a piece of wax. We understand that solid wax and wax melted by a candle are both wax. Therefore perception is not strictly a function of the senses. It must be the reasoning mind that makes this judgment. Because the senses can be deceived, physical objects, including bodies, are properly perceived only by the intellect, and the mind is still the only thing he can be certain exists.
In meditation III, Descartes says he can be certain that perception and imagination exist, because they exist in his mind as “modes of consciousness,” but he can never be sure whether what he perceives or imagines has any basis in truth. He then expands on his argument for the existence of God from the Discourse. He examines his own mind to see whether there is anything in him that would allow him to make God up. Not only is God perfect, but God is also infinite and all powerful. Descartes knows that he himself is finite. He reasons that it is not possible for a finite being to dream of infinity. Therefore the idea of the infinite must come before the idea of the finite, before any person can begin to think of what he or she is.
Meditation IV deals almost entirely with the nature and origin of truth and error. Descartes asserts that knowledge of God will lead us to knowledge of other things. Because God is perfect, it is impossible that God would deceive Descartes, because deception is an imperfection. But Descartes knows himself to be capable of error, and so he has to examine the nature of his own ability to err. He concludes that God must have created him so that he could be wrong. Imperfect things, like him, may occupy their place in the world perfectly. In other words, Descartes’ imperfections may be what make him perfect for his role in God’s plan. He further reasons that his own propensity to err must be his own failure to use his method to approach the knowledge sent to him by God.
Descartes decides in meditation V to begin to examine whether he can believe in the material world by examining the essence of material things in relation to God. He looks at his own ideas about the material world and separates them into two categories: distinct and confused. Mathematical ideas are distinct and therefore exist. He further concludes that no truth, no science, and no certitude can exist without the knowledge of the existence of God. He realizes that the existence of everything depends on God and reasons on that basis that he doesn’t have to doubt everything anymore. Descartes knows that God has given him the capacity to learn the truth about both intellectual and corporeal things.
Meditation VI is devoted to investigating whether material things exist. Finally, Descartes finds that it seems safe to believe that his God-given senses convey the truth to him. Above all, his senses convey to him that he has a body. He maintains that, though there is some mysterious link by which the mind is joined to the body, the mind and body are different things, and the mind will outlive the body. Having decided this, Descartes dismisses all his doubts of the past and determines, at last, that he can trust his senses.
In the first introduction, to the theologians of the Sorbonne, Descartes takes pains to avoid charges of heresy. He had already seen, in the case of Galileo, what could happen if the church disapproved of scholarly work. Although Descartes ultimately comes to conclusions that would be acceptable to the theologians—God exists; the human soul is eternal—it might have been considered heretical to feel that it was even necessary to logically prove God’s existence. The Catholic Church, after all, considers God’s existence to be a matter of fundamental, unquestionable truth. The introduction to the reader reiterates his intention of publishing for an audience of logically thinking but uneducated readers.
One way in which Descartes tried to make his work acceptable to a conservative Catholic audience was to structure the meditations in a form similar to that of the Spiritual Exercises of St. Ignatius of Loyola, the founder of the Jesuit Order. The Spiritual Exercises recommends a six-step path in which the Christian begins by releasing all attachment to the material world, but after gaining confidence in God, the Christian returns to the material world with a renewed sense of purpose. Descartes’ purpose was radically different, but the Meditations follow a sixfold structure that is, on the surface, similar. The first meditation proves that all things are subject to doubt. The second asserts that if we doubt, there must be a mind to do the doubting. The third meditation concerns Descartes’ proof of the existence of God. In the fourth, he explains how to distinguish what is true from what is false. In the fifth, he explains corporeal nature and further proves the existence of God. In the sixth, Descartes explains the difference between understanding and imagination and proves that the human mind is distinct from the body. As with the Spiritual Exercises, the steps go from detachment from the material world to establishing confidence in God to the achievement of confidence in the existence of the material world.
The three arguments that Descartes uses to make us doubt our own knowledge—the Dream argument, the Deceiving God argument, and the Evil Demon argument—are not meant to be taken literally. To prove anything beyond a shadow of a doubt, Descartes has to call everything into doubt. This strain of thinking in philosophy is called skepticism, the practice of critically examining one’s own knowledge and perception to determine whether they are true. But skeptics also have to ask whether there is such a thing as true knowledge—in other words, whether it is possible to know anything for certain. Descartes was not the first person to employ skepticism—the tradition reaches back as far as the history of philosophy.
Descartes hopes to come to one irrefutable truth on which he can build his philosophy. The truth that he eventually comes to is often called the “cogito argument,” after Descartes’ triumphant declaration in Discourse on the Method, Cogito ergo sum. Through this argument, he decides that he is a “thing that thinks.” In doing so, he reasons that we can only be certain of our minds and cannot be certain of our bodies’ existence.
With the wax argument, Descartes advances a new conception of the mind and its properties. Aristotle had held that the mind is only intellect and that sensation and imagination are properties of the body. Descartes insists that sensation and imagination, though they involve the body, are actually properties of the mind. Although we receive information through our senses when looking at unmelted wax and melted wax, neither our senses nor our imagination can tell us that both of these things are wax or that the wax started out unmelted and ended up melted. Only intellect can make that judgment. Without intellect, our perceptions and imaginings are meaningless and tell us nothing about the world.
The arguments expressed in meditation III are often called, derogatorily, “the Cartesian Circle.” Descartes argues that realizations such as Cogito ergo sum are “clear and distinct perceptions” and therefore certain. Essentially, Descartes claims that such perceptions are true because they are clear and distinct, and they are clear and distinct because it is obvious that they are true. This is called circular logic, and Descartes doesn’t want to be caught in this circle. He therefore attempts to legitimize all clear and distinct truths by claiming they are provided by God.
If God exists, then truth is possible, since God is truth and perfection. But Descartes attempts to prove that God exists by relying on his own clear and distinct perception of God’s existence. He is arguing that it is possible to have clear and distinct perception because we know that God exists and that we know that God exists because we have a clear and distinct perception of his existence. This logic is, again, circular. Descartes attempts to bolster this argument by saying that the idea of perfection, or God, must come from something outside of his own imperfect mind. He reasons that perfection must come from one source, and that source must be the perfect, all-powerful God. This argument has never held much philosophical weight, and it is tempting to see it as merely the result of caution on Descartes’ part about going too far with his doubt and exposing himself to censure.
Descartes’ idea that God can’t deceive us because God is good comes from ancient Greek ideas of virtue and truth, specifically from Plato. In this scheme, truth, existence, and virtue are inextricably linked. Good things are true and real, and bad things are unreal and false. Since God exists infinitely (the ultimate reality), we know that God cannot participate in deception. If Descartes makes mistakes, then it must be somehow helpful to the universe for mistakes to exist. Otherwise, they would not be allowed. A page torn from a book of poetry might seem meaningless, but when the page is in the book, the book as a whole makes sense.
Descartes makes an important distinction between the intellect and the human will. The intellect, crafted by God, is the source of understanding, sensation, and imagination. The will is our ability to either affirm or deny what our intellect tells us. If the will affirms something that is not true with the information the intellect delivers, then the will is always at fault, not the intellect. The difficulty lies in discerning when the will has made a mistake. Descartes, therefore, returns to the idea that we can only know what is true if we have had a clear and distinct perception. If we resolve to only ever believe what we have proved to ourselves, then we will be able to distinguish between what is clear and distinct and what is false and uncertain. Once we arrive at that point, the whole world of knowledge will open up to us.
Meditation V is an intermediary step in figuring out whether the material world exists. First, Descartes has to figure out whether he can believe even in things about which he has had clear and distinct perception. Naturally, he turns first to geometric and mathematical problems. Descartes, in the rationalist manner, argues that we learn the essence of things not through our interaction with them on a physical level but through our intellect. A triangle is a triangle because it has three sides, not because our senses tell us that a triangle has three sides. Because they are concepts and they exist in our intellect, we can be sure that triangles exist and have three sides. For Descartes, this is a “clear and distinct perception.” Essences of things are always clearly and distinctly perceived.
Turning to the physical world, Descartes asserts we can clearly and distinctly perceive that bodies are “extended.” Extended is a word that Descartes uses to describe something like “has physical mass” or “takes up space.” Therefore, if we so clearly perceive that bodies are extended, then extension must be an essential part of bodies. Part of their essence is to exist in the physical realm. His acceptance of the existence of the body and the physical world in meditation VI is similarly predicated on clear and distinct perceptions of them, ultimately provided by God.
We may find it strange that one of the greatest works of a genius who founded a revolutionary school of philosophy would conclude by agreeing that, yes, we do have bodies after all, but for Descartes, what matters is not the conclusion we reach but the method by which we reach it. His conclusion is the hard-won result of years of study. Obviously, Descartes’ years of study were not undertaken to prove that we have bodies and that the world exists. He never seriously doubted either of these things. His study was undertaken to prove that some form of truth existed and that it was possible to find it. He concludes with the truth that it is permissible to trust that our senses convey accurate information to our brains as long as we apply our intellect to all that information and rightly deduce information from it. And on this simple maxim, a whole new kind of thinking was born.