The First Meditation, subtitled "What can be called into doubt," opens with the Meditator reflecting on the number of falsehoods he has believed during his life and on the subsequent faultiness of the body of knowledge he has built up from these falsehoods. He has resolved to sweep away all he thinks he knows and to start again from the foundations, building up his knowledge once more on more certain grounds. He has seated himself alone, by the fire, free of all worries so that he can demolish his former opinions with care.

The Meditator reasons that he need only find some reason to doubt his present opinions in order to prompt him to seek sturdier foundations for his knowledge. Rather than doubt every one of his opinions individually, he reasons that he might cast them all into doubt if he can doubt the foundations and basic principles upon which his opinions are founded.

Everything that the Meditator has accepted as most true he has come to learn from or through his senses. He acknowledges that sometimes the senses can deceive, but only with respect to objects that are very small or far away, and that our sensory knowledge on the whole is quite sturdy. The Meditator acknowledges that insane people might be more deceived, but that he is clearly not one of them and needn't worry himself about that.

However, the Meditator realizes that he is often convinced when he is dreaming that he is sensing real objects. He feels certain that he is awake and sitting by the fire, but reflects that often he has dreamed this very sort of thing and been wholly convinced by it. Though his present sensations may be dream images, he suggests that even dream images are drawn from waking experience, much like paintings in that respect. Even when a painter creates an imaginary creature, like a mermaid, the composite parts are drawn from real things—women and fish, in the case of a mermaid. And even when a painter creates something entirely new, at least the colors in the painting are drawn from real experience. Thus, the Meditator concludes, though he can doubt composite things, he cannot doubt the simple and universal parts from which they are constructed like shape, quantity, size, time, etc. While we can doubt studies based on composite things, like medicine, astronomy, or physics, he concludes that we cannot doubt studies based on simple things, like arithmetic and geometry.

On further reflection, the Meditator realizes that even simple things can be doubted. Omnipotent God could make even our conception of mathematics false. One might argue that God is supremely good and would not lead him to believe falsely all these things. But by this reasoning we should think that God would not deceive him with regard to anything, and yet this is clearly not true. If we suppose there is no God, then there is even greater likelihood of being deceived, since our imperfect senses would not have been created by a perfect being.

The Meditator finds it almost impossible to keep his habitual opinions and assumptions out of his head, try as he might. He resolves to pretend that these opinions are totally false and imaginary in order to counter-balance his habitual way of thinking. He supposes that not God, but some evil demon has committed itself to deceiving him so that everything he thinks he knows is false. By doubting everything, he can at least be sure not to be misled into falsehood by this demon.


The First Meditation is usually approached in one of two ways. First, it can be read as setting the groundwork for the meditations that follow, where doubt is employed as a powerful tool against Aristotelian philosophy. Second, it can, and often is, read standing on its own as the foundation of modern skepticism. We will briefly discuss these complementary readings in turn.

Descartes saw Meditations on First Philosophy as providing the metaphysical underpinning of his new physics. Like Galileo, he sought to overturn two-thousand-year-old prejudices injected into the Western tradition by Aristotle. The Aristotelian thought of Descartes' day placed a great weight on the testimony of the senses, suggesting that all knowledge comes from the senses. The Meditator's suggestion that all one's most certain knowledge comes from the senses is meant to appeal directly to the Aristotelian philosophers who will be reading Meditations on First Philosophy. The motivation, then, behind the First Meditation is to start in a position the Aristotelian philosophers would agree with and then, subtly, to seduce them away from it. Descartes is aware of how revolutionary his ideas are, and must pay lip service to the orthodox opinions of the day in order to be heeded.

Reading the First Meditation as an effort to coax Aristotelians away from their customary opinions allows us to read different interpretations into the different stages of doubt. For instance, there is some debate as to whether Descartes intended his famous "Dream Argument" to suggest the universal possibility of dreaming—that though there is waking experience, I can never know which moments are dreams and which are waking—or the possibility of a universal dream—that my whole life is a dream and that there is no waking world.

If we read Descartes as suggesting the universal possibility of dreaming, we can explain an important distinction between the Dream Argument and the later "Evil Demon Argument." The latter suggests that all we know is false and that we cannot trust the senses one bit. The Dream Argument, if meant to suggest the universal possibility of dreaming, suggests only that the senses are not always and wholly reliable. The Dream Argument questions Aristotelian epistemology, while the Evil Demon Argument does away with it altogether. The "Painter's Analogy," which draws on the Dream Argument, concludes that mathematics and other purely cerebral studies are far more certain than astronomy or physics, which is an important step away from the Aristotelian reliance on the senses and toward Cartesian rationalism.

Meditations on First Philosophy can be seen to follow the model of St. Ignatius of Loyola's Spiritual Exercises. The first step in the Jesuit exercises is to purge oneself of one's attachment to the material, sinful world. In the First Meditation, Descartes leads us through a similar purgation, though with a different purpose. Here he wants to persuade his Aristotelian readers to purge themselves of their prejudices. He also hopes to lead the mind away from the senses that are so heavily relied upon by the Aristotelians. In the meditations that follow, he will argue that our most certain knowledge comes from the mind unaided by the senses. Lastly, this process of radical doubt will hopefully rule out any doubts from the positive claims Descartes will build up in the next five meditations. Read in the wider context of the Meditations, these skeptical doubts are a means to the end of preparing a resistant audience to the metaphysics Descartes plans to build.

Read on its own, the First Meditation can be seen as presenting skeptical doubts as a subject of study in their own right. Certainly, skepticism is a much discussed and hotly debated topic in philosophy, even today. Descartes was the first to raise the mystifying question of how we can claim to know with certainty anything about the world around us. The idea is not that these doubts are probable, but that their possibility can never be entirely ruled out. And if we can never be certain, how can we claim to know anything? Skepticism cuts straight to the heart of the Western philosophical enterprise and its attempt to provide a certain foundation for our knowledge and understanding of the world. It can even be pushed so far as to be read as a challenge to our very notion of rationality.

No one actually lives skepticism—no one actually doubts whether other people really exist—but it is very difficult to justify a dismissal of skepticism. Western philosophy since Descartes has been largely marked and motivated by an effort to overcome this problem. Particularly interesting responses can be found in Hume, Kant, and Wittgenstein.

We should note that Descartes's doubt is a methodological and rational doubt. That is, the Meditator is not just doubting everything at random, but is providing solid reasons for his doubt at each stage. For instance, he rejects the possibility that he might be mad, since that would undercut the rationality that motivates his doubt. Descartes is trying to set up this doubt within a rational framework, and needs to maintain a claim to rationality for his arguments to proceed.

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