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 his Meditations 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 the Meditations. 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.
The Meditations 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.