To the French philosopher René Descartes, the act of doubting seemed clearly to mark the proper starting point for all philosophical inquiries. The methodology that flows from this approach, many of Descartes’s successors have insisted, laid the foundations of modern philosophy. The beginning of Discourse on Method is a systematic tearing down of learning and education; understanding does not rest, Descartes implies, on received information.
Although usually identified simply as the Discourse on Method, the full title Descartes gave to his brief, five-part essay more accurately reveals the nature of his subject. The full title is Discours de la méthode pour bien conduire sa raison & chercher la vérité dans les sciences (Discourse on the Method of Rightly Conducting the Reason and Seeking for Truth in the Sciences). The Discourse on Method appeared along with three other essays that augment Descartes’s fundamental propositions with details. They were all incorporated in his Philosophical Essays. Descartes believed that all people possess good sense and the unique ability to reason, so the Discourse on Method was written in French in an era when Latin was the language of Europe’s academic, intellectual, and religious elites. It was Descartes’s intention to reach a relatively large audience.
Descartes completed this essay well before 1637. When he was twenty-three, in fact, he recorded a series of dreams that inspired him to establish a new philosophical and scientific system. Moreover, his basic ideas and methodology were shared among his friends and correspondents for years before the book was published. Several things had dissuaded him from publishing. He was aware, first of all, of Galileo Galilei’s condemnation by the Catholic Church for having defended the theory of Nicolaus Copernicus (published in 1512) that Earth and the other planets revolved about the Sun. Rigorously trained by Jesuits at La Flèche College and a sincere Catholic, Descartes accordingly suppressed his own cosmological ideas until he had gotten them to conform to those of his church. He also deeply valued time for meditation, thought, and reflection: time, that is, for leisure. Consequently, to publish his views was to invite the time-consuming bothers caused by approving adherents and by angry critics alike. Furthermore, since to his own satisfaction he had largely resolved many of the intellectual problems he examined, he lacked incentive to publish. The urgings of friends, a sense of social obligation, and some vanity persuaded him, at the then-advanced age of forty-one, finally to publish.
In the Discourse on Method Descartes approached the ancient philosophical questions of What is true? and What is certain? He employed a novel method. He styled his exposition modestly. He was not interested, he wrote, in pedantically laying down precepts for others to follow. They, after all, would respond to the dictates of their own reason. He was concerned also about the possibility of being in error, so much so that he offered his “Tract . . . merely as a history, or . . . as a tale” that might yield examples worthy of emulation. Read in this light, the Discourse on Method recounts the steps of his intellectual adventure, the progress made en route, and the conclusions drawn when he reached his destination.
To launch himself anew Descartes describes how, figuratively, he divested himself of intellectual baggage and of prejudices acquired from his worldly experience. As one born of a seminoble class, for instance, he had engaged in the diversions of aristocrats, had served with the armies of Maurice of Nassau and Johann Tzerclaes, Count Tilly, during his early twenties, and had spent several years in Paris studying science, prior...
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to embarking upon two decades of solitude and immersion in his work in Holland, later in Sweden. The experiences and the conventional authorities that once had nourished his mind had ceased to sustain him. The insights and methods of languages, history, theology, morals, ethics, eloquence, poetry, jurisprudence, medicine, and scholastic philosophy—in each of which he was well versed—he discarded as too obscure and too imprecise to afford him a pathway to truth and certainty.
What Descartes sought to discover was a body of self-evident truth. He sought certainties that, with the common endowments of good sense, humanity could accept. Descartes also wrote the Discourse on Method with another purpose in mind. What he sought to effect, in addition, was the reconciliation of the mechanical explanation of everything in nature (the assumptions of the new science of his day) with the cherished spiritual doctrines and values of Christianity.
Descartes chose mathematics as the exemplar of the precise and logical reasoning that could be applied to the resolution of philosophical problems. The rigorous rules and axioms of mathematics, it seemed evident to him, showed the way to certainties. Certain it was and always would be, for example, that three and three were six. A young child and a mathematical genius eternally arrive at the same result. Descartes had a profound interest in mathematics, and he made an indelible impact on its advancement. He has been recognized universally for his seminal contributions to algebra and, among other achievements, he is generally credited with founding analytical geometry. Important mathematical concepts continue to bear his name.
It was as a mathematician, then, that Descartes turned to rectifying philosophy, doubting everything, and reducing everything to what he alone, not authority, could establish as certain. Such reductionism established a single fact: Doubt itself could not be doubted. For, logically, to doubt was to think, and to think was to exist. From this reasoning comes the famous affirmation: Cogito, ergo sum (I think, therefore I am). This Descartes described as “the first and most certain knowledge that occurs to one who philosophizes in an orderly manner.” Acknowledging his famous phrase to be a clear and self-evident axiom, a test of truth that provides a distinctly perceived certainty, Descartes proposed as a general rule that everything clearly perceived as its corollary is true.
Having found a starting point of self-evident truth, the next step for Descartes was to resolve another problem: What if there were no God, or if there were, what if God were a deceiver who surrounds people with illusions? To unravel these questions, he began by positing his idea that God, the Creator of all things, a perfect, infinite being, preexisted within him. The idea of God had to be innate. Nothing comes from nothing, and since there is something, God exists. Descartes had not created himself and thereby was imperfect and mortal. The conception of God had to have been received from a perfect, omnipotent, omniscient, and infinite being, therefore making it manifest that God exists. Descartes’s knowledge of God implied the existence of a being greater than Descartes himself.
With God established as a certainty, Descartes then deals with the ancient philosophical problem of body and mind. It was essential for Descartes to reconcile the new science, to which he was devoted, to his religion, which claimed an equal measure of his devotion. Mounting evidence from science, most of it based upon mathematical inquiries and solutions, demonstrated that the entire physical world could be explained in mechanical terms (with God as the prime mover of the universe). God designed these mechanics, setting the physical bodies of the universe in motion in unalterable conformity with unchanging laws. For Descartes, natural laws were laws of motion, and differences between physical bodies were explicable as differences between their various parts. Having created the world as chaos, God, according to Descartes, thereafter enabled it “to act as it is wont to do”: evolve in obedience to those laws.
Using medical analogies, Descartes assigned human functions to the realm of nature; they operate in accordance with its mechanical laws. He declared, however, that humanity’s rational and spiritual qualities were entirely separate from bodily functions and could not be “educed from the power of nature.” Humanity’s “Reasonable Soul,” that is, its rational and spiritual attributes, had been created by God. Occasionally, mind and body interact, which accounts for human comprehension of sensations and appetites. Descartes’s notion of such “occasionalism” still left mind and body substantially separate. The mechanical and passive body that operates in accord with the laws of nature eventually dies, but the soul continues on as immortal.
The Discourse on Method is a master sketch. Descartes deploys the details of his theory of mathematical methodology and ways to discover scientific truth in the three essays printed along with the Discourse on Method as well as in his Meditationes de prima philosophia (1641; Meditations on First Philosophy, 1680) and his Principia philosophiae (1644; Principles of Philosophy, 1983). Collectively, neither these nor other of Descartes’s writings represent a systematic theory of knowledge. His interests were never pointed in that direction. Rather, the Discourse on Method and his other essays expound a method of identifying truth or self-evident certainties. Alone, one’s sensory experiences, he believed, can never yield either self-evident truths or certainties. Certainties result from individuals’ reasoning deductively from basic principles that were inherent in the mind. Such principles are innate, fixing in the mind the standards that guide it to truth.
The Discourse on Method, however, leaves unexplained how innate ideas enter the mind in the first place, though the implication is that God places them there. Descartes also remains vague about how one’s faculty of reason comes to possess natural canons for assessing truth. The meaning imparted to innate ideas is likewise confused. Sometimes Descartes implies that innate ideas impress themselves on the mind. Sometimes, he calls innate ideas principles discovered in the soul. Elsewhere he suggests the soul has the power to generate the knowledge from experience. He is unclear, too, about how, if God is pure spirit, he could lay down the rules governing a mechanical universe or could impart motion to matter.
Critics swiftly pointed to the deficiencies of Descartes’s rationalism and use of a priori reasoning. They readily comprehended that his errors stem from his attempts at reconciling a mechanistic science with Catholic theology. Before long, philosophers Gottfried Leibniz, Immanuel Kant, Nicolas Malebranche, Pierre Bayle, Baruch Spinoza, and Thomas Hobbes, among others, tried rectifying, or avoiding, Descartes’s difficulties. Other philosophers such as John Locke simply rejected Descartes’s entire concept of innate ideas, or the way he separated the material and the spiritual. For their part, Jesuits denounced the message of the Discourse on Method and officially banned it in 1663. Dutch Calvinists likewise opposed it, and many French and German universities prohibited students from reading it.
The Discourse on Method nevertheless won Descartes an international reputation. Cartesian philosophy soon garnered a host of disciples, drew attention to vital questions, and expounded the philosophical values of an orderly, logical mathematical method.