René Descartes Dreams the “Philosopher’s Dream”—And Launches Modern Philosophy

In winter 1619, the man who became the “founder of modern philosophy,” the first great philosophical challenge to centuries of Christianized Aristotelian Scholasticism, found himself caught by winter in the little town of Ulm, near Munich. René Descartes (1596–1650) had been returning to the Catholic army of the Duke of Bavaria, recently crowned emperor of the Holy Roman Empire.

There, in a little cottage with a wood-burning stove, on the night of November 10, Descartes had three dreams that he took as defining his mission in life. All reports are that the dreams are not an apocryphal incident fashioned or elaborated by historians. Descartes really dreamed and described his dreams at some length.

Descartes already had become familiar with the history of philosophy and contemporary philosophers and had achieved success in mathematics and natural science. In fact, what he dreamed could be called the timeless “philosopher’s dream.” He envisioned, as had philosophers since Plato, that he must reform all knowledge, know the true nature of existence, man’s place in it, and, above all, how one could be certain of this knowledge. (One of Descartes’s goals, even then, was to root his work in physics and other natural sciences in a true ontology (philosophy of the nature of being).

More remarkable than the dreams, by common agreement of historians and philosophers, was that Descartes went on to develop this new philosophy and change the thinking of every educated European—and educated persons within the orbit of European thought. His philosophy, during the seventeenth century, became the reigning alternative to the Christian Scholasticism that dominated universities across Europe—so much so that arriving students were given a handbook of Christianized Aristotelian dogmas and told that their thinking and reading must not depart from these. That was true, for example, when Adam Smith and John Locke—among many others—arrived at the University of Oxford. 

Born in 1596 in La Haye, France, in the Loire Valley, with a mostly absent lawyer father, Descartes lost his mother before he was one-and-a-half, and so lived with his grandmother and later with his great uncle, a lawyer in the service of the king of Châtellerault. Whether out of vanity or impishness, or both, Descartes later introduced himself as Lord of Perron, after a small farm he had inherited in Poitou; and, referring to the region of his birth, he said he was “a man who was born in the gardens of Touraine.” (Later, La Haye changed its name to “Descartes.”)

Descartes’s 1596 birthdate positions him at the starting line of the seventeenth-century Age of Science and a century before the onset of the eighteenth-century Age of Enlightenment. The only notable “Enlightenment” figure who predates him is the Englishman Francis Bacon (1561–1626), who strove, in the name of empiricism, to disentangle science from religion. 

Beginning at age eight (old for those days because his early life was disrupted by fragile health), Descartes entered the Jesuit College (in France a “middle school”) Henri IV at La Flèche, boarding and studying for seven or eight years. Of course, by rule, the Jesuit philosophy curriculum followed Aristotle, divided into the standard topics of logic, morals, physics, and metaphysics. But the Jesuits included mathematics in the last three years of study and it must have taken hold. Descartes became one of the great mathematicians of his time. To take a single example, he discovered the fundamental principles that make analytical geometry possible. (What we now call “Cartesian coordinates” are named in his honor.) Fortunately, study of Aristotle was supplemented by investigation of the ancient atomists, Plato, the Stoics, and the skeptics—as well as the literature of Cicero. All of it shaped Descartes’s later work—as did landmark events known at La Flèche such as Galileo’s discovery in 1610 of the moons of Jupiter. Thus, Scholastic Aristotelianism did not dominate philosophy to the exclusion of other (though not fundamentally different) views.

Later, in 1637, Descartes would write in his Discourse on the Method, in a section of autobiography, that leaving school “I found myself beset by so many doubts and errors that I came to think I had gained nothing from my attempts to become educated but increasing recognition of my ignorance.” (For all that, he praises—sometimes extravagantly—La Flèche and its diverse curriculum.) Naturally, he said, the philosophy had to be uncertain; was he not in the Discourse offering the first introduction to the one true philosophy, which he himself had discovered?

His college education complete, the question arose of what he would do for a living. The many lawyers in his extended family were unanimous that it must be law. Descartes bowed to their wishes, attending law school and obtaining a degree. He never practiced law. The consummate “intellectual in the making” elected to become a mercenary in the forces of Protestant Prince Maurice in his civil war with the Catholic part of the Netherlands. To do so, he moved to Breda, near Amsterdam, where he met the man who set him on his course to become both a famous mathematician and natural philosopher (scientist). Isaac Beeckman, a Dutch mathematician and natural philosopher, worked with Descartes on what they came to call mathematical-physics. Here, perhaps, Descartes’s training in ancient philosophy came into play. He and Beeckman proceeded on the premise of atomism. They hypothesized that they should look to atoms as the basic constituents of matter—with size, shape, and motion—for the explanation of phenomena. Motion was explainable by the laws of mechanics, “making possible a rigorous new quantitative science of all physical reality.” This was a radical departure from Scholasticism, with its explanations by reference to Aristotle’s four types of causality, including “final cause”—the “to what end” things acted.

Descartes’s atomistic view, as taken up by scientists in the seventeenth century and philosophers in the eighteenth century, is fundamental to thought today. Our world of matter, with a few fundamental and universal laws, is composed of atoms; ultimately, interactions among all entities can be explained at this level. Putting the idea perhaps too briefly, he said: “But in my opinion, all things in nature occur mathematically.” 

Today, that includes the virtually universal position of neuroscientists that our material brain, in the natural world, explains the existence and action of our mind. It was Descartes who handed down to us the modern view that the mind, although an immaterial substance, is directly related to the brain—the latter’s origin and nature not to be fancied part of another world of heavenly and subheavenly spirits. The problem he bequeathed to us: How do the immaterial mind and material brain governed by natural mechanisms, two different substances, interact—as obviously they do in the human body? Descartes did not claim to have an answer.

Descartes derived his method for attaining certain knowledge from mathematics but also from a thread recovered from ancient philosophy during the sixteenth century: skepticism. It was a prominent theme that alarmed Scholastic academics, for students love to subject the ideas of their professors to radical questioning. Descartes also used skepticism, including the most extreme (called “hyperbolic doubt”), as a methodological tool. Thus, mathematics (especially geometry) sets the basic methodology: identify basic premises and deduce from them, by logic, all other principles. This came to be called “rationalism,” one of the two great epistemological methods (the other being empiricism). But how to arrive at those “basic premises” at the foundation of thinking? To deduce them from other premises leads to infinite regress. But if basic premises cannot be established as certain, then deduction from them—all knowledge—cannot be certain. That defeats the “philosopher’s dream.”

Descartes sought his basic premises by the method of radical doubt. As he succinctly put it: “In order to seek truth, it is necessary once in the course of our life to doubt, as far as possible, of all things.” What could not be doubted? He posed many possibilities before he arrived at his answer—among the most famous formulations in philosophy: “cogito ergo sum,” Latin for “I think, therefore I am.” I can doubt everything else, but I cannot doubt that I—the entity that is doubting—exist. For Descartes, this passed the test of an idea perfectly clear and definite. From his footing on this epistemological rock, Descartes made certain other deductive leaps. Every clear and distinct idea in our mind has a cause. Therefore, God exists because we have the idea of an infinitely perfect being and a necessary property of such perfection is existence.

To elaborate on this point: “The cogito is a logically self-evident truth that also gives intuitively certain knowledge of a particular thing’s existence—that is, one’s self. Nevertheless, it justifies accepting as certain only the existence of the person who thinks it. If all one ever knew for certain was that one exists, and if one adhered to Descartes’s method of doubting all that is uncertain, then one would be reduced to solipsism, the view that nothing exists but one’s self and thoughts. To escape solipsism, Descartes argues that all ideas that are as ‘clear and distinct’ as the cogito must be true, for, if they were not, the cogito also, as a member of the class of clear and distinct ideas, could be doubted. Since ‘I think, I am’ cannot be doubted, all clear and distinct ideas must be true.”

This resolved Descartes’s fiercest radical skeptical challenge: What if there exists a malevolent being, a “supreme evil genius,” whose purpose is to deceive us? To make the false seem certain? But a perfect God would not permit such a being to exist.

Likewise, Descartes had a clear and distinct idea of an external world; a perfect God would not permit us to be deceived about this. Our undoubtable idea about the external, material world is that it has extension—occupies space. Our undoubtable idea about the soul is that its essence is thought (for example, doubts) as already established. And so, it is certain that we exist in a real, material world, that we think, and that a perfect being, whom we call God, with supreme benevolence, created this world. 

It is his argument for God’s existence that epitomizes the nature of rationalism. The ontological argument itself was introduced by the medieval English logician St. Anselm of Canterbury (1033/34–1109). It establishes certain knowledge about an existing thing solely on the basis of reasoning from innate ideas, with no help from sensory experience. This rationalist logic, admittedly reduced here to a bare-bones summary, was enormously convincing to readers of Descartes’s eloquent expositions of philosophy: Discourse on the Method (in French, 1637), Meditations on the First Philosophy (in Latin, 1641), Principles of Philosophy (in Latin, 1644), and Passions of the Soul (in French, 1649), the latter about emotions.

But Descartes’s rationalist logic, even as laid out at length in these works, probably strikes most modern readers as quaint cerebral acrobatics. Accustomed to arguments in philosophy and science that establish their basic premises by reference to observation, Descartes may seem almost to be playing a mental chess game. Emphatically, he did not appear thus to his contemporaries. His rejection of any reference to “authority” or a philosophical tradition, his rejection of any appeal to the religious canon, his radical departure from Christianized Aristotelianism, and his insistence that his was an exploration of the foundations of science swept Europe even in Descartes’s lifetime. Scholasticism at last had a potent rival for the minds of university students, their professors, and later philosophers such as Benedict Spinoza and Wilhelm Leibniz, both rationalists, both giants in philosophical history. These rivals of Scholasticism were called “Cartesians,” derived from the Latin name under which Descartes published his works.

University of Pennsylvania professor Alan Kors writes in The Birth of the Modern Mind: The Intellectual History of the 17th and 18th Centuries that Descartes “created on the Continent the major challenge to the scholastic hegemony. . . . For legions of disciplines, it freed philosophy from authority and . . . [Christianized] Aristotelianism.” Descartes “demonstrated that we could establish a criterion of truth . . . certainty about the real nature and the real causes of things.”

Professor Anthony Paglen, in The Enlightenment and Why It Still Matters, suggests the likely impact on religion: “Not many skeptics went so far as to doubt the existence of the world. But Descartes’s point is much the same as both [Michel de] Montaigne’s and John Donne’s: The only things of which I can be certain must come directly from the individual in his or her immediate and direct contact with the external world. The implications for the traditional Christian view of the world of even a moderate form of this kind of skeptical reasoning could be devastating.”

Once Descaretes moved to the Dutch Netherlands, in 1628, he seldom returned to France. It was a flight to the country of the greatest toleration then available in Europe—very much in contrast with France. He was sensitive to the furious reaction of the churchmen to his challenge to Scholasticism—indeed, he had sought out their views to include in the second edition of his Discourse. In the Netherlands, he had kept his address secret, changing his living quarters eighteen times, saying: “Who lives well hidden, lives well.” Along the way (1635) he had a daughter, Francine, with his housekeeper. Francine died of scarlet fever when she was five, said to be the greatest sorrow of Descartes’s life. Descartes had not married the mother and now gave her part of a dowry for her marriage.

Having established his metaphysics, Descartes felt it time to publish his work on physics, which was taught across much of Europe. In Catholic countries, however, teaching of his philosophy was suppressed when his works were added to the Index of Prohibited Books in 1663 (thirteen years after Descartes’s death). In the Netherlands, he fell afoul of Calvinism, and the rector of the University of Utrecht won a vote of the faculty senate to condemn Descartes’s philosophy.

Typically of leading Enlightenment men, Descartes won the attention of a monarch captivated by new ideas of science and philosophy. In 1649, he accepted (it is said, reluctantly) Queen Christina’s invitation to join her court in Sweden. He may have been seeking patronage and also escaping menacing Calvinists in the Netherlands. Descartes took on the assignment of composing the statutes of the Swedish Royal Academy. It was his last achievement. He became ill on the very day he delivered them to the queen and never recovered. He died of pneumonia in Stockholm in February 1650. Many pious final words are attributed to him, perhaps by those who would appease religionists, but the only first-hand account is from his German butler, who reported that Descartes said nothing.