A Life in Ideas: René Descartes

By Neel Burton | July 25, 2026

His Life, Character, and Philosophy

Descartes by the cocklestove — Modern philosophy began in the warmth of a cockle stove, with three visions.

By Dr Neel Burton — Psychiatrist, philosopher, and wine writer; Fellow of Green Templeton College, University of Oxford; author of over twenty books.

René Descartes (1596–1650) is often called the father of modern philosophy. The title owes less to any single doctrine than to the ambition of his project. As the old Aristotelian worldview collapsed under the weight of the Scientific Revolution, Descartes set out to rebuild human knowledge from the ground up, in a way that could accommodate God, the soul, and human freedom.

A World Crying Out For a Philosopher

The demise of the Aristotelian system, brought about by the Copernican and Scientific Revolutions, left a void that needed filling—ideally by some all-encompassing metaphysical system on the scale of the old, Aristotelian one. If the Earth no longer stood at the centre of the cosmos, was man not the glory of creation, as affirmed in the Bible (1 Corinthians 11:7)? In this new mechanistic, atomistic world of matter in motion, where might God and the immaterial soul fit in? Where freedom and justice? And where, even, heaven and hell?

As recently as 1588, Galileo, qua mathematician, had been invited to address the Florentine Academy on the location, size, and arrangement of hell as described in Dante’s Inferno—underscoring the scale of the mind shift required. Even that paragon of the Scientific Revolution, Newton, albeit in secret, dedicated the larger part of his life to alchemy and the search for the fabled philosopher’s stone.

The three seventeenth-century philosophers who rose to the challenge of formulating a comprehensive metaphysics are René Descartes (1596–1650), Baruch Spinoza (1632–1677), and Gottfried Wilhelm Leibniz (1646–1716), who sometimes inserted, with little to no justification, the nobiliary particle von in front of his cognomen.

Three Visions in a Stove-Heated Room

Descartes categorically rejected the substantial forms and primary matter of the mediaeval, Aristotelian schoolmen. In a letter to his friend Marin Mersenne dated 28 January 1641, he writes that his Meditations on First Philosophy ‘contain all the foundations of my physics. But please do not tell people, for that might make it harder for the supporters of Aristotle to approve them. I hope that readers will gradually get used to my principles, and recognise their truth, before they notice that they destroy the principles of Aristotle.’

Two decades earlier, Descartes had been serving in the army of Duke Maximilian of Bavaria. On 10–11 November 1619, while stationed near Ulm or else Neuberg an der Donau, he found refuge in a room with an ‘oven’ (probably a cockle stove) to escape from the cold and reflect on his thoughts. That night, he had three dreams which determined the course of his life. To repay these visions, he vowed to make a pilgrimage to the shrine of Our Lady of Loretto in the Italian region of Marche—and, in 1623, fulfilled his vow.

What Descartes had seen or grasped on that eve of St Martin’s Day 1619 is the unity of the sciences under mathematics: if a concrete problem could be abstracted into mathematical form, it would become clearer and more amenable to solving. Thus, in the course of his life, he contributed several mathematical innovations. In his La Géométrie (1637), he introduced the modern exponential notation which is taught in every contemporary school. He established the convention of using the letters x, y, z to represent unknown variables in equations, and a, b, c to represent known variables. If that were not impressive enough, he bridged algebra and geometry by transforming numerical relationships into geometrical shapes, plotting these lines and curves on a coordinate plane, and showing how they could be represented in the form of algebraic equations—a field now known as analytic, coordinate, or Cartesian geometry.

Descartes sought to carry the certainty of mathematics into philosophy itself. The culmination of that lifelong project was the Meditations on First Philosophy, which laid the foundations of his new metaphysical system while quietly dismantling that of Aristotle.

The Method of Doubt (Dubitatio methodica)

The closed-in stove-heated room later came to symbolise Descartes’ famous method of doubt, by which he systematically dismantled the edifice of his beliefs to rebuild on a more secure foundation of indubitable truths, to be arrived at through a predetermined set of logical rules.

In this climate of radical doubt, he could doubt the existence of the outside world, even the existence of his own body—but not that he was the one doing the doubting. This insight is encapsulated in his famous dictum, Cogito, ergo sum (‘I think, therefore I am’). The very act of doubting presupposed a thinking self to do the doubting.

Although Descartes knew that he was thinking, and so that he was, he could not be sure that his thinking bore any relation to the outside world. So he introduced an a priori proof (a proof derived from thought alone) for the existence of God, and argued that such a benevolent being would not deceive his favoured creation, man—so long as man had employed his (Descartes’s) method of doubt and taken every precaution to have ‘clear and distinct’ ideas and not to be deceived.

Dualism and the Piece of Wax Analogy

The Cogito also transformed Descartes’ understanding of reality. The indubitability of the thinking self led him to conclude that mind and body must be fundamentally different kinds of substance. The defining attribute of the mind (or soul, or res cogitans) is thought, while that of the body (or res extensa) is extension. It is by the knowable mind, rather than the deceptive senses, that the physical can be apprehended.

Descartes illustrated this point with one of the most famous passages in the Meditations: the wax analogy. When a piece of wax is heated, all its sensory properties change. Only the mind grasps its underlying essence, which consists in extension (as well as flexibility and movability in space), and recognises it as the same piece of wax. The physical, being extended, is divisible; but mind is indivisible, and therefore not physical. Since it is not physical, mind is beyond the laws of physics, and free and immortal.

[T]here is a great difference between the mind and the body, inasmuch as the body is by its very nature always divisible, while the mind is utterly indivisible. For when I consider the mind, or myself in so far as I am merely a thinking thing, I am unable to distinguish any parts within myself; I understand myself to be something quite single and complete… By contrast, there is no corporeal or extended thing that I can think of which in my thought I cannot easily divide into parts; and this very fact makes me understand that it is divisible. This one argument would be enough to show me that the mind is completely different from the body.

The Soul of Animals

Descartes’s mind-body dualism is commonly taken as the starting point of modern philosophy. His method is indeed revolutionary, but the substance of his philosophy is in fact an attempt to shelter God, man, and his immortal soul from the new mechanism. Thanks to Descartes, those who embraced the Copernican revolution could remain good Christians, or claim as much.

But in solving one problem, Descartes created several others, most notably the place of animals and the mind-body problem.

Under the Aristotelian system, all living things had a vegetative (or nutritive) soul; animals, in addition, had a sensitive soul; and humans, on top of that, had a rational soul.

For fear of granting them immortality and a place in heaven, Descartes denied souls to the animals. Animals, he claimed, are mere automata, whose functions ‘follow from the mere arrangement of the machine’s organs every bit as naturally as the movements of a clock or other automaton follow from the arrangement of its counterweights and wheels’.

For Descartes, it is not merely that animals do not reason, but also, contra common sense, that they do not feel, perceive, or sense. Clearly, he did not have a cat. According to lore, he once threw a cat out of a window in an attempt to demonstrate that the poor thing lacked consciousness.

The Mind-Body Problem

If mind and body truly are incommensurate, how is it possible for them to interact? How might my mind move me to write these words without violating, or else submitting to, the laws of physics? Conversely, how might my eyes and ears relay sense experience to my mind?

Descartes responded to this so-called mind-body problem in two ways. At times, he said, literally, ‘Only God knows.’ At other times, he suggested that mind and body interact at the pineal gland, on the grounds that this structure is mobile and central in the brain. But this only puts the problem at one remove, for the question then becomes, how is it possible for the mind to interact with the pineal gland?

The Philosopher’s Daughter

Although France’s most famous philosopher, Descartes spent the greater part of his adult life in the relative safety of the Dutch Republic. There, he met a servant called Helena who became the mother of his illegitimate daughter Francine (b. 1635), whom he passed off as his niece. When Francine died, aged five, of scarlet fever, he called it the greatest sorrow of his life, even stating that it was not unmanly to cry. Later, a legend arose that he—the philosopher who had compared living bodies to machines—constructed an automaton in her likeness.

The Tree of Life

The name René derives from the Latin Renatus, ‘born again’—fitting for the man who sought to rebuild philosophy from first principles. But although remembered as a philosopher, Descartes looked upon himself first and foremost as a natural philosopher (scientist) and physicist.

In the preface to his Principles of Philosophy (1644), he compared philosophy to a tree, with metaphysics as its roots, physics as its trunk, and the other sciences as its branches—and it is, of course, the branches that bear the fruit.

The ‘other sciences’ could be reduced to three principal ones, medicine, mechanics, and morals—which is why, in 1649, he published a book on the emotions, The Passions of the Soul. He sent a copy to his penfriend Queen Christina of Sweden, who was so impressed that she invited him to join her court.

In October 1649, he left Holland for Sweden. But the northern winter did not agree with him, and the frenetic Christina insisted on taking her lessons at five in the morning. He did not live to see the spring.

Continue Exploring

If you enjoyed this article, you might also enjoy The German Greeks, which traces the development of modern philosophy from Descartes to Nietzsche, via Leibniz, Kant, Hegel, and Schopenhauer.

You may also enjoy

God Is Dead. Now What?

By Neel Burton | May 23, 2026

How Would You Respond to Nietzsche’s Madman?

By Dr Neel Burton — Psychiatrist, philosopher, and wine writer; Fellow of Green Templeton College, University of Oxford; author of over twenty books.

Essay substantially revised on 15 August 2026.

The Scientific Revolution disrupted the centuries-old Aristotelian system of the Church and universities. It all began in 1543, when the Pole Nicolaus Copernicus published On the Revolutions of the Heavenly Spheres. This work challenged the geocentric system of Aristotle and Ptolemy in which the Earth—and, more importantly, man—stood proud and unmoving at the centre of the universe. The Aristotelian system had provided not only a scientific model but also a moral and metaphysical order, with everything in its proper place. To overthrow it was to overthrow everything.

It is arguably Newton who completed the Copernican Revolution, and put the nail in the coffin of the Aristotelian system, with the publication, in 1687, of his Principia mathematica. In this work, which is deemed impenetrable, he introduced his three laws of motion along with the Law of Universal Gravitation. These laws applied to the celestial spheres as much as to a falling apple—with the implication that the heavens were not some separate, higher realm, but of one piece with your backyard.

In the mid-1660s, Newton kept a notebook with the title, Certain Philosophical Questions. Above this title, he inscribed the motto (which is a paraphrase of Aristotle): Plato is my friend, Aristotle is my friend, but truth is a greater friend still.

The More Radical Revolution

Also undermining the Aristotelian worldview were William Harvey’s demonstration of the circulation of blood, published in his De motu cordis of 1628, and Galileo’s discovery that falling objects undergo uniform acceleration irrespective of their mass, published in his Dialogue Concerning the Two Chief World Systems (i.e. the Aristotelian-Ptolemaic and the Copernican) of 1632. Old Aristotle had held that heavier objects fall faster, and that blood is constantly produced in the liver and consumed in the body’s periphery.

More radically, both Harvey and Galileo privileged experiment and observation over the authority of Aristotle, Ptolemy, Galen, and the Bible. Only a decade earlier, in 1620, Francis Bacon had formalised the modern scientific method in his Novum organum, which sought to undermine and replace Aristotle’s canonical treatise on logic, the Organon (hence the title, Novum organum, or New Organon). Galileo even had the gall to publish in Italian rather than the de rigueur Latin.

The revolution was not merely in what people believed, but in how they came to believe it—and who they should believe.

In Search of a Hero

The demise of the Aristotelian system, for all its promises, left a void that needed filling, ideally by some all-encompassing metaphysical system on the scale of the old, Aristotelian one. If the Earth no longer stood at the centre of the cosmos, was man not the glory of creation, as affirmed in the Bible (1 Corinthians 11:7)? In this new mechanistic, atomistic world of matter in motion, where might God and the immaterial soul fit in? Where freedom and justice? And where, therefore, heaven and hell?

Consider the scale of the imaginative shift required. In 1588, as a young mathematician, Galileo had been invited to address the Florentine Academy on the location, size, and arrangement of hell as described in Dante’s Inferno. The Scientific Revolution had begun to dismantle the circles of hell, and everything else, while remaining silent on what might replace them.

The three men who rose to the almost impossible challenge of weaving a new metaphysics that could accommodate the Scientific Revolution and make sense of man’s place within it were René Descartes (1596–1650), Baruch Spinoza (1632–1677), and Gottfried Wilhelm Leibniz (1646–1716).

Each offered a radically different solution. Descartes preserved God and the immortal soul by splitting reality into mind and matter. But in so doing, he created the problem of how such radically different substances might interact. Spinoza went in the opposite direction, collapsing mind and matter by identifying God with Nature. Leibniz sought another way out of the mind-body problem: his universe consisted not of interacting minds and bodies but of immaterial ‘monads’, co-ordinated by God in a ‘pre-established harmony’. Whereas Descartes and Leibniz sought to salvage what they could, and reaffirm man’s position in the order of things, the ‘heretic’ Spinoza provided no such comforts.

In November 1676, Leibniz travelled to The Hague to meet the dying Spinoza. He had been troubled by Spinoza’s still-secret metaphysics, and spent hours in discussion with him. If God and Nature were one and the same, and everything followed necessarily from the nature of God, what became of freedom, providence, and man’s special place in creation? Leibniz’s own metaphysics—the monadology—can be read as an attempt to solve Descartes’s mind-body problem without falling into Spinozism.

Nietzsche’s Break

By Nietzsche’s time, the great metaphysical systems had begun to look like what they were: elaborate attempts to salvage God and the soul of man from the assaults of science.

In The Gay Science (1882), Nietzsche calls time on the projects of his predecessors. Nietzsche could not have been more categorical about this: God, he declares, is dead.

Nietzsche was not simply announcing his atheism. By the late nineteenth century, there would have been nothing new in that. Instead, he was pointing to the consequences of unbelief: if our highest values—human dignity, moral obligation, justice—are founded in God, what happens to them if we can no longer believe in this God? Do we just go around pretending as if nothing had changed? Or do we invent ourselves anew?

The Gay Science is especially remembered for Aphorism 125, the so-called Parable of the Madman. In it, a madman lights a lantern in the bright morning hours, runs into the marketplace, and cries incessantly, ‘I seek God! I seek God!’ When the people laugh and jeer at him, he jumps into their midst and pierces them with his eyes: ‘Whither is God? … I will tell you. We have killed him—you and I. All of us are his murderers. But how did we do this? How could we drink up the seas? Who gave us the sponge to wipe away the entire horizon?’

What were we doing when we unchained this earth from its sun? Whither is it moving now? Whither are we moving? Away from all suns? Are we not plunging continually? Backward, sideward, forward, in all directions? Is there still any up or down? Are we not straying, as through an infinite nothing? Do we not feel the breath of empty space? Has it not become colder? Is not night continually closing in on us? Do we not need to light lanterns in the morning? Do we hear nothing as yet of the din of the gravediggers who are burying God? Do we smell nothing as yet of the divine decomposition? Gods, too, decompose. God is dead. God remains dead. And we have killed him. [Gott ist tot! Gott bleibt tot! Und wir haben ihn getötet!]

Later that same day, the madman forces his way into several churches to strike up a requiem for God. When dragged out and called to account, he always replies, ‘What after all are these churches now if not the tombs and sepulchres of God?’ [Was sind denn diese Kirchen noch, wenn sie nicht die Gräber und Grabmäler Gottes sind?]

The townspeople are not scandalised by the Madman’s atheism. They are themselves unbelievers, which is why they laugh at him. The joke, however, is on them. They have abandoned God without thinking it through. The Madman has arrived, then as today, ‘too early’.

Instead of facing up to this crisis, we linger in a state of denial and false hope, like Beckett’s Vladimir and Estragon, who lend their lives structure and meaning by waiting for Godot.

In response to the death of God, Nietzsche advocates a so-called ‘gay science’: a sceptical, light-hearted, artistic approach to life. Nietzsche’s response to the collapse of certainty is not despair, as is often thought, but freedom, creation, and experimentation: the courage to live without assurances and treat life as something to be interpreted, repurposed, and affirmed.

Not simply hanging around, unsure whether to stay or leave.