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René Descartes
Frans Hals - Portret van René Descartes.jpg
Portrait after Frans Hals
Born 31 March 1596 (1596-03-31)
La Haye en Touraine, Touraine, Kingdom of France (now Descartes, Indre-et-Loire)
Died 11 February 1650 (1650-02-12) (aged 53)
Education
  • Collège Royal Henry-Le-Grand (1607–1614)
  • University of Poitiers (LL.B., 1616)
  • University of Franeker (no degree)
  • Leiden University (no degree)
Era
Region
School
  • Rationalism
  • Cartesianism
  • Mechanism
  • Innatism
  • Foundationalism
  • Conceptualism
  • Augustinianism
  • Indirect realism
  • Correspondence theory of truth
  • Corpuscularianism
  • Theological voluntarism
Thesis Untitled LL.B. thesis (1616)
Main interests
Epistemology, metaphysics, mathematics, physics, cosmology, ethics
Notable ideas
Signature
Firma Descartes.svg

René Descartes ( or Latinized: Renatus Cartesius; 31 March 1596 – 11 February 1650) was a French philosopher, scientist, and mathematician. Descartes spent much of his working life in the Dutch Republic, initially serving the Dutch States Army, later becoming a central intellectual of the Dutch Golden Age.

His best known philosophical statement is "Latin: [cogito, ergo sum] Error: {{Lang}}: text has italic markup (help)" ("I think, therefore I am"; French: Je pense, donc je suis) and "I know that I know something, anyone who knows exists, then I exist" (nosco me aliquid noscere, & quidquid noscit, est, ergo ego sum).

Descartes believed that the brain resembled a working machine and unlike many of his contemporaries, he believed that mathematics and mechanics could explain the most complicated processes of the mind. In the 20th century, Alan Turing advanced computer science based on mathematical biology as inspired by Descartes. His theories on reflexes also served as the foundation for advanced physiological theories, more than 200 years after his death. The physiologist Ivan Pavlov was a great admirer of Descartes.

Descartes has often been called the father of modern philosophy.

Life

Early life

Maison de René DESCARTES - Jean-Charles GUILLO
The house where Descartes was born in La Haye en Touraine

René Descartes was born in La Haye en Touraine, Province of Touraine (now Descartes, Indre-et-Loire), France, on 31 March 1596. In May 1597, his mother Jeanne Brochard, died a few days after giving birth to a still-born child. Descartes' father, Joachim, was a member of the Parlement of Brittany at Rennes. René lived with his grandmother and with his great-uncle. Although the Descartes family was Roman Catholic, the Poitou region was controlled by the Protestant Huguenots. In 1607, late because of his fragile health, he entered the Jesuit Collège Royal Henry-Le-Grand at La Flèche, where he was introduced to mathematics and physics, including Galileo's work. While there, Descartes first encountered hermetic mysticism. After graduation in 1614, he studied for two years (1615–16) at the University of Poitiers, earning a Baccalauréat and Licence in canon and civil law in 1616, in accordance with his father's wishes that he should become a lawyer. From there, he moved to Paris.

In Discourse on the Method, Descartes recalls:

I entirely abandoned the study of letters. Resolving to seek no knowledge other than that of which could be found in myself or else in the great book of the world, I spent the rest of my youth traveling, visiting courts and armies, mixing with people of diverse temperaments and ranks, gathering various experiences, testing myself in the situations which fortune offered me, and at all times reflecting upon whatever came my way to derive some profit from it.

DescartesGraduationRegistry
Graduation registry for Descartes at the University of Poitiers, 1616

Army service

In accordance with his ambition to become a professional military officer in 1618, Descartes joined, as a mercenary, the Protestant Dutch States Army in Breda under the command of Maurice of Nassau, and undertook a formal study of military engineering, as established by Simon Stevin. Descartes, therefore, received much encouragement in Breda to advance his knowledge of mathematics. In this way, he became acquainted with Isaac Beeckman, the principal of a Dordrecht school, for whom he wrote the Compendium of Music (written 1618, published 1650).

While in the service of the Catholic Duke Maximilian of Bavaria from 1619, Descartes was present at the Battle of the White Mountain near Prague, in November 1620.

According to Adrien Baillet, on the night of 10–11 November 1619 (St. Martin's Day), while stationed in Neuburg an der Donau, Descartes shut himself in a room with an "oven" (probably a cocklestove) to escape the cold. While within, he had three dreams, and believed that a divine spirit revealed to him a new philosophy. However, it is speculated that what Descartes considered to be his second dream was actually an episode of exploding head syndrome. Upon exiting, he had formulated analytic geometry and the idea of applying the mathematical method to philosophy. He concluded from these visions that the pursuit of science would prove to be, for him, the pursuit of true wisdom and a central part of his life's work. Descartes also saw very clearly that all truths were linked with one another, so that finding a fundamental truth and proceeding with logic would open the way to all science. Descartes discovered this basic truth quite soon: his famous "I think, therefore I am."

Career

France

In 1620, Descartes left the army. He visited Basilica della Santa Casa in Loreto, then visited various countries before returning to France, and during the next few years, he spent time in Paris. It was there that he composed his first essay on method: Regulae ad Directionem Ingenii (Rules for the Direction of the Mind). He arrived in La Haye in 1623, selling all of his property to invest in bonds, which provided a comfortable income for the rest of his life. Descartes was present at the siege of La Rochelle by Cardinal Richelieu in 1627. In the autumn of that year, in the residence of the papal nuncio Guidi di Bagno, where he came with Mersenne and many other scholars to listen to a lecture given by the alchemist, Nicolas de Villiers, Sieur de Chandoux, on the principles of a supposed new philosophy, Cardinal Bérulle urged him to write an exposition of his new philosophy in some location beyond the reach of the Inquisition.

Netherlands

Westermarkt 6, Descarteshuis (links)
In Amsterdam, Descartes lived at Westermarkt 6 (Maison Descartes, left).
Descartes-2
Title page of "Principia philosophiae" (Principles of Philosophy), 1656

Descartes returned to the Dutch Republic in 1628. In April 1629, he joined the University of Franeker, studying under Adriaan Metius, either living with a Catholic family or renting the Sjaerdemaslot. The next year, under the name "Poitevin", he enrolled at Leiden University, which at the time was a Protestant University. He studied both mathematics with Jacobus Golius, who confronted him with Pappus's hexagon theorem, and astronomy with Martin Hortensius. In October 1630, he had a falling-out with Beeckman, whom he accused of plagiarizing some of his ideas. In Amsterdam, he had a relationship with a servant girl, Helena Jans van der Strom, with whom he had a daughter, Francine, who was born in 1635 in Deventer. She was baptized a Protestant and died of scarlet fever at the age of 5.

Unlike many moralists of the time, Descartes did not deprecate the passions but rather defended them; he wept upon Francine's death in 1640. According to a recent biography by Jason Porterfield, "Descartes said that he did not believe that one must refrain from tears to prove oneself a man." Russell Shorto speculates that the experience of fatherhood and losing a child formed a turning point in Descartes' work, changing its focus from medicine to a quest for universal answers.

Despite frequent moves, he wrote all of his major work during his 20-plus years in the Netherlands, initiating a revolution in mathematics and philosophy. In 1633, Galileo was condemned by the Italian Inquisition, and Descartes abandoned plans to publish Treatise on the World, his work of the previous four years. Nevertheless, in 1637, he published parts of this work in three essays: "Les Météores" (The Meteors), "La Dioptrique" (Dioptrics) and La Géométrie (Geometry), preceded by an introduction, his famous Discours de la méthode (Discourse on the Method). In it, Descartes lays out four rules of thought, meant to ensure that our knowledge rests upon a firm foundation:

The first was never to accept anything for true which I did not know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgment than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.

In La Géométrie, Descartes exploited the discoveries he made with Pierre de Fermat. This later became known as Cartesian Geometry.

Descartes continued to publish works concerning both mathematics and philosophy for the rest of his life. In 1641, he published a metaphysics treatise, Meditationes de Prima Philosophia (Meditations on First Philosophy), written in Latin and thus addressed to the learned. It was followed in 1644 by Principia Philosophiae (Principles of Philosophy), a kind of synthesis of the Discourse on the Method and Meditations on First Philosophy. In 1643, Cartesian philosophy was condemned at the University of Utrecht, and Descartes was obliged to flee to the Hague, settling in Egmond-Binnen.

Between 1643 and 1649 Descartes lived with his girlfriend at Egmond-Binnen in an inn. Descartes became friendly with Anthony Studler van Zurck, lord of Bergen and participated in the design of his mansion and estate. He also met Dirck Rembrantsz van Nierop, a mathematician and surveyor. He was so impressed by Van Nierop's knowledge that he even brought him to the attention of Constantijn Huygens and Frans van Schooten.

Christia Mercer suggested that Descartes may have been influenced by Spanish author and Roman Catholic nun Teresa of Ávila, who, fifty years earlier, published The Interior Castle, concerning the role of philosophical reflection in intellectual growth.

Descartes began (through Alfonso Polloti, an Italian general in Dutch service) a six-year correspondence with Princess Elisabeth of Bohemia, devoted mainly to moral and psychological subjects. Connected with this correspondence, in 1649 he published Les Passions de l'âme (The Passions of the Soul), which he dedicated to the Princess. A French translation of Principia Philosophiae, prepared by Abbot Claude Picot, was published in 1647. This edition was also dedicated to Princess Elisabeth. In the preface to the French edition, Descartes praised true philosophy as a means to attain wisdom. He identifies four ordinary sources to reach wisdom and finally says that there is a fifth, better and more secure, consisting in the search for first causes.

Sweden

Dispute-of-queen-cristina-vasa-and-rene-descartes
Descartes in conversation with Queen Christina in Stockholm

By 1649, Descartes had become one of Europe's most famous philosophers and scientists. That year, Queen Christina of Sweden invited him to her court to organize a new scientific academy and tutor her in his ideas about love. Descartes accepted, and moved to the Swedish Empire in the middle of winter. She was interested in and stimulated Descartes to publish The Passions of the Soul.

He was a guest at the house of Pierre Chanut, living on Västerlånggatan, less than 500 meters from Tre Kronor in Stockholm. There, Chanut and Descartes made observations with a Torricellian mercury barometer. Challenging Blaise Pascal, Descartes took the first set of barometric readings in Stockholm to see if atmospheric pressure could be used in forecasting the weather.

Death

Descartes arranged to give lessons to Queen Christina after her birthday, three times a week at 5 am, in her cold and draughty castle. However, by 15 January 1650 the Queen actually met with Descartes only four or five times. It soon became clear they did not like each other; she did not care for his mechanical philosophy, nor did he share her interest in Ancient Greek language and literature. On 1 February 1650, he contracted pneumonia and died on 11 February at Chanut.

“Yesterday morning about four o'clock a.m. has deceased here at the house of His Excellency Mr. Chanut, French ambassador, Mr. Descartes. As I have been informed, he had been ill for a few days with pleurisy. But as he did not want to take or use medicines, a hot fever appears to have arisen as well. Thereupon, he had himself bled three times in one day, but without operation of losing much blood. Her Majesty much bemoaned his decease, because he was such a learned man. He has been cast in wax. It was not his intention to die here, as he had resolved shortly before his death to return to Holland at the first occasion. Etc.”

The cause of death was pneumonia according to Chanut, but peripneumonia according to Christina's physician Johann van Wullen who was not allowed to bleed him. (The winter seems to have been mild, except for the second half of January which was harsh as described by Descartes himself; however, "this remark was probably intended to be as much Descartes' take on the intellectual climate as it was about the weather.")

(left) The tomb of Descartes (middle, with detail of the inscription), in the Abbey of Saint-Germain-des-Prés, Paris; (right) memorial to Descartes, erected in the 1720s, in the Adolf Fredriks kyrka

E. Pies has questioned this account, based on a letter by the Doctor van Wullen; however, Descartes had refused his treatment, and more arguments against its veracity have been raised since. In a 2009 book, German philosopher Theodor Ebert argues that Descartes was poisoned by a Catholic missionary who opposed his religious views.

As a Catholic in a Protestant nation, he was interred in a graveyard used mainly for orphans in Adolf Fredriks kyrka in Stockholm. His manuscripts came into the possession of Claude Clerselier, Chanut's brother-in-law, and "a devout Catholic who has begun the process of turning Descartes into a saint by cutting, adding and publishing his letters selectively." In 1663, the Pope placed Descartes' works on the Index of Prohibited Books. In 1666, sixteen years after his death, his remains were taken to France and buried in Saint-Étienne-du-Mont. In 1671, Louis XIV prohibited all lectures in Cartesianism. Although the National Convention in 1792 had planned to transfer his remains to the Panthéon, he was reburied in the Abbey of Saint-Germain-des-Prés in 1819, missing a finger and the skull. His skull is on display in the Musée de l'Homme in Paris.

Philosophical work

Descartes3
René Descartes at work

In his Discourse on the Method, Descartes states "Cogito, ergo sum" (English: "I think, therefore I am"). He then concludes that if he doubts, then something or someone must be doing the doubting; therefore, the very fact that he doubts proves his existence.

Mind–body dualism

L'homme V00083 00000004
L'homme (1664)

Descartes began to investigate the connection between the mind and body, and how the two interact. His theory on the separation between the mind and the body, known as Cartesian dualism (or mind–body dualism), went on to influence many later Western philosophies. In Meditations on First Philosophy, Descartes states that humans are a union of mind and body and that mind and body are distinct but closely joined. According to Descartes, the mind is utterly indivisible: because "when I consider the mind, or myself in so far as I am merely a thinking thing, I am unable to distinguish any part within myself; I understand myself to be something quite single and complete."

A human was, according to Descartes, a composite entity of mind and body. Descartes gave priority to the mind and argued that the mind could exist without the body, but the body could not exist without the mind.

Physiology and psychology

In The Passions of the Soul, published in 1649, Descartes discussed the common contemporary belief that the human body contained animal spirits. These animal spirits were believed to be light and roaming fluids circulating rapidly around the nervous system between the brain and the muscles. These animal spirits were believed to affect the human soul, or passions of the soul. Descartes distinguished six basic passions: wonder, love, hatred, desire, joy and sadness. All of these passions, he argued, represented different combinations of the original spirit, and influenced the soul to will or want certain actions.

He was among the first scientists who believed that the soul should be subject to scientific investigation. He challenged the views of his contemporaries that the soul was divine, thus religious authorities regarded his books as dangerous.

On animals

Descartes denied that animals had reason or intelligence. Whereas humans had a soul, or mind, and were able to feel pain and anxiety, animals by virtue of not having a soul could not feel pain or anxiety. If animals showed signs of distress then this was to protect the body from damage, but the innate state needed for them to suffer was absent. Although Descartes' views were not universally accepted, they became prominent in Europe and North America, allowing humans to treat animals with impunity. The view that animals were quite separate from humanity and merely machines allowed for the maltreatment of animals, and was sanctioned in law and societal norms until the middle of the 19th century.

Mathematics

x for unknown; exponential notation

Descartes "invented the convention of representing unknowns in equations by x, y, and z, and knowns by a, b, and c". He also "pioneered the standard notation" that uses superscripts to show the powers or exponents; for example, the 2 used in x2 to indicate x squared.

Analytic geometry

Cartesian coordinates 2D
A Cartesian coordinates graph, using his invented x and y axes

One of Descartes' most enduring legacies was his development of Cartesian or analytic geometry, which uses algebra to describe geometry. He was first to assign a fundamental place for algebra in the system of knowledge.

Influence on Newton's mathematics

Current popular opinion holds that Descartes had the most influence of anyone on the young Isaac Newton, and this is arguably one of his most important contributions.

The basis of calculus

Descartes' work provided the basis for the calculus developed by Leibniz and Newton, who applied the infinitesimal calculus to the tangent line problem, thus permitting the evolution of that branch of modern mathematics. His rule of signs is also a commonly used method to determine the number of positive and negative roots of a polynomial.

Physics

Philosophy, metaphysics, and physics

Descartes is often regarded as the first thinker to emphasize the use of reason to develop the natural sciences. For him, philosophy was a thinking system that embodied all knowledge, as he related in a letter to a French translator:

Thus, all Philosophy is like a tree, of which Metaphysics is the root, Physics the trunk, and all the other sciences the branches that grow out of this trunk, which are reduced to three principals, namely, Medicine, Mechanics, and Ethics. By the science of Morals, I understand the highest and most perfect which, presupposing an entire knowledge of the other sciences, is the last degree of wisdom.

Mechanics

Mechanical philosophy

The beginning to Descartes' interest in physics is accredited to the amateur scientist and mathematician Isaac Beeckman, whom he met in 1618, and who was at the forefront of a new school of thought known as mechanical philosophy. With this foundation of reasoning, Descartes formulated many of his theories on mechanical and geometric physics. It is said that they met when both were looking at a placard that was set up in the Breda marketplace, detailing a mathematical problem to be solved. Descartes asked Beeckman to translate the problem from Dutch to French. In their following meetings Beeckman interested Descartes in his corpuscularian approach to mechanical theory, and convinced him to devote his studies to a mathematical approach to nature. In 1628, Beeckman also introduced him to many of Galileo's ideas. Together, they worked on free fall, catenaries, conic sections, and fluid statics. Both believed that it was necessary to create a method that thoroughly linked mathematics and physics.

Conservation of motion

In Principles of Philosophy (Principia Philosophiae) from 1644 Descartes outlined his views on the universe. In it he describes his three laws of motion. (Newton's own laws of motion would later be modeled on Descartes' exposition.) Descartes defined "quantity of motion" (Latin: quantitas motus) as the product of size and speed, and claimed that the total quantity of motion in the universe is conserved.

If x is twice the size of y, and is moving half as fast, then there's the same amount of motion in each.

[God] created matter, along with its motion ... merely by letting things run their course, he preserves the same amount of motion ... as he put there in the beginning.

Descartes had discovered an early form of the law of conservation of momentum. He envisioned quantity of motion as pertaining to motion in a straight line, as opposed to perfect circular motion, as Galileo had envisioned it. Descartes' discovery should not be seen as the modern law of conservation of momentum, since had no concept of mass as distinct from weight or size, and since he believed that it is speed rather than velocity that is conserved.

Planetary motion

Descartes' vortex theory of planetary motion was later rejected by Newton in favor of his law of universal gravitation, and most of the second book of Newton's Principia is devoted to his counterargument.

Optics

Descartes also made contributions to the field of optics. He showed by using geometric construction and the law of refraction (also known as Descartes' law, or more commonly Snell's law outside France) that the angular radius of a rainbow is 42 degrees (i.e., the angle subtended at the eye by the edge of the rainbow and the ray passing from the sun through the rainbow's centre is 42°). He also independently discovered the law of reflection, and his essay on optics was the first published mention of this law.

Meteorology

Descartes first proposed the idea that the elements were made up of small particles that join together imperfectly, thus leaving small spaces in between. These spaces were then filled with smaller much quicker "subtile matter". These particles were different based on what element they constructed, for example, Descartes believed that particles of water were "like little eels, which, though they join and twist around each other, do not, for all that, ever knot or hook together in such a way that they cannot easily be separated." In contrast, the particles that made up the more solid material, were constructed in a way that generated irregular shapes. The size of the particle also matters, if the particle was smaller, not only was it faster and constantly moving, it was more easily agitated by the larger particles, which were slow but had more force. The different qualities, such as combinations and shapes, gave rise to different secondary qualities of materials, such as temperature. This first idea is the basis for the rest of Descartes' theory on Meteorology.

Descartes theorized that when a cloud rests above another cloud and the air around the top cloud is hot, it condenses the vapor around the top cloud, and causes the particles to fall. When the particles falling from the top cloud collided with the bottom cloud's particles it would create thunder. He compared his theory on thunder to his theory on avalanches. Descartes believed that the booming sound that avalanches created, was due to snow that was heated, and therefore heavier, falling onto the snow that was below it. This theory was supported by experience "It follows that one can understand why it thunders more rarely in winter than in summer; for then not enough heat reaches the highest clouds, in order to break them up,”

Another theory that Descartes had was on the production of lightning. Descartes believed that lightning was caused by exhalations trapped between the two colliding clouds. He believed that in order to make these exhalations viable to produce lightning, they had to be made "fine and inflammable" by hot and dry weather. Whenever the clouds would collide it would cause them to ignite creating lightning, if the cloud above was heavier than the bottom cloud it would also produce thunder.

Descartes also believed that clouds were made up of drops of water and ice, and believed that rain would fall whenever the air could no longer support them. It would fall as snow if the air wasn't warm enough to melt the raindrops. And hail was when the cloud drops would melt, and then freeze again because cold air would refreeze them.

Descartes did not use mathematics or instruments (as there weren't any at the time) to back up his theories on Meteorology and instead used qualitative reasoning in order to deduce his hypothesis.

See also

Kids robot.svg In Spanish: René Descartes para niños

  • 3587 Descartes, asteroid
  • Cartesian circle
  • Cartesian doubt
  • Cartesian materialism (not a view that was held by or formulated by Descartes)
  • Descartes number
  • Cartesian plane
  • Descartes Prize
  • Descartes-Huygens Prize
  • Cartesian product
  • Cartesian product of graphs
  • Cartesian theater
  • Cartesian tree
  • Descartes crater and Highlands on the Moon (Apollo 16 landing site)
  • Descartes' rule of signs
  • Descartes's theorem (4 tangent circles)
  • Descartes' theorem on total angular defect
  • Folium of Descartes
  • Bucket argument
  • Paris Descartes University
  • List of things named after René Descartes
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