Prosecution by Roman Inquisition, 1633
Descartes's Method of Doubt. Knowledge is defined by its irrefutable certainty. Therefore, press
doubt as far as it can be, and anything that is discovered to be indubitable must be counted as
Knowledge: requires certainty; a clear, distinct, irrefutable judgment.
The senses are uncertain (evidence of dreams and illusions)
Reasoning can be doubted (the argument about God and the possibility of error)
The ―Cogito‖— the thought ―I am, I exist‖ cannot be false whenever one thinks it.
―Cogito ergo sum‖—why is this significant?
1. Proves that knowledge is possible in principle
2. Provides a test or criterion of truth. A clear and distinct idea (like the Cogito) is true.
Mind (soul, thought, consciousness) is an immaterial substance whose essence it is to think (a res
cogitans, a thinking thing).
Essence of matter is spatial extension, determinate spatial measure.
Implications of this concept of the essence of matter:
1. Primary and Secondary Qualities
Primary: qualities all bodies share just as bodies: shape, size, weight, and so on.
Secondary: Qualities arising from interaction with perception: color, taste, odor, and so on.
2. Plenum. The universe is one continuous body. No empty space. 3. Inert matter. Motion is not a primary quality of matter. Motion occurs only by impact.
4. Mind-Body problem. How do the two essentially different substances (mind as immaterial,
body as spatial) interact ené Descartes ( French:[ʁəne dekaʁt]; Latinized form: Renatus Cartesius; adjectival form:
"Cartesian";31 March 1596 – 11 February 1650) was a French philosopher, mathematician,
and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the
'Father of Modern Philosophy', and much subsequent Western philosophy is a response to his
writings,[8which are studied closely to this day. In particular, his Meditations on First
Philosophy continues to be a standard text at most university philosophy departments. Descartes'
influence in mathematics is equally apparent; the Cartesian coordinate system — allowing
reference to a point in space as a set of numbers, and allowing algebraic equations to be
expressed as geometric shapes in a two-dimensional coordinate system (and conversely, shapes
to be described as equations) — was named after him. He is credited as the father of analytical
geometry, the bridge between algebra and geometry, crucial to the discovery of infinitesimal
calculus and analysis. Descartes was also one of the key figures in the Scientific Revolution and
has been described as an example of genius.
Descartes frequently sets his views apart from those of his predecessors. In the opening section
of the Passions of the Soul, a treatise on the Early Modern version of what are now commonly
called emotions, Descartes goes so far as to assert that he will write on this topic "as if no one
had written on these matters before". Many elements of his philosophy have precedents in late
Aristotelianism, the revived Stoicism of the 16th century, or in earlier philosophers like St.
Augustine. In his natural philosophy, he differs from the schools on two major points: First, he
rejects the analysis of corporeal substance into matter and form; second, he rejects any appeal to
ends—divine or natural—in explaining natural phenomena. In his theology, he insists on the
absolute freedom of God's act of creation.
Descartes was a major figure in 17th-century continental rationalism, later advocated by Baruch
Spinoza and Gottfried Leibniz, and opposed by the empiricist school of thought consisting of
Hobbes, Locke, Berkeley, Jean-Jacques Rousseau, and Hume. Leibniz, Spinoza and Descartes
were all well versed in mathematics as well as philosophy, and Descartes and Leibniz
contributed greatly to science as well.
He is perhaps best known for the philosophical statement "Cogito ergo sum" (French: Je pense,
donc je suis; English: I think, therefore I am), found in part IV of Discourse on the Method (1637
– written in French but with inclusion of "Cogito ergo sum") and §7 of part I of Principles of
Philosophy (1644 – written in Latin).
o 1.1 Religious beliefs
2 Philosophical work
o 2.1 Dualism
o 2.2 Descartes' moral philosophy
3 Historical impact
o 3.1 Emancipation from Church doctrine
o 3.2 Mathematical legacy
o 3.3 Contemporary reception 4 Writings
5 See also
o 7.1 References
o 7.2 Collected works
o 7.3 Collected English translations
o 7.4 Single works
o 7.5 Secondary literature
8 External links
Graduation registry for Descartes at the Collège Royal Henry-Le-Grand, La Flèche, 1616
Descartes was born in La Haye en Touraine (now Descartes), Indre-et-Loire, France. When he
was one year old, his mother Jeanne Brochard died. His father Joachim was a member of the
Parlement of Brittany at Rennes. In 1606 or 1607 he entered the Jesuit Collège Royal Henry-
Le-Grand at La Flèche [11where he was introduced to mathematics and physics, including
Galileo's work. After graduation in December 1616, he studied at the University of Poitiers,
earning a Baccalauréat and Licence in law, in accordance with his father's wishes that he should
become a lawyer. 
"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 so as to derive some profit from it."
(Descartes, Discourse on the Method). In 1618, Descartes was engaged in the army of Maurice of Nassau in the Dutch Republic, but as
a truce had been established between Holland and Spain, Descartes used his spare time to study
mathematics. In this way he became acquainted with Isaac Beeckman, principal of Dordrecht
school. Beeckman had proposed a difficult mathematical problem, and to his astonishment, it
was the young Descartes who found the solution. Both believed that it was necessary to create a
method that thoroughly linked mathematics and physics. While in the service of the Duke
Maximilian of Bavaria, Descartes was present at the Battle of the White Mountain outside
Prague, in November 1620.
On the night of 10–11 November 1619, while stationed in Neuburg an der Donau, Germany,
Descartes experienced a series of three powerful dreams or visions that he later claimed
profoundly influenced his life. 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. This basic truth, Descartes
found quite soon: his famous "I think". 
In 1622 he returned to France, and during the next few years spent time in Paris and other parts
of Europe. It was during a stay in Paris 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.
He returned to the Dutch Republic in 1628, where he lived until September 1649. In April 1629
he joined the University of Franeker, living at the Sjaerdemaslot, and the next year, under the
name "Poitevin", he enrolled at the Leiden University to study mathematics with Jacob Golius
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, at which time Descartes taught at the Utrecht University. Francine
Descartes died in 1640 in Amersfoort, from Scarlet Fever.
While in the Netherlands he changed his address frequently, living among other places in
Dordrecht (1628), Franeker (1629), Amsterdam (1629–30), Leiden (1630), Amsterdam (1630–
32), Deventer (1632–34), Amsterdam (1634–35), Utrecht (1635–36), Leiden (1636), Egmond
(1636–38), Santpoort (1638–1640), Leiden (1640–41), Endegeest (a castle near Oegstgeest)
(1641–43), and finally for an extended time in Egmond-Binnen (1643–49).
Despite these frequent moves he wrote all his major work during his 20-plus years in the
Netherlands, where he managed to revolutionize mathematics and philosophy. In 1633, Galileo
was condemned by the Roman Catholic Church, and Descartes abandoned plans to publish
Treatise on the World, his work of the previous four years. Nevertheless, in 1637 he published
part 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 Métode
(Discourse on the Method). In it Descartes lays out four rules of thought, meant to ensure that
our knowledge rests upon a firm foundation. René Descartes (right) with Queen Christina of Sweden (left).
Descartes continued to publish works concerning both mathematics and philosophy for the rest
of his life. In 1641 he published a metaphysics work, Meditationes de Prima Philosophia
(Meditations on First Philosophy), written in Latin and thus addressed to the learned. It was
followed, in 1644, by Principia Philosophiæ (Principles of Philosophy), a kind of synthesis of
the Meditations and the Discourse. In 1643, Cartesian philosophy was condemned at the
University of Utrecht, and Descartes began his long 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 (Passions of the Soul), that he
dedicated to the Princess. In 1647, he was awarded a pension by the King of France. Descartes
was interviewed by Frans Burman at Egmond-Binnen in 1648.
A French translation of Principia Philosophiæ, prepared by Abbot Claude Picot, was published
in 1647. This edition Descartes dedicated to Princess Elisabeth of Bohemia. In the preface
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.19]
René Descartes died on 11 February 1650 in Stockholm, Sweden, where he had been invited as a
tutor for Queen Christina of Sweden. The cause of death was said to be pneumonia; accustomed
to working in bed until noon, he may have suffered damage to his health from Christina's
demands for early morning study (the lack of sleep could have severely compromised his
immune system). Descartes stayed at the French ambassador Pierre Chanut.
In 1663, the Pope placed his works on the Index of Prohibited Books. The tomb of Descartes (middle, with detail of the inscription), in the Abbey of Saint-Germain-
As a Roman Catholic in a Protestant nation, he was interred in a graveyard used mainly for
unbaptized infants in Adolf Fredriks kyrka in Stockholm. Later, his remains were taken to France
and buried in the Abbey of Saint-Germain-des-Prés in Paris. Although the National Convention
in 1792 had planned to transfer his remains to the Panthéon, they are, two centuries later, still
resting between two other graves — those of the scholarly monks Jean Mabillon and Bernard de
Montfaucon — in a chapel of the abbey. His memorial, erected in the 18th century, remains in
the Swedish church.
The religious beliefs of René Descartes have been rigorously debated within scholarly circles. He
claimed to be a devout Roman Catholic, claiming that one of the purposes of the Meditations
was to defend the Christian faith. However, in his own era, Descartes was accused of harboring
secret deist or atheist beliefs. Contemporary Blaise Pascal said that "I cannot forgive Descartes;
in all his philosophy, Descartes did his best to dispense with God. But Descartes could not avoid
prodding God to set world in motion with a snap of his lordly fingers; after that, he had no
more use for God."
Stephen Gaukroger's biography of Descartes reports that "he had a deep religious faith as a
Catholic, which he retained to his dying day, along with a resolute, passionate desire to discover
the truth." After Descartes died in Sweden, Queen Christina abdicated her throne to convert to
Roman Catholicism (Swedish law required a Protestant ruler). The only Roman Catholic with
whom she had prolonged contact was Descartes, who was her personal tutor. 
Descartes is often regarded as the first thinker to emphasize the use of reason to develop the