René Descartes
FRENCH
MATHEMATICIAN AND PHILOSOPHER
René Descartes, (born March 31, 1596, La
Haye, Touraine, France—died February
11, 1650, Stockholm,
Sweden), French mathematician, scientist, and philosopher. Because he was one
of the first to abandon scholastic Aristotelianism, because he
formulated the first modern version of mind-body dualism, from which stems the mind-body problem, and because he promoted the
development of a new science grounded in
observation and experiment, he has been called the father of modern philosophy.
Applying an original system of methodical doubt, he dismissed apparent
knowledge derived from authority, the senses, and reason and erected new
epistemic foundations on the basis of the intuition that,
when he is thinking, he
exists; this he expressed in the dictum “I think, therefore I am” (best known
in its Latin formulation, “Cogito, ergo sum,” though
originally written in French, “Je pense, donc je suis”). He developed a metaphysical dualism that
distinguishes radically between mind, the essence of which is thinking, and
matter, the essence of which is extension in three dimensions.
Descartes’s metaphysics is
rationalist, based on the postulation of innate ideas of mind,
matter, and God, but his physics and physiology, based on sensory experience,
are mechanistic and empiricist.
Early Life And Education
René du Perron Descartes was born
in La Haye en Touraine (now Descartes,
Indre-et-Loire), France, on 31 March 1596. His mother, Jeanne
Brochard, died soon after giving birth to him, and so he was not expected to
survive. 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. 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 his book 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
travelling, 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.
Given 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). Together they worked on free fall, catenary, conic
section, and fluid statics. Both believed that it was necessary to
create a method that thoroughly linked mathematics and physics.
While in the service of the Catholic Duke Maximilian of Bavaria since
1619, Descartes was present at the Battle of the White Mountainoutside Prague, in
November 1620.
Philosophical Work
Initially, Descartes arrives at
only a single principle: thought exists. Thought cannot be separated from me,
therefore, I exist (Discourse on the Method and Principles
of Philosophy). Most famously, this is known as cogito ergo sum (English:
"I think, therefore I am"). Therefore, Descartes concluded, if he
doubted, then something or someone must be doing the doubting, therefore the
very fact that he doubted proved his existence. "The simple meaning of the
phrase is that if one is skeptical of existence, that is in and of itself proof
that he does exist."
Descartes concludes that he can be
certain that he exists because he thinks. But in what form? He perceives his
body through the use of the senses; however, these have previously been
unreliable. So Descartes determines that the only indubitable knowledge is that
he is a thinking thing. Thinking is what he does, and his power
must come from his essence. Descartes defines "thought" (cogitatio)
as "what happens in me such that I am immediately conscious of it, insofar
as I am conscious of it". Thinking is thus every activity of a person of
which the person is immediately conscious. He
gave reasons for thinking that waking thoughts are distinguishable from dreams,
and that one's mind cannot have been "hijacked" by an evil demon placing
an illusory external world before one's senses.
And so something that I thought I was
seeing with my eyes is in fact grasped solely by the faculty of judgment which
is in my mind.
In this manner, Descartes proceeds to
construct a system of knowledge, discarding perception as
unreliable and, instead, admitting only deduction as a method.
Dualism
Descartes, influenced by the automatons on
display throughout the city of Paris, began to investigate the connection
between the mind and body, and how the two interact. His main influences
for dualism were theology and physics. The
theory on the dualism of mind and body is Descartes' signature doctrine and
permeates other theories he advanced. Known as Cartesian dualism,
his theory on the separation between the mind and the body went on to influence
subsequent Western philosophies. In Meditations on First Philosophy Descartes
attempted to demonstrate the existence of God and the
distinction between the human soul and the body. Humans are a union of mind and
body, thus Descartes' dualism embraced the idea that mind and body are
distinct but closely joined. While many contemporary readers of Descartes found
the distinction between mind and body difficult to grasp, he thought it was
entirely straightforward. Descartes employed the concept of modes,
which are the ways in which substances exist. In Principles of Philosophy Descartes
explained "we can clearly perceive a substance apart from the mode which
we say differs from it, whereas we cannot, conversely, understand the mode
apart from the substance". To perceive a mode apart from its substance
requires an intellectual abstraction, which Descartes explained as follows:
"The intellectual abstraction
consists in my turning my thought away from one part of the contents of this
richer idea the better to apply it to the other part with greater attention.
Thus, when I consider a shape without thinking of the substance or the
extension whose shape it is, I make a mental abstraction."[
According to Descartes two substances
are really distinct when each of them can exist apart from the other. Thus
Descartes reasoned that God is distinct from humans, and the body and mind of a
human are also distinct from one another. He argued that the great differences
between body and mind make the two always divisible. But that the mind was
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."[
In Meditations Descartes
discussed a piece of wax and
exposed the single most characteristic doctrine of Cartesian dualism: that the
universe contained two radically different kinds of substances - the mind or
soul defined as thinking, and the body defined as matter and
unthinking. The Aristotelian philosophy of Descartes' days
held that the universe was inherently purposeful or theological. Everything
that happened, be it the motion of the stars or the growth
of a tree, was
supposedly explainable by a certain purpose, goal or end that worked its way
out within nature. Aristotle called this the "final cause", and these
final causes were indispensable for explaining the ways nature operated. With
his theory on dualism Descartes fired the opening shot for the battle between
the traditional Aristotelian science and the new science of Kepler and Galileo which
denied the final cause for explaining nature. Descartes' dualism provided the philosophical
rationale for the latter and he expelled the final cause from the physical
universe (or res extensa). For Descartes the only place left for
the final cause was the mind (or res cogitans). Therefore, while
Cartesian dualism paved the way for modern physics,
it also held the door open for religious beliefs about the immortality of
the soul.
Descartes' dualism of mind and matter
implied a concept of human beings. 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. In Meditations Descartes even argues that
while the mind is a substance, the body is composed only of
"accidents". But he did argue that mind and body are closely
joined, because:
"Nature also teaches me, by the
sensations of pain, hunger, thirst and so on, that I am not merely present in
my body as a pilot in his ship, but that I am very closely joined and, as it
were, intermingled with it, so that I and the body form a unit. If this were
not so, I, who am nothing but a thinking thing, would not feel pain when the
body was hurt, but would perceive the damage purely by the intellect, just as a
sailor perceives by sight if anything in his ship is broken.
Descartes' discussion on embodiment
raised one of the most perplexing problems of his dualism philosophy: What
exactly is the relationship of union between the mind and the body of a person? Therefore,
Cartesian dualism set the agenda for philosophical discussion of the mind–body problem for many years after
Descartes' death. Descartes was also a rationalist and
believed in the power of innate ideas.
Descartes argued the theory of innate knowledge and
that all humans were born with knowledge through the higher power of God. It
was this theory of innate knowledge that later led philosopher John Locke (1632-1704)
to combat the theory of empiricism, which held that all knowledge is
acquired through experience.
Descartes on physiology and
psychology
In The Passions of the Soul written
between 1645 and 1646 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, and served as a metaphor for feelings, like
being in high or bad spirit. 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 argued, for example, that fear is a passion that moves the soul to
generate a response in the body. In line with his dualist teachings on the
separation between the soul and the body, he hypothesized that some part of the
brain served as a connector between the soul and the body and singled out
the pineal gland as connector.[ Descartes
argued that signals passed from the ear and the eye to the pineal gland,
through animal spirits. Thus different motions in the gland cause various
animal spirits. He argued that these motions in the pineal gland are based on
God's will and that humans are supposed to want and like things that are useful
to them. But he also argued that the animal spirits that moved around the body
could distort the commands from the pineal gland, thus humans had to learn how
to control their passions.
Descartes advanced a theory on
automatic bodily reactions to external events which influenced 19th
century reflex theory.
He argued that external motions such as touch and sound reach the endings of
the nerves and affect the animal spirits. Heat from fire affects a spot on the
skin and sets in motion a chain of reactions, with the animal spirits reaching
the brain through the central nervous system, and in turn animal spirits are
sent back to the muscles to move the hand away from the fire. Through this
chain of reactions the automatic reactions of the body do not require a thought
process.
Above all 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. Descartes' writings
went on to form the basis for theories on emotions and
how cognitive evaluations
were translated into affective processes. Descartes believed that the brain
resembled a working machine and unlike many of his contemporaries 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 Nobel Prize winning physiologist Ivan Pavlov was
a great admirer of Descartes.[80]
Three types of ideas
There are three kinds of ideas, Descartes
explained: Fabricated, Innate, and Adventitious. Fabricated ideas are
inventions made by the mind. For example, a person has never eaten moose but
assumes it tastes like cow. Adventitious ideas are ideas that cannot be
manipulated or changed by the mind. For example, a person stands in a cold
room, they can only think of the feeling as cold and nothing else. Innate ideas
are set ideas made by God in a person’s mind. For example, the features of a
shape can be examined and set aside, but its content can never be manipulated
to cause it not to be a three sided object.
Descartes' moral philosophy
For Descartes, ethics was
a science, the highest and most perfect of them. Like the rest of the sciences,
ethics had its roots in metaphysics. In this way, he argues for the
existence of God, investigates the place of man in nature, formulates the
theory of mind-body dualism, and defends free will.
However, as he was a convinced rationalist, Descartes clearly states that
reason is sufficient in the search for the goods that we should seek, and virtue consists
in the correct reasoning that should guide our actions. Nevertheless, the
quality of this reasoning depends on knowledge, because a well-informed mind
will be more capable of making good choices,
and it also depends on mental condition. For this reason, he said that a
complete moral philosophy should include the study of the body. He discussed
this subject in the correspondence with Princess Elisabeth of Bohemia,
and as a result wrote his work The Passions of the Soul, that
contains a study of the psychosomatic processes
and reactions in man, with an emphasis on emotions or passions. His works about
human passion and emotion would be the basis for the philosophy of his
followers, (see Cartesianism), and would have a lasting impact
on ideas concerning what literature and art should be, specifically how it
should invoke emotion.
Humans should seek the sovereign good that
Descartes, following Zeno, identifies with virtue, as this produces
a solid blessedness or pleasure.
For Epicurus the
sovereign good was pleasure, and Descartes says that, in fact, this is not in
contradiction with Zeno's teaching, because virtue produces a spiritual
pleasure, that is better than bodily pleasure. Regarding Aristotle's
opinion that happiness depends on the goods of fortune, Descartes does not deny
that this good contributes to happiness but remarks that they are in great
proportion outside one's own control, whereas one's mind is under one's
complete control. The moral writings of Descartes came at the last part of his
life, but earlier, in his Discourse on the Method he adopted
three maxims to be able to act while he put all his ideas into doubt. This is
known as his "Provisional Morals".
Descartes and natural science
Descartes is often regarded as the
first thinker to emphasize the use of reason to develop the natural sciences. For
him the philosophy was a thinking system that embodied all knowledge, and
expressed it in this way:
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.
In his Discourse on the Method,
he attempts to arrive at a fundamental set of principles that one can know as
true without any doubt. To achieve this, he employs a method called
hyperbolical/metaphysical doubt, also sometimes referred to as methodological scepticism:
he rejects any ideas that can be doubted and then re-establishes them in order
to acquire a firm foundation for genuine knowledge. Descartes built his ideas
from scratch. He relates this to architecture: the top soil is taken away to
create a new building or structure. Descartes calls his doubt the soil and new
knowledge the buildings. To Descartes, Aristotle’s foundationalism is
incomplete and his method of doubt enhances foundationalism.
Descartes on animals
Descartes denied that animals had
reason or intelligence. He argued that animals did not lack sensations or
perceptions, but these could be explained mechanistically. 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. The publications of Charles Darwin would
eventually erode the Cartesian view of animals. Darwin argued that the
continuity between humans and other species opened the possibilities that
animals did not have dissimilar properties to suffer.
Mathematical legacy
One of Descartes' most enduring
legacies was his development of Cartesian or analytic geometry, which uses
algebra to describe geometry. He "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.[103][104] He
was first to assign a fundamental place for algebra in our system of knowledge,
using it as a method to automate or mechanize reasoning, particularly about
abstract, unknown quantities. European mathematicians had previously viewed
geometry as a more fundamental form of mathematics, serving as the foundation
of algebra. Algebraic rules were given geometric proofs by mathematicians such
as Pacioli, Cardan, Tartaglia and Ferrari.
Equations of degree higher than the third were regarded
as unreal, because a three-dimensional form, such as a cube, occupied the
largest dimension of reality. Descartes professed that the abstract
quantity a2 could represent length as well as an
area. This was in opposition to the teachings of mathematicians, such as Vieta, who argued that it could represent only
area. Although Descartes did not pursue the subject, he preceded Gottfried Wilhelm Leibniz in envisioning a
more general science of algebra or "universal mathematics," as a
precursor to symbolic logic, that could encompass logical
principles and methods symbolically, and mechanize general reasoning.
Descartes' work provided the basis for
the calculus developed
by Newton and Leibniz, who applied
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.
Descartes discovered an early form of
the law of conservation of mechanical momentum (a
measure of the motion of an object), and envisioned it as pertaining to motion
in a straight line, as opposed to perfect circular motion, as Galileo had
envisioned it. He outlined his views on the universe in his Principles of Philosophy.
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)
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.
Final
Years And Heritage
In 1644, 1647, and 1648, after 16 years in the
Netherlands, Descartes returned to France for brief visits on financial
business and to oversee the translation into French of the Principles, the Meditations, and
the Objections
and Replies. (The translators were, respectively, Picot, Charles
d’Albert, duke de Luynes, and Claude Clerselier.) In 1647 he also
met with Gassendi and Hobbes, and he suggested to Pascal the famous experiment of
taking a barometer up Mount Puy-de-Dôme to determine the influence of the
weight of the air. Picot returned with Descartes to the Netherlands for the
winter of 1647–48. During Descartes’s final stay in Paris in 1648, the French nobility
revolted against the crown in a series of wars known as the Fronde. Descartes left precipitously
on August 17, 1648, only days before the death of his old
friend Mersenne.
Clerselier’s brother-in-law, Hector Pierre Chanut, who was French resident
in Sweden and later ambassador, helped to procure a pension for Descartes from Louis XIV,
though it was never paid. Later, Chanut engineered an invitation for Descartes
to the court of Queen Christina,
who by the close of the Thirty Years’ War (1618–48) had
become one of the most important and powerful monarchs in Europe. Descartes
went reluctantly, arriving early in October 1649. He may have gone because he
needed patronage; the Fronde seemed to have destroyed his chances in Paris, and
the Calvinist theologians were harassing him in the Netherlands.
In Sweden—where, Descartes said, in winter men’s thoughts freeze like the
water—the 22-year-old Christina perversely made the 53-year-old Descartes rise
before 5:00 AM to
give her philosophy lessons, even though she knew of his habit of lying in bed
until 11 o’clock in the morning. She also is said to have ordered him to write
the verses of a ballet, The
Birth of Peace (1649), to celebrate her role in the Peace of Westphalia, which ended the
Thirty Years’ War. The verses in fact were not written by Descartes, though he
did write the statutes for a Swedish Academy of Arts and Sciences. While
delivering these statutes to the queen at 5:00 AM on
February 1, 1650, he caught a chill, and he soon developed pneumonia. He died
in Stockholm on February 11. Many pious last words have been attributed to him,
but the most trustworthy report is that of his German valet, who said that
Descartes was in a coma and died without saying anything at all.
Descartes’s papers came into the possession of Claude
Clerselier, a pious Catholic, who began the process of turning Descartes into a
saint by cutting, adding to, and selectively publishing his letters. This
cosmetic work culminated in 1691 in the massive biography by Father Adrien Baillet,
who was at work on a 17-volume Lives of the Saints. Even during
Descartes’s lifetime there were questions about whether he was a Catholic
apologist, primarily concerned with supporting Christian doctrine, or an
atheist, concerned only with protecting himself with pious sentiments while establishing a
deterministic, mechanistic, and materialistic physics.
These questions remain difficult to answer, not least because all the
papers, letters, and manuscripts available to Clerselier and Baillet are now
lost. In 1667 the Roman
Catholic church made its own decision by putting Descartes’s
works on the Index Librorum Prohibitorum (Latin:
“Index of Prohibited Books”) on the very day his bones were ceremoniously
placed in Sainte-Geneviève-du-Mont in Paris. During his lifetime, Protestant
ministers in the Netherlands called Descartes a Jesuit and a papist—which is to
say an atheist. He retorted that they were intolerant, ignorant bigots.
Up to about 1930, a majority of scholars, many of whom were religious, believed
that Descartes’s major concerns were metaphysical and religious. By the late
20th century, however, numerous commentators had come to believe that Descartes
was a Catholic in the same way he was a Frenchman and a royalist—that is, by
birth and by convention.
Descartes himself said that good sense is destroyed when one thinks too
much of God. He once told a German protégée, Anna Maria van Schurman (1607–78),
who was known as a painter and a poet, that she was wasting her intellect
studying Hebrew and theology. He also was perfectly aware
of—though he tried to conceal—the atheistic potential of his materialist
physics and physiology. Descartes seemed indifferent to the emotional depths of religion.
Whereas Pascal trembled when he looked into the infinite universe and perceived the
puniness and misery of man, Descartes exulted in the power of human reason to
understand the cosmos and to promote happiness, and he rejected the view that
human beings are essentially miserable and sinful. He held that it is
impertinent to pray to God to change things. Instead, when we cannot change the
world, we must change ourselves.
