Scientists



DESCARTES
Rene Descartes (Latinized form: Renatus Cartesius; 1596 – 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, which 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 algebraic equations to be expressed as geometric shapes in a twodimensional coordinate system — 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 born in La Haye en Touraine (now Descartes), IndreetLoire, France. When he was one year old, his mother died. His father was
a member in the provincial parliament. At the age of eight, he entered the Jesuit College Royal HenryLeGrand at La Fleche. After graduation
in December 1616, he studied at the University of Poitiers, earning a Baccalaureat and Licence in law, in accordance with his father's wishes
that he should become a lawyer.
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 fallingout with Beeckman, whom he accused of plagiarizing some of his ideas.
Despite these frequent moves he wrote all his major work during his 20plus 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: "The Meteors", "Dioptrics"
and "Geometry", preceded by an introduction, his famous "Discourse on the Method". In it Descartes lays out four rules of thought, meant to
ensure that our knowledge rests upon a firm foundation.
Descartes continued to publish works concerning both mathematics and philosophy for the rest of his life. In 1641 he published a metaphysics
work, "Meditations on First Philosophy", written in Latin and thus addressed to the learned. It was followed, in 1644, by "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 "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 EgmondBinnen in 1648.
A French translation of "Principles of Philosophy", 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.
Rene 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".
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 4 used in x^{4}
to indicate squaring of squaring. He was first to assign a fundamental place for algebra in our system of knowledge, and believed that algebra
was 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
a^{2} could represent length as well as an area. This was in opposition to the teachings of mathematicians, such as Viete, who
argued that it could represent only area. Although Descartes did not pursue the subject, he preceded 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's law or more commonly Snell's law, who discovered it 16 years earlier) 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.
Although Descartes was well known in academic circles towards the end of his life, the teaching of his works in schools was controversial.
Henri de Roy (1598–1679), Professor of Medicine at the University of Utrecht, was condemned by the Rector of the University, Gijsbert Voet,
for teaching Descartes's physics.
