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DESCARTES, RENÉ DU PERRON (b. La Haye,
Touraine, France, 31 March 1596; d. Stockholm,
Sweden, 11 February 1650), natural philosophy, scientific
method, mathematics, optics, mechanics, physiology.
the influential Cardinal de Bérulle, who a few days
later charged him to devote his life to working out
the application of “his manner of philosophizing ...
to medicine and mechanics. The one would contribute
to the restoration and conservation of health, and the
other to some diminution and relief in the labours of
mankind.”4 To execute this design he withdrew, toward
the end of the year, to the solitary life in the
Netherlands which he lived until his last journey to
Stockholm in 1649, where, as Queen Christina's
philosopher, he died in his first winter.
The primarily centrifugal direction of Descartes's
thought, moving out into detailed phenomena from
a firm central theory (in contrast with the more empirical
scientific style of Francis Bacon and Newton),
is shown by the sequence of composition of his major
writings. He set out his method in the Rules for the
Direction of the Mind, left unfinished in 1628 and
published posthumously, and in the Discours de la
méthode, written in the Netherlands along with the
Météores, La dioptrique, and La
géométrie, which he
presented as examples of the method. All were published
in one volume in 1637. At the same time his
investigation into the true ontology led him to the
radical division of created existence into matter as
simply extended substance, given motion at the creation,
and mind as unextended thinking substance.
This conclusion he held to be guaranteed by the perfection
of God, who would not deceive true reason.
How these two mutually exclusive and collectively
exhaustive categories of substance could have any
interaction in the embodied soul that was a man was
a question discussed between Gassendi, Hobbes, and
Descartes in the Objections and Replies published
with his Meditations on First Philosophy in 1641.
It was from these first principles that he had given
an account in Le monde, ou Traité de la lumière of
cosmogony
and cosmology as products simply of matter
in motion, making the laws of motion the ultimate
“laws of nature” and all scientific explanation ultimately
mechanistic. This treatise remained unpublished
in Descartes's lifetime. So too did the
associated treatise L'homme, in which he represented
animals and the human body as sheer mechanisms,
an idea already found in the Rules. He withheld these
essays, on the brink of publication, at the news of
Galileo's condemnation in 1633, and instead published
his general system of physics, with its Copernicanism
mitigated by the idea that all motion is relative, in
the Principles of Philosophy in 1644. Finally, he
brought physiological psychology within the compass
of his system in Les passions de l'âme in 1649. This
system aimed to be as complete as Aristotle's, which
it was designed to replace. It was not by chance that
it dealt in the same order with many of the same
phenomena (such as the rainbow), as well as with
others more recently investigated (such as magnetism).
A comparison of Descartes's performance with his
program of scientific method presents a number of
apparent contradictions. He made much of the ideal
of a mathematically demonstrated physics, yet his
fundamental cosmology was so nearly entirely qualitative
that he came to fear that he had produced
nothing more than a beautiful “romance of nature.”5
His planetary dynamics was shown by Newton to be
quantitatively ridiculous. He wrote in the Discours,
“I noticed also with respect to experiments
[expériences]
that they become so much the more necessary,
the more we advance in knowledge,”6 yet his fundamental
laws of nature, the laws of motion and impact,
had to be dismantled by Huygens and Leibniz for
their lack of agreement with observation. These apparent
contradictions may be resolved in the contrast
between Descartes's theoretical ideal of completed
scientific knowledge and the actual process and circumstances
of acquiring such knowledge. For the
modern reader to pay too much attention to his
mechanics and to the Principles, a premature conception
of completed science, can obscure Descartes's
firm grasp of the necessity for observation and experiment
already expressed in the Rules in his
criticism “of those philosophers who neglect experiments
and expect truth to rise from their own heads
like Minerva from Jupiter's.”7
No other great philosopher, except perhaps Aristotle,
can have spent so much time in experimental
observation. According to Baillet, over several years
he studied anatomy, dissected and vivisected embryos
of birds and cattle, and went on to study chemistry.
His correspondence from the Netherlands described
dissections of dogs, cats, rabbits, cod, and mackerel;
eyes, livers, and hearts obtained from an abattoir;
experiments on the weight of the air and on vibrating
strings; and observations on rainbows, parahelia, and
other optical phenomena. Many of his scientific writings
reflect these activities and show sound experimental
knowledge, although the extreme formalism
of his physiological models obscures the question of
his actual knowledge of some aspects of anatomy.
Attention to the whole range of his scientific thought
and practice shows a clear conception not only of
completed scientific knowledge but also of the roles
of experiment and hypothesis in making discoveries
and finding explanations by which the body of scientific
knowledge was built up.
Descartes's conception of completed scientific
knowledge was essentially that envisaged by Aristotle's
true scientific demonstration. It was the geometers'