Dr.
Ari Santas’ Notes on
Introduction
to Rene Descartes
A.
Biography
(1596-1650)
-Descartes was born in 1596 in La Haye, France
-his health was frail early in
life; luckily, he had parents with enough money and sympathy to let him just
lie around in bed in the mornings
-this began an important habit of
daily reflection and meditation
-early
education was at La Fleche, a
small Jesuit college where he received training in the
Scholastic--Aristotelian--tradition
-later he studied law at the University of Poitiers
-generally, it is said that Descartes
admired his teachers but rejected most of what they taught him
-with
one notable exception--mathematics
-in 1618 he joined the army and
did a lot of traveling abroad (minus combat)
-in Nov. 1619 (still in the army),
while meditating on the uncertainty of his knowledge and on the certainty of
Mathematics, Descartes had a flash of insight
-it revealed to him how certainty
is to be gained in the sciences
-that night he had a series of
dreams that he interpreted as a divine sign that he was on the right track
-during the 1620's he, being
frustrated with initial attempts to work out the details of his new science,
decided to live it up for a while (gambling, etc.)
-around 1629, at the advice of
some friends, he went to the Dutch Republic and began
a serious attempt to set his ideas to paper
-1634 Le Monde--suppressed
because of Galileo's condemnation (he burned it)
-1637 Discourse on Method
-1641 Meditations on First Philosophy
-1644 Principles of Philosophy
-in 1649, the young Queen Christina of
Sweden asks Descartes to come to Stockholm and instruct her in philosophy and
mathematics (some say something else too)
-reluctantly, and against the
advice of friends, he accepts the offer
-due to her rigorous schedule
(which included appointments before dawn) and to his frail health (and some say
to something else) in the year 1650 he contracted pneumonia and died
-Descartes had been very
dissatisfied with the state of scientific knowledge in his time
-like a house built haphazardly
on an unstable foundation, science was a patchwork of theory and observation, a
little here, a little there, with no order or a sense of reliability
-Descartes felt that the time had
come to raze the house and start again
-but what
materials to use?
and in what order?
-in contrast to physical science,
mathematics was a highly developed discipline which proceeded step by step,
losing no certainty in moving from one idea to the next
-Descartes' dream was to find a
way to combine the certainty of mathematics with the study of physical reality
-for him, probability in the
sciences is not enough
-making his discovery would clear
the ground for his reconstruction
-the answer to his prayers was a realization
that if one could find a means of representing the motions of bodies
mathematically, then one could derive results about matter with the same kind
of certainty that one could find in pure math
-such a realization amounted to
this (something Galileo
apparently said):
-the book of nature is written in
the language of mathematics
-one of
his tasks, then, was to show how matter could be represented mathematically
-to do this he invented analytic
geometry
-it was his belief (and dream)
that eventually everything in the world could be known mathematically, and not
only that:
-that every event, past, present,
or future could be demonstrated a priori, right down to today's weather
report
-Descartes' means of combining
math and physics and of separating the physical sciences from uncertainty and
disarray was to posit a metaphysics
of dualism
-there are two distinctly
different types of substances:
mental, thinking substances and physical, non-thinking substances
-mind, or, mental substance, is
indivisible, unextended, and immortal
-body, or, physical substance is
divisible, extended, and changeable
-such a conception was useful for
two kinds of reasons:
-first,
it allowed Descartes to assuage the Church at least with respect to morals
-there is no need to experiment
and question the moral maxims offered by traditional Christianity
-science could divorce itself
from moral and value oriented questions
-second,
Descartes could now remove final causes--a source of great specious speculation
in science--from the cosmic picture and look at the world mechanically
-once we can describe the world
as a mechanism, we can then define objects and their motions mathematically and
crank out results with the same rigor as the theoretical math of the Greeks
-one should note, however, that
there is a third element in Descartes’ universe: God
-technically, then, Descartes’
universe is not a dualism but a triadism
-though later on many will drop
the God hypothesis and will be left with a dualism
-God will be invoked throughout Descartes’
metaphysics when the
going gets tough (somewhat reminiscent of St. Augustine's Confessions)
-along with a Dualism in metaphysics came a dualism
in epistemology
-our interaction with the world
takes place either through the senses, or through the intellect
-for Descartes, the senses are
part of our bodies and are therefore disjoined from the mind
-the intellect, on the other
hand, comprises the essence of mind
-it is Descartes' belief that the
senses are unreliable means of understanding nature, and knowledge can only
come from the workings of Reason
-it is Reason, not the senses,
that defines objects mathematically and deduces logically their properties
-the senses report either
illusions or mere secondary (i.e., accidental) properties of things
-Descartes' epistemology, accordingly, is
called rationalistic rather than empiricistic
-Rationalism vs. Empiricism
-the method of procedure in the
study of nature, then, is to define mathematically the substances at hand and
derive from one's axioms the results (i.e., theorems)
-the axioms will be those found
in mathematics as well as those derived from the metaphysics
-the rules of inference are the
guiding principles of rationality
-inferences in this system are to
be drawn by appeal to the traditional principles of rationality
-The Principle of
Contradiction and
-The Principle of
Sufficient Reason
-The Principle of
Contradiction (also Non-Contradiction, sometimes called the Principle
of Identity) has it's roots in Ancient Greece and has
been used extensively in math as well as the Scholastic philosophy of the
Middle Ages (Anselm, for instance)
-basically, it states that:
(a) what
implies contradiction is necessarily false;
(b) what
opposes contradiction is necessarily true
-it is the basis of all reductio
ad absurdum arguments
-The Principle of
Sufficient Reason also has its roots in Ancient Greece (remember Anaximander?) and is
related to the celebrated Principle of Causality as well as the medieval
dictum: "ex nihilo nihil fit" (out
of nothing comes nothing, or, “nothing comes from nothing”)
-basically, it states that:
-everything has a (good) reason
for being the way it is and not otherwise
-this principle is used in
various forms throughout the modern period
-the two principles are often
combined in a single demonstration and even conflated
-by the time Immanuel Kant (1724-1804) writes
his Critiques, both these principles have undergone important changes
either in content or in domain of application