Transcript Descartes Spring 2011 - University of Arizona

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French philosopher, mathematician and physical
scientist (optics, physics, physiology)
Catholic
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Initially educated at the Jesuit college of La Fleche
Then at the University of Poitiers
Lives in the immediate aftermath of the Protestant
Reformation initiated by Martin Luther (1483-1546)
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Father of Early Modern Rationalist Philosophy
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Early Modern Philosophy is characterized by the thesis
that genuine knowledge can be achieved by humans
through the use of their rational and perceptual faculties
independent of any form of divine revelation.
 A priori knowledge is possible and deploys innate “clear and
distinct ideas”
 A priori knowledge is required in order for there to be a
posteriori, empirical or scientific knowledge.
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Copernicus (Polish; 1473-1543)
 Astronomy: Heliocentric solar system
 Challenge to Church-endorsed Geocentric universe
Francis Bacon (English; 1561-1626)
 Development of the scientific method
Galileo (Italian; 1564-1642)
 Mathematician, Physicist & Astronomer; Copernican
 Challenge to Church’s claims of divine revelation of natural laws
Kepler (German; 1571-1630)
 Discovered laws of planetary motion
Boyle (Irish; 1627-1691)
 Developed experimental chemistry; worked in mechanics, medicine,
hydrodynamics
Newton (English; 1642-1727)
 Fundamental laws of physics; classical mechanics
 Develops the calculus (independently, so too does Leibniz (1646–
1716))
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Descartes is a Foundationalist who repudiates
the Augustinian doctrine of Illumination and
affirms that the human mind is capable of
genuine knowledge of universal and necessary
truths
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Foundationalism: By appropriate use of their
rational faculties for a priori reasoning, humans can
autonomously come to know with appropriate
certainty the fundamental truths evidentially basic
to the empirical or a posteriori sciences of both the
world and ourselves
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As a Foundationalist, Descartes refutes
Skepticism
 The skeptic maintains that
 Certainty is required for knowledge
 However, humans are incapable of
certainty
 Hence, humans are incapable of knowledge
 Thus, science of both the world and
ourselves is impossible
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Meditation I: Descartes’ provisional argument on
behalf of the skeptic
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Knowledge requires certainty.
Certainly is either empirical or a priori
Empirical certainty is impossible because of
 Illusion: hence, no empirical certainty regarding attributes of
material substances
 Hallucination : hence, no certainty regarding the qualities of
of any particular material substance
 Dream Hypothesis: hence, no certainty regarding the
existence of either any particular material substance or
material universe generally
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A priori certainty is impossible because of
 Evil Demon hypothesis
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Hence, certainty is impossible
Hence, knowledge is impossible
Cogito, ergo sum!
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No evil demon could delude one about one’s own
existence
Thus, some a priori knowledge is possible!
Each person can be a priori certain and have genuine
a priori knowledge about
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His/her own individual existence as a thinking substance
The existence and content of his/her own current ideas
(i.e. psychological or mental attributes).
Thus, one can know with a priori certainty what one
believes about
 God
 The material universe.
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Thus, one may know with certainty the content
of one’s idea of God as the perfect being.
Thus, Anselm’s Ontological Argument is certain
and sound.
Hence, God exists!
God’s existence implies that the Demon
Hypothesis is false.
Hence, a priori reasoning can provide certainty.
Hence a priori knowledge of all of logic and
mathematics is possible.
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Perceptual ideas are known reflections
within the mind of the (yet) unknown
character and existence of the external
material
 The existence of God implies that sensation
and perception – if employed according to
God’s design and as characterized by science
- produce generally reliable, even if not
absolutely certain, representations of the
material universe.
 Hence, empirical knowledge of the material
universe is possible through science
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Circularity in arguments for the existence of
God in refuting the Demon Hypothesis
Descartes appeals to the Ontological Argument to
refute the Demon Hypothesis.
 But, the Ontological Argument is an instance of a
priori reasoning.
 All a priori reasoning is dubious according to the
skeptic’s evil demon hypothesis
 So, the Ontological Argument circularly presupposes
that the evil demon hypothesis is false
 In that case, the Ontological Argument is not a
legitimate refutation of the evil demon hypothesis.
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The Cogito aims to demonstrate that we know
with certainty our current thoughts.
But empirical evidence suggests the opposite:
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Evil Sophomores and the effects of psychological
priming:
 I might falsely believe that I am experiencing pain
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The unattended channel and confabulation
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