Lone Star College Descartes Project Brief Explanation 1. Provide a brief explanation of the project Descartes set for himself and why he undertook it2. Next, briefly outline his path to the cogito and beyond (his starting point, his arguments, why the cogito was so important to him, his proof that the world exists)3. Finally, briefly explain the Cartesian circle, and why Descartes matters anyway Descartes’ Legacy
Descartes’ arguments shaped
thought for the next several
centuries, despite flaws that were
perceived almost immediately
Specific Learning Objectives
• Learning outcome:
– Be able to explain the circularity in Descartes’
reasoning, and assess Descartes’ legacy
• Learning objectives:
1. Explain what is meant by the Cartesian circle
2. Discuss the influence of Descartes’ work
Descartes’ Clear And Distinct Rule
• Remember the rule:
Guiding
Rule
– “I now seem to be able to lay it down
as a general rule that whatever I
perceive very clearly and distinctly is true.”
• Descartes adopted this rule because it
seemed to apply in three cases
1. That he himself exists (his cogito argument)
2. That as himself, he is a “thinking thing”
3. That he can be certain of the current contents of
his conscious mind
Descartes’ Clear And Distinct Rule
• In all of these cases he felt compelled to
believe because of his clear and distinct
perception they were true
• And since God is perfectly good (and
omnipotent and omniscient), he would not
build us in a way that we
are compelled to believe
something that is not true;
“God is not a deceiver”
Descartes’ Proof Of God
• But Descartes has already used the clear and
distinct rule in his argument to prove the
existence of God
1. He has a clear and distinct idea of God as a
supremely perfect being
2. Therefore God is a supremely perfect being
3. God would not be supremely perfect if he did
not exist
4. Therefore a supremely perfect God exists
The Cartesian Circle
• So it looks like Descartes is arguing in a circle
– He invokes the clear and distinct
rule in his argument for
God’s existence
– But he invokes God’s
existence to argue that the
clear and distinct rule is is correct
• This is known as “the Cartesian Circle”
– Since circular arguments assume what they are
trying to prove, they are unconvincing
The Cartesian Circle
• If there really is an evil demon, our “clear and
distinct perceptions” could also be wrong
– We might well feel compelled to believe
something that turns out to be completely untrue
• So Descartes has not succeeded
in ruling out the possibility that
we are being deceived by an Evil
Demon—or the possibility that
almost all our beliefs are false!
The Cartesian Circle
• This objection was raised during Descartes’
own time, to which had several responses
– Most important: he points to the cogito as not
depending on a guarantee from God, but as selfverifying: if I doubt, then I must exist
• Not all contemporary philosophers accept
that Descartes’ reasoning was circular
– Much depends on close analysis of Descartes’ own
words, in the texts and his letters to critics
Impact on Descartes’ Legacy
• Despite the largely accepted conclusion that
Descartes’ reasoning was flawed, his work
has had a long and powerful influence
• It is easy to think of him now as just a figure
in history, but he played a
seminal role in transforming
our world from one driven
by religious doctrine to one
driven by the power of
human reason
Descartes The Revolutionary
• Descartes died at the age of 53, and we can
only speculate about what he might have
accomplished had he lived longer
• The revolutionary nature of his thinking was
not lost on the Church
– After his death, the Church places his works were
on the list of banned books
• However they had already gained wide distribution and
were being widely read
– For centuries, truth had been determined by the
Church fathers; Descartes had the audacity to ask
“what is certain?”
Descartes The Independent
• He transitioned philosophy away from
Church doctrine to independent investigation
– It’s important to understand how transformative
Descartes was for his contemporaries
– He insisted on thinking for ourselves rather than
accepting dogma from authority figures
• He re-introduced a style of thinking that has
been widely used ever since
– St. Augustine is considered to have been first to
use the first person approach to thinking
philosophically a thousand years before
Descartes The Methodical
• His systematic and methodical approach
provided a blueprint for laying out a clear line
of reasoning, challenging every premise at
every turn
– Not to prove his premises right, but
to attempt to find out in which way
they were wrong
– Only by figuring out what’s wrong
with what we believe can we make
progress toward an improved understanding
Descartes The Rational Skeptic
• He pushed skepticism to its limits, doubting
even his own existence, but didn’t stay there
• Instead he moved from radical skepticism,
which corrodes all that it touches, to a useful
skepticism, to be used as a tool
– We are justified in believing in our ability to
reason, and in our perceptions and memories, as
long as we are willing to subject them to scrutiny
• This point will be important when we take a look at the
British empiricists in the next chapter
Descartes The Philosopher
• Descartes’ works were widely discussed, and
influenced philosophical debate ever since
– His mind-body and subject-object dualism
• Ever since Descartes, the relationship between our
inner world (conscious awareness) and our outer world
(beyond conscious experience) has been a hot debate
– His emphasis on subjective experience
• Influenced later existentialist philosophers
• Dreaming, hallucinating, feeling pain and being
conscious of having experiences have since then
become philosophical problems of their own
Descartes The Philosopher
• Not as widely discussed but also very
influential
– His writings on human emotions and ethics
• Though a rationalist, Descartes also wrote extensively
on human emotion, and on why the truly virtuous
person seeks spiritual rather than sensual pleasures
– His mechanistic view of the nature of animals
• Descartes argued that unlike humans, animals did not
have the capacity for reason
• This had the unfortunate effect of granting humans
license to mistreat animals for centuries
Descartes The Scientist
• He also made a number of important
contributions in the sciences
– He invented analytic geometry, which paved the
way for calculus and made possible many
advances in physics
– His methodical approach shaped what would
become a general scientific method
– His work in optics contributed to the design of
optical instruments (such as telescopes)
– His detailed study of rainbows was later finalized
by Newton in his study of the nature of light
Descartes’ Cultural Legacy
• It is ironic that while Descartes set out to
achieve certainty, he is perhaps remembered
most for an argument that seems to show
that there is very little of which we can be
certain: the evil genius
– An evil demon or genius will pop up
in many thought experiments in the
centuries to come, in philosophy
and in literature
– Most recently: The Matrix movies
Scientific American, April 7, 2016
https://www.scientificamerican.com/article/are-we-living-in-a-computer-simulation/
Learning Objective REVIEW
• Check your understanding of the Cartesian
circle and the legacy of René Descartes
1. Explain what is meant by the Cartesian circle
2. Discuss the influence of Descartes’ work
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