I. Historical Background and Biographical Information
A. In the 2000 years or so between Aristotle's death and the early 17th
century, with the exception of theology, philosophy remained largely unchanged
- Most people in medieval times were uneducated and poor, life
was centered around the church
- All scholarly works that did exist were written in Latin which
few people spoke
- Certain key religious figures, e.g. St. Thomas Aquinas and
St. Anselm did make substantial contributions to theology, but the
rest of their philosophy was still largely Aristotelian or Platonic
- Much more was being done outside of Europe
B. The 16th century (1500s)
- Called the Renaissance.
- Education became more common and society became more secularized.
- While the Greeks were rediscovered, most advancements were
in art, not philosophy
- Nicolaus Copernicus: (1473-1543): First to suggest that the
Earth revolves around the sun
C. The early 17th century
- Descartes's lifetime
- Often called the beginning of the Age of Reason, or the Enlightenment
, due to people like Descartes himself
- Francis Bacon (1561-1626): wrote about the scientific method
- Johannes Kepler (1571-1630): invented the telescope, did important
work in astronomy
- Galileo Galilei (1564-1642): did work in physics, gravity,
astronomy, especially on proving Copernicus's theories, but was put
on trial by the Church in early 1630's, ended up in house arrest
-- This trial might have had a large effect on Descartes's thought
- Descartes himself (1596-1650)
- After Descartes: Isaac Newton (1642-1727), revolutionized physics;
invented calculus along with Gottfried von Leibniz (1646-1716), who
was also an important philosopher.
D. Descartes' Life
- Born 1596 in La Haye, France (now called "Descartes-La Haye")
- Studied classical mathematics, philosophy and theology at La
Flèche. Really only interested in mathematics.
- Joined the Dutch army, basically became a musketeer
- Had a dream for a new system for the sciences and philosophy
- Left the army, did important work in mathematics and science
(system of optics, Cartesian axis, etc.)
- Finally got around to writing the Meditations in 1640
- In 1649, Taken to Stockholm at the request of Queen Christina
of Sweden, who wanted him to teach her philosophy
- Official story: caught pneumonia, died early the next year
- Unofficial story: got caught up in court intrigue and was assassinated
II. Descartes' Vision for a New Philosophy
A. Wanted a philosophy modeled on mathematics
- All other disciplines full of controversy and uncertainty,
yet no one doubts that 2+2=4
- Admired the axiomatic method of Euclidian geometry, where there
was a small set of fundamental truths from which everything else
- Focus on systematic proofs -- like those you had to
do in high school -- where you started with a set of premises and
carefully proved things using simple deductively valid steps of reasoning.
Try to eliminate any possibility of error.
- Thought this would once and for all allow for precision in
philosophy and for final certainty to be reached
B. Project of the Meditations
- Realized that he previously had believed a lot of false things.
Wanted to "wipe the slate clean", so-to-speak.
- He put it off for so long since it seemed like such a difficult
- Meditation One: "Concerning Those Things That Can Be Called
Into Doubt"-- "At last I will apply myself earnestly and unreservedly
to this general demolition of my opinions."
- If there is any doubt to whether something is true, we must
throw it out. Certainty of the sort possible in mathematics is only
possible by starting with indubitable axioms.
- Once something is thrown out, every belief based upon it would
III. The First Meditation: Descartes's Flight Into Skepticism
Remember that Descartes wants to throw out anything that isn't certain.
So he's looking for something that he can keep -- somethng he cannot
doubt. In the first meditation, he seems to alternate between finding problems
with his beliefs and finding glimmers of hope. But at the end of the first
meditation, the problems win.
First problem: The senses are deceptive. There are optical
illusions and hallucinations that trick our senses. If our senses are deceptive
at all, we can never trust them completely. Therefore, we have to throw out
all sensory knowledge.
First glimmer of hope: But our senses really only deceive
us about small and distant things. Certainly something right in front of
my face that I can perceive with a number of senses cannot be doubted, e.g.,
that I'm sitting here next to the fire. Maybe those things I can still believe.
Second problem: But I might be dreaming! Then I might
perceive something as being right in front of my face and still be mistaken.
Second glimmer of hope: Even if I'm dreaming, I know
that the general kinds of things I experience in my dreams exist.
Even the bizarre monsters I experience are just composed of colors and shapes
that I experience in daily life. This would mean that some sciences might
be mistaken, but that mathematics is still indubitable. After all, the mathematics
of triangles doesn't depend on the existence of any particular
triangles anywhere... only on the essence of triangles in general.
Third problem: But God is all powerful. God could make
it so that I think there is a physical world and things corresponding to
the general sorts of objects I experience when there is not. In fact, God
could even deceive about the truth of mathematics. Therefore, even these
things can be doubted.
Third Glimmer of Hope: But God is supposed to be supremely
Good. He would not deceive me, at least not all the time.
Fourth problem: But God might not exist at all. That
would only make me less sure that I might not be deceived. What
is worse is that instead of God, there might exist an evil genius who does
everything he can do deceive me. All my experiences are mere illusions. There
is no earth or heavens. I have no body. He makes me think false things about
mathematics. In short, he deceives me about everything.
Conclusion of the First Meditation: Descartes has now
been reduced to total skepticism. The possibility of an evil genius existing
instead of God makes him doubt everything. He has yet to find anything which
meets his criteria for knowledge. He gives up for the night, concluding at
least that he will spite the evil demon by at least refusing the believe
the false things he used to believe.
IV. The Cogito: Descartes'
Fundamental Principle (Meditation II)
A. The night before Descartes was lead to utter skepticism, and is now
certain only that nothing seems certain.But he has hope that if could find
just one indubitable truth to cling to, he might use it as a starting place
to discover more. So he starts looking for one. He had assumed that God or
an evil genius was the cause of his false experiences. So he asks whether
then God or the evil genius must exist in order to cause the illusions. But
he concludes that it might be he himself who somehow tricks himself. But
then he asks whether then he himself must be something, which leads him to
his great discovery.
B. Descartes's famous saying "Cogito ergo sum." (Latin), "Je pense, donc
je suis" (French) or "I think, therefore I am." (from the Discourse on
- That "I exist" must be true every time I think it
- It's impossible for me to doubt that I think. It's just incoherent
to say "I think I don't think." So I know I'm thinking, and if I'm
thinking, there must be a "me" to do the thinking
- This one fundamental principle ("The cogito") can
serve as a foundation upon which to arrive at truth
C. But what am I? I know I exist. What is my essence
- I used to think I was a "rational animal" or a being with a
body that walks around and eats
- But all of this are uncertain. I might not be those things,
but even then I would still be me. They cannot be part of my
- I know I exist so long as I am thinking. What am I then, fundamentally?
I am a thinking thing (res cogitans).
- I am a mind, something that doubts, understands, affirms,
wills, refuses, and also imagines and senses.
- Senses? How can the "mind" sense? Don't sense organs "sense"?
If the mind senses, then sensing must be a kind of thinking. Descartes
admits this. I might not have any sense organs and all my sense
perceptions might be false, but I can't be wrong that I at
least seem to see things, that certain images are present
in my mind. I can't be wrong about whether or not I have
those images, only about whether they represent things outside me.
So,.yes, they are like thoughts. And yes, they exist within the mind
and not in the sense organs. Sense organs might not even exist!
V. The Wax: Rationalism and Substance
A. At this point, Descartes stops and thinks it's strange that the mysterious
self or "I" should be better known and more certain than the things we see
and feel every day. How can this be?
B. He decides to take the piece of wax as an example and considers it.
What do we know about it, and importantly, how?
- By my senses, I see the color and shape of the wax, I smell
its fragrance, I feel its hardness, I hear a noise when I tap it.
- But if I bring the wax close to the fire and it melts, what
changes? It's not the same color, shape or size. It doesn't smell
the same. It is no longer hard and no longer makes a noise when tapped.
- Now the wax still exists, but none of the attributes
it had which I perceived by the senses are the same.
- Descartes' conclusion: The senses only allow us to know the
accidental properties of the wax. The wax itself--the thing that
exists throughout the changes--the wax as substance, is
not something I know by senses. Rather, I know it by my mind or intellect.
C. What does all this mean? Everything we see and touch is most directly
grasped by the mind. The mind is needed to perceive anything. So it really
isn't so strange that the mind should be better known than ordinary physical
D. Of course, I might be wrong. My intellect may be in error. Maybe there
is no wax itself, no substance "out there". But that just goes to reiterate
that my mind must exist, for even if I am in error, it is me or
my mind that is in error.
E. The conclusion: There is nothing better known to me than my mind
. Certainly not my body or my sense organs or the attributes perceived by
VI. The Ontological Argument for the Existence
A. What we skipped
- Meditation III: Descartes's first proof
- Meditation IV: A discussion about whether
God could be a deceiver and what is necessary in order to avoid making
errors on one's own
B. First of all, why does Descartes want
to prove the existence of God at this point?
- The possibility that he is controlled
by an evil genius still keeps him from being sure of anything
-- the physical world, mathematics
- Even the cogito is uncertain for this reason -- the
evil genius might be tricking me (me?) about what seems like the
clearest and distinct and most indubitable truths, even about logic
- But if God existed, then since we know God is supremely good,
we know that God would not deceive us about the things that we clearly
and distinctly perceive or have concluded to be true by careful
use of reason
- So we'd better prove that God exists, otherwise we'll always
have lingering doubts
C. The Existence / Essence distinction revisted
- Descartes here talks about the idea of a triangle
- Even if there are no triangles "out there in the world", or
in Aristotle's term, there are existing traingular substances,
there still is an essence or form of triangles
- We can still deduce geometric truths about triangles just based
on their essence or their definition. These things about the essence
of a triangle would be true even if no triangles existed "out there".
After all, we can deduce all sorts of truths about shapes which we've
never seen in nature and probably don't exist anywhere in
nature. (i.e. a 127 sided figure). The mathematics is still true.
D. The proof of the existence of God
- Roughly the same as St. Anselm's (1033-1109) "Ontological Argument"
from the Proslogion
- Descartes has an idea of God. God's essence is being a supremely
- What's different is that this makes God's existence inseparable
from his essence. A supremely perfect being must have all
perfections, and something that doesn't exist lacks the perfection
- It is as contradictory to think of God without existence as
it is to think of a mountain without a valley or a triangle without
- It might seem at first that we can imagine God as not existing
or separate his existence from his essence, but not if we think more
about God's essence. We might also at first think that there are
right triangles which do not follow the Pythagorean theorem, but
if we think about it, we will recognize that this is impossible.
E. Now that God has been proven to exist, Descartes can breathe a sigh
of relief. Now, since God is not a deceiver, he can trust any perception
he has which is clear and distinct, and he can trust his reasoning about
mathematics, etc. There is no evil genius.
1. Problems with the ontological argument
- What is a "supremely perfect being"? Does this make any sense?
- Why is existence a perfection?
- Can we really define things into existence? Personal ad example.
Perfect island example.
2. "The Cartesian Circle"
- Descartes wanted to prove that God exists so that he could
trust his reasoning
- However, Descartes used reasoning to prove the existence of
- If the evil genius was truly able to deceive him even about
logic itself. then the evil genius could have tricked him about his
proof for the existence of God.
- So Descartes's solution to the evil genius problem is circular.
He uses reasoning to try to justify his reasoning as sound.
- Did he really have any other options?
VII. The End of Descartes' Skepticism and the Arguments for Dualism
A. Descartes has proven that whatever he clearly and distinctly perceives
is true. This means
- While the senses are not to always be trusted, when they are
used properly and the ideas that they furnish are clear and distinct
enough, they can be a source of knowledge
- In general we can conclude that there are things out there
that resemble the ideas we have from sense -- sky, earth, sea
- I also know that there is one physical thing in particular
-- the body, which bears a special relation to me as a thinking thing.
I cannot be separated from it. I feel certain desires and sensations,
pains and hungers and excitements "on its behalf"
B. And in general, if two things are clearly and distinctly perceived
to have different natures, they are different substances. This is true of
the mind and the body.
- The essence of the mind is that of a thinking thing
which is not extended, corporeal or divisible.
- The essence of the body is to be extended, corporeal and divisible.
- As we've seen, one can be known to exist without the other.
Therefore, it is possible that they could actually exist independent
of one another; hence, they are different substances.
- Still, there is a connection between them. The activities of
the brain are especially correlated with the activities of the mind
(although they are surely not the same thing!)
- Nerves in our body connect to our brain and when they are "pulled",
not only do they cause motion in the brain, but also a sensation
in the mind
- Similarly, certain acts of the mind (acts of willing) bring
about "swerves" in the mechanics of the body
- This area of Descartes's thought is rather puzzling: How it
possible for something immaterial to cause motion in the material
world and vice-versa? Descartes doesn't tell us, but suggests it
has something to do with the pineal gland.. This is not very helpful.
"The problem of mind-brain interaction."
C. Finally, Desartes rids himself of the doubts considering whether he's
dreaming. The images of dreams are not clear and distinct like regular experiences.
Instead, they involve people appearing and disappearing, no continuity, etc.
So my dream experiences are not to be trusted, but my regular experiences,
which are not like this, are trustworthy.
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