DESCARTES
MEDITATION ONE
PHIL 100, INTRO TO PHILOSOPHY
SUMMER 2011
BENJAMIN VISSCHER HOLE IV
OUTLINE
1. Context, Preliminaries and Terminology
2. Method of Doubt
3. The Insanity Argument
4. Argument from Illusion
5. The Dreaming Argument
6. The Brain-in-a-vat Argument
7. The Evil Deceiver Argument
CONTEXT
• Francis Bacon (1561-1626)
• Johannes Kepler (1571-1630)
• Galileo Galilei (1564-1642)
Rene Descartes (1596-1650)
• Studied classical mathematics,
philosophy and theology.
• Considered to be the father of modern
philosophy ... Or, at least epistemology.
EPISTEMOLOGY
• What is knowledge?
• What can you know?
• What are the limitations of your
knowledge?
• What are the best methodologies for
justifying the things you believe?
SKEPTICISM
“The view that knowledge is unattainable.
One can be a skeptic about knowledge
generally or some limited domain” (650)
Academic vs. Pyrrhonian
WHAT DO YOU
KNOW?
Knowing how vs. Knowing that
• Knowing how to ride a bike, make lasagna, etc.
• Knowing that 2+2=4, water is H2O, grass is green, etc.
• According to intellectualists: either knowing how to do
something is a matter of knowing that something is the case
or, at the very least, know-how requires a prior bit of
theoretical knowledge.
• Anti-intellectualists deny this order of priority: either
knowing-how and knowing-that are independent or, at the
very least, knowing that something is the case requires a prior
bit of know-how.
Jeremy Fantl, Knowing-How and Knowing-That, Philosophy Compass, 451–470, May 2008.
KNOWLEDGE = JTB
TERMINOLOGY
Necessity (Logical): X
on all possible worlds.
Contingency (Logical):
X on at least one, but
not all, possible worlds.
Logical Possibility: X on at least one
possible world.
TERMINOLOGY
“analytic/synthetic A distinction
concerning the logical structure of a
proposition” (636).
“a priori/a posteriori This is a distinction
concerning the reasons or justification
offered for a claim” (637).
DISCUSSION POINTS
Is it possible to have …
1.A contingent truth knowable a priori?
2.A necessary truth knowable a posteriori?
3.A necessary synthetic truth knowable a priori?
Key Distinctions
Necessary / Contingent
A Priori / A Posteriori
Analytic / Synthetic
DESCARTES
•Rationalism: knowledge is possible
through the intellect/reason …
•Motivated to defeat skepticism …
•… And to provide a foundation for his
philosophy.
METHOD OF DOUBT
“doubt anything that can possibly be false, thereby arriving
(if anything is left) at certainty. Notice he is not seeking
merely psychological certainty … Instead he is looking for a
kind of certainty that guarantees truth: beliefs for which there
is a conclusive reason” (47).
METHOD OF DOUBT
“And thus I realized that
once in my life I had to
raze everything to the
ground and begin again
from the original
foundations, if I wanted to
establish anything firm and
lasting in the sciences. But
the task seemed enormous
…” (47).
1. Never accept any belief as true
without conclusive justification of
its truth.
2. A logical possibility is reason
enough for doubt …
3. Divide complex ideas into simpler
parts.
4. The best methodology is bottomup; find simple indubitable ideas
and build up from there.
THE FIRST PROBLEM
Our senses are imperfect …
“However, I have noticed
that the senses are
sometimes deceptive; and it
is a mark of prudence never
to place our complete trust
in those who have deceived
us even once” (48).
ARGUMENT FROM
ILLUSION
1. Sensible objects do not vary
with perspectival variation.
2. My sense perceptions of
sensible objections vary with
perspectival variation.
3. Therefore, I do not
immediately perceive the
senses.
“An argument for the view that what we are directly or immediately aware of
in normal cases of sense perception is not an externally existing material
object, but instead something like an idea or sense datum” (637).
ARGUMENT FROM
ILLUSION
1. When viewing a straight stick half-submerged in water, one is
directly aware of something bent.
2. No relevant physical thing is bent in this situation.
3. Therefore, in this situation, one is directly aware of something
non-physical.
4. What one is directly aware of in this situation is the same kind
of thing that one is directly aware of in normal, non-illusory
perception.
5. Therefore, in normal perception, one is directly aware of nonphysical things.
From SEP: http://plato.stanford.edu/entries/sense-data/#ArgIll
INSANITY ARGUMENT
“Unless perhaps I were to
liken myself to the insane,
whose brains are impaired by
such an unrelenting vapor of
black bile that they
steadfastly insist that they
are kings when they are utter
paupers, or that they are
arrayed in purple robes when
they are naked, or they have
heads of clay, or that they are
made of gourds, or that they
are made of glass” (48).
SKEPTICAL
ARGUMENT
1. A skeptical hypothesis is
possible.
2. If the skeptical
hypothesis is possible,
then I cannot rule out
that it is actual. (Method
of Doubt.)
3. If I cannot rule out that it
is not actual, then my x
beliefs are dubitable.
INSANITY
ARGUMENT
1. It is possible that I am
insane … in which case,
all of my beliefs are
dubitable.
2. If it is possible that I am
insane is possible, then I
cannot rule out that it is
actual. (Method of
Doubt.)
3. Since I cannot rule out
that it is not actual, all of
my beliefs are dubitable.
GLIMMER OF HOPE?
Senses are usually reliable
“But one what grounds could
one deny that these hands
and this body are mine?” (48)
I don’t feel crazy …
“I would appear no less mad,
were I to take their [insane
people] behavior as an
example for myself” (48).
THE DREAMING
ARGUMENT
“This would all be well and good, were I not a man who is
accustomed to sleeping at night, and to experiencing in
my dreams the very same things, or now and then even
less plausible ones, as these insane people do when they
are awake” (48).
THE DREAMING
ARGUMENT
1.
Sensory experiences we have
in dreams produce false
beliefs about what is in our
immediate environment.
2.
For any given waking
experience that experience
could be dreamed.
3.
There is no way of knowing if
any given sensory experience
is waking or dreaming.
4.
Therefore, there is no way of
knowing whether the
experience I am having right
now is producing a false
belief.
THE DREAMING
ARGUMENT
1.
Sensory experiences we have
in dreams produce false
beliefs about what is in our
immediate environment.
2.
For any given waking
experience that experience
could be dreamed.
3.
There is no way of knowing if
any given sensory experience
is waking or dreaming.
4.
Therefore, there is no way of
knowing whether the
experience I am having right
now is producing a false
belief.
Discussion Points
1.What kind of knowledge does
the dreaming argument call into
doubt? How problematic is this in
general?
2.Is the dreaming argument a
priori or a posteriori? Are there any
places where Descartes is
unclear?
A CONTEMPORARY
ANALOGUE
BRAIN-IN-A-VAT
ARGUMENT
You might be a BIV!
Everything you
experience is virtual
reality. Your sense
perceptions aren’t
caused by boats or
people or whatever,
they’re caused by some
computer.
BRAIN-IN-A-VAT
ARGUMENT
1. If I can’t rule out the
brain-in-a vat scenario,
then I can’t know what
my present situation is.
2. I can’t rule out the
brain-in-a-vat scenario.
3. I can’t know what my
present situation is.
ARGUMENTATION
Drop my MoTo on your MoPo!
MODUS PONENS
MODUS TOLLENS
1. If A, then B.
1.If A, then B
2. A
2.Not B
/.: B
/.: Not A
G.E. MOORE’S SHIFT
1. If I can’t rule out the
brain-in-a vat scenario,
then I can’t know what
my present situation is.
2. I do know what my
present situation is.
3. I can rule out the brainin-a-vat scenario.
BIV VS. MOORE’S SHIFT
•
Both arguments are valid.
•
To determine which argument we should believe, we have
to determine which argument is sound.
•
Both arguments have the same 1st premise.
1. If I can’t rule out the brain-in-a vat scenario, then I can’t know
what my present situation is.
•
So, which premise 2 is should we accept—that of BIV
Argument or Moore’s Shift?
BIV AND THE G.E.
MOORE SHIFT
BIV ARGUMENT
MOORE’S SHIFT
1.
If I can’t rule out the
brain-in-a vat
scenario, then I can’t
know what my
present situation is.
1.
If I can’t rule out the
brain-in-a vat
scenario, then I can’t
know what my
present situation is.
2.
I can’t rule out the
brain-in-a-vat
scenario.
2.
I do know what my
present situation is.
3.
I can’t know what
my present situation
is.
3.
I can rule out the
brain-in-a-vat
scenario.
THE DREAMING
ARGUMENT
1.
Sensory experiences we have
in dreams produce false
beliefs about what is in our
immediate environment.
2.
For any given waking
experience that experience
could be dreamed.
3.
There is no way of knowing if
any given sensory experience
is waking or dreaming.
4.
Therefore, there is no way of
knowing whether the
experience I am having right
now is producing a false
belief.
GLIMMER OF HOPE?
The dreaming argument only
applies to a posteriori
knowledge …
“Thus, it is not improper to
conclude from this that
physics, astronomy, medicine,
and all the other disciplines
that are dependent upon the
consideration of composite
things are doubtful, and that,
on the other hand, arithmetic,
geometry and other such
disciplines” (48).
COULD GOD DECEIVE
US?
God is all powerful …
God is all knowing …
God is all good …
EVIL DECEIVER
ARGUMENT
God may not exist
at all …
Perhaps I am
being deceived by
an evil demon …
Let’s call him ED.
EVIL DECEIVER
ARGUMENT
1. ED is possible.
2. If ED is possible, I
cannot rule out
that he is not
actual.
3. If I cannot rule out
that he is not
actual, then my
beliefs of reason
are dubitable.
EVIL DECEIVER
ARGUMENT
Objections?
1. ED is possible.
2. If ED is possible, I
cannot rule out
that he is not
actual.
3. If I cannot rule out
that he is not
actual, then my
beliefs of reason
are dubitable.
SUMMARY OF
MEDITATION ONE
1. Knowledge is either a priori or it is
a posteriori.
2. If it is a posteriori, we do not have
it (because of the dreaming
argument).
3. If it is a priori, we still do not have
it (because of the evil deceiver
argument).
4. Therefore, we do not have
knowledge.
WE DON’T KNOW ANYTHING!