Rene Descartes--(1596-1650)
French philosopher who is many ways is the founder of modern day
epistemology.
Most famous works, Discourse on Method, The Meditations,
Geometry,
and On
the
Passions of the Soul.
Some Terminological Clarifications
foundationalism--The view
that all propositions we know to be true can be divided into
two categories.
First, there are foundational propositions, which have some special
property
(like indubitability) that explains why we know them to be true. Second,
there
are super
structural propositions, which we know because they bear a special relationship
(like
deductive implication) to foundational propositions. (Sober 572)
skepticism--The thesis that
knowledge (or rational justification) is unobtainable. Descartes tried
to refute
skepticism about knowledge; Hume was a skeptic about the rational justifiability
of induction.
(Sober 575)
a priori--A proposition that
can be known or justified independent of experience, once the concepts
are grasped.
These are justified by reason alone. For example, a triangle has three
sides. (569)
a posteriori--A proposition
that can be known or justified only through our sense experience.
For example,
"The CLA building is 205 feet tall." "I have a maroon colored car." (569)
indubitable--something that
cannot be doubted except on the pain of contradiction or inconsistency.
For example,
I cannot doubt a triangle has three sides; because if I think of it another
way, such
as having
four sides, I've contradicted myself. Notice however, this is a logical
property. What this
means
is that doubting a belief consists of being able to construct a story that
calls into question
the truthfulness
of a belief. The story need not actually exist or hold, but since you can
construct
such
a story, you have set the belief into a logical relation with other beliefs,
and thus, indubitability
is a
logical property.
axiomatic method--find axioms
(things that are not proven but known to be true) and derive theorems
(things
proven from axioms and can then be used to prove other things) from them.
You do this all
through
a process of rational intuition, the mental act of understanding
the truth of self-evident
indubitable
axioms. (Wall 147)
Axioms
------------------------------
Theorems
+
Axioms/Theorems
-----------------------------
Theorems
If you notice, the above
structure is an example of foundationalism. Axioms are certain and we
have a structure to guarantee
their certainty. Why is this important? If we can all agree on the
axioms, we can agree on
what follows from them, and we will agree on what knowledge
or what we can know consists
of.
---------
The Meditations
General Idea
Descartes
wants to find something indubitable to base his theory of knowledge upon.
To get to
indubitability,
Descartes initially proceeds through a method of doubt. If you can doubt
a belief,
it is
not foundational or not indubitable. He then tries to doubt everything,
but this needs to be
qualified.
He cannot doubt every single belief, so he doubts types of beliefs. He
doubts
a
posteriori beliefs and concludes the senses can deceive us. He also,
surprisingly,
doubts
a
priori beliefs given the right story. He arrives at something that
he believes
cannot
be doubted, that he is thinking and a thinking thing. From there he builds
his foundation
up and
begins reconstructing his world and what can be known. So, very generally,
he goes
through
a method of doubting types of things, finds something he cannot doubt,
and then
reconstructs
his world and what he knows. His ultimate goal is certainty about knowledge.
Against Skepticism
Descartes
is arguing against the following argument and ultimately wants to answer
why it
fails:
General
Skeptical Argument
P1--Knowledge
requires the impossibility of error or being wrong.
P2--It
is possible right now that I am wrong in believing that there is a classroom
full of students
in front of me.
-------------------------------------------------------------------------------------------------------------------------
C--Thus,
I don't know there is a classroom full of students in front of me.
A VERY
IMPORTANT POINT--Descartes is arguing against epistemological skepticism
or the belief
that
knowledge is unobtainable. However, he uses a form of skepticism called
"methodological
skepticism."
The method of doubt is a skepticism about how one proceeds or acts and
it is for
a purpose.
In other words, you can apply the method of doubt as a way of getting to
a conclusion
you want
without being a skeptic. He is using skepticism to prove a point. This
is exactly what
Descartes
does.
An analogy.
Suppose the pipes under my sink go bad and are leaking. I decide to fix
them.
I can
buy all of the tools needed to fix the sink, along with the parts. I do
it. Does that make
me a
plumber? No, while I may use the same tools and parts to fix the problem,
I don't share
their
overall knowledge or outlook on the matter. Descartes is using skepticism
much like
I used
the tools and parts.
General Argument Against Skepticism (from Wall, p148)
P1--Philosophical
knowledge is like mathematical knowledge.
P2--Mathematics
is based upon indubitable axioms.
------------------------------------------------------------------------------------------------
C--Therefore,
philosophy is based on indubitable axioms.
If this
argument is true, we defeat P1 in the skeptical argument because of the
characters of
foundationalism
and indubitability.
Argument Against A Posteriori Knowledge (The Dream Argument)--Wall, p. 150
P1-If
dream states cannot be distinguished from waking states, then dreams cannot
be
distinguished from reality.
P2-Dream
states cannot distinguished from waking states.
---------------------------------------------------------------------------------------------------------------------------------------
C--Therefore
dreams cannot be distinguished from reality and truths of this type--a
posteriori.
Notice
the internalism here. Representations are caused by the mind, and the mind
represents
the world and dreams in the same way.
Argument Against A Priori Knowledge (The Evil Genius)
P1--An
Evil Genius exists who can cause me to doubt everything I know to be true.
P2--2
+ 2 = 4 is something I know to be true
P3--2
+ 2 =4 is not really true because the Evil Genius has deceived me.
P4--The
Evil Genius has deceived me of every truth of this type--a priori (and
a posteriori).
------------------------------------------------------------------------------------------------------------------------------
C--All
truths, including a priori, are false.
At this point, Descartes
has doubted everything that he can and is ready to reconstruct his system.
What is the one thing that
he can't doubt? That he is a thinking thing and that he exists. Why is
the
this indubitable? On the
pain of contradiction, if you assert you don't exist, you are asserting
you
exist. This is known as
a performative contradiction. For example, if I say out loud, "I cannot
say
a word in English" I have
contradicted myself because the very thing I said I could not do, I did
in the act of denying it.
From the Discourse on Method,
Descartes says, "I noticed that while I was trying to think everything
false, it must be that
I, who was thinking this, was something. And observing that this truth,
I
am
thinking, therefore
I exist, was so solid and secure that the most extravagant suppositions
of the
skeptics could not overthrow
it, I judged that I need not to scruple to accept it as the first principle
of the philosophy I was
seeking."
We have our first axiom then: A1--I am a thinking substance and I exist.
A1 is an analytic claim for Descartes. You may want to look at it like: I am thinking = I exist.
The question is, what does
the "I" refer to in A1? It refers to the mind or soul. Wall provides
an argument
on why the mind is not the body for Descartes. The body can still be doubted
due to
the Evil Genius.
P1--If
I exist and my body may not exist, then I am not my body.
P2--I
exist.
P3--My
body may not exist.
--------------------------------------------------------------------------------------------------
C--Therefore,
I am not my body.
Wall's
argument trades upon noticing how 'exist' is used and Descartes' mind/matter
dualism.
In the
first case, the "I" existing refers to the mind or non-physical substance,
and in the second
case
of "..my body..." refers to the physical substance. Descartes referred
to these two
substances
in the following way and I think his reference is quite helpful. The thinking
substance
was called
'res cogitans' and the material/physical substance as 'res extensa.' The
difference is
the following:
res cogitans means thinking and not extended in space, where as res
extensa
means
extended in space and things extended in space have physical properties.
A Qualifier
Built
into Descartes project is the notion of psychological incorrigibility or
that you have infallible
access to what you believe and desire. This is a hard point to grasp in
many ways. If I say,
"There are students sitting in front of me" I can doubt that proposition
given the either the
Dream or the Evil Genius argument. But, if i say, "I believe that there
are students sitting in
front of me" I cannot doubt that because if I believe that I have a belief,
then it must be true
that I have the belief.
Wall puts its very well, "Still, while no one else can correct my reports
about my own mental
states, it is an assumption for Descartes to believe that whatever is going
on in the theater of
his mind is known by the mind itself and known with certainty." As you
can see this is a very
strong form of rationalism, what is going on in the mind guarantees that
it is known and is
certain. Going back to the previous example then, we see that having the
belief that students
are sitting in front of me is an operation of the mind and guaranteed by
the mind. Descartes
wants to include all beliefs of this type as foundational as well. These
beliefs must meet two
criterion: they must be clear and they must be distinct, and
if a belief meets these two criterion,
it mustbe true.
So to
this point we have that we are thinking things and we can't think wrong
about things if they
are known and guaranteed by the mind or the thinking substance. Notice
that the thinking
substance comes in here as a guarantee of reliability of beliefs, or our
beliefs are reliable
because of the thinking substance. This is only partly true because Descartes
ends up using
God as a guarantee as well.
Other Axioms
A2--God is a perfect being.
He gets to the conclusion
with his own form of a causal argument, from (Sober 166).
P1--My idea of God is an idea of a perfect Being.
P2--There must be at least as much perfection in the cause, as in the effect.
----------------------------------------------------------------------------------------------------------------------
C-Hence the cause of my idea of a perfect being is God himself.
Alternatively,
P1--My idea of God is objectively perfect.
P2--If an idea is objectively perfect, then the cause of that idea must
be
perfect.
--------------------
C--Hence, God exists.
A3--God exists and he is no deceiver.
Descartes
reaches this conclusion because if God gave us a mind that allowed us to
reason,
and if we reasoned carefully, and still reached false beliefs based upon
reason and
evidence, God would be a deceiver. Since God is perfect, he is no deceiver.
What this
axiom also guarantees is that we have a link between our beliefs about
the world
and the world itself. If a belief is not foundational, it can be
in error. However, we have the
capacity to have all true beliefs if we use the minds that God gave us
but it is not likely.
Wall formulates this like the following:
P1--If God is a perfect being, then God cannot deceive. A--->B
P2--God is a perfect being.
A
----------------------------------------------------------------------------------------------------
C1--Therefore, God cannot deceive
B
P3--If the world does not exist, then God deceives.
~A---->B
P4--God cannot deceive
~B
----------------------------------------------------------------------------------------------------
C2--Therefore the world exists.
~~A = A
A4--The world exists.
-----------------------------------------------------------------------------------------------------------------------------------------------------
Summary of the Axioms to this Point
A1--I am a thinking substance
and I exist.
A2--God is a perfect being.
A3--God exists and he is
no deceiver.
A4--The world exists.
Since axioms must meet the
clearness and distinctness criteria, they are all true for Descartes.
We might ask, what guarantees
the "clearness and distinctness criteria" that ideas actually are
'clear' and 'distinct'?
P1--God is not a deceiver.
P2--If ideas were not 'clear'
and 'distinct' that would require deception.
------------------------------------------------------------------------------------------------------------
C--God not being a deceiver
guarantees that some ideas are "clear and distinct."
We might then ask, what guarantees
that we know God as a perfect being?
It is the clearness and
distinctness criteria.
This is commonly known as the Cartesian Circle.
God guarantees that we have
clear and distinct ideas, and clear and distinct ideas
guarantee that we have God
in some sense.
Conclusion
Remember the General Skeptical Argument from Sober,
General Skeptical Argument
P1--Knowledge
requires the impossibility of error or being wrong.
P2--It
is possible right now that I am wrong in believing that there are a classroom
full of
students in front of me.
-------------------------------------------------------------------------------------------------------------------------
CS--Thus,
I don't know that there is a classroom full of students in front of me.
Descartes is going to contest
P2 here. Remember the bit about first-person beliefs being
incorrigible?
He can't be wrong about believing if he/she has taken the time to reason
in
a careful and logically rigorous manner.
Descartes Response to
the Skeptical Argument from Sober,
P1--If
God exists and He is no deceiver and I now have a clear and distinct belief
that
there is a classroom full of students in front of me, then I can't be mistaken
in thinking
that there is a classroom full of students in front of me.
P2--God
exists and is no deceiver and I now have a clear and distinct belief that
there is a
page in front of me.
-------------------------------------------------------------------------------------------------------------------------------------------
CD--I
can't be mistaken in thinking that there is a classroom full of students
in front of me.
Remembering back to the earlier claim, Wall will contest P1 of the General Skeptical Argument.
General Argument
Against Skepticism (from Wall, p148)
P1--Philosophical
knowledge is like mathematical knowledge.
P2--Mathematics
is based upon indubitable axioms.
------------------------------------------------------------------------------------------------
C--Therefore,
philosophy is based on indubitable axioms.
We have the axioms that Descartes
thought were indubitable and he based his philosophy on
them
as foundational.
If you take these two arguments,
Descartes Response and General Argument Against Skepticism,
seriously
both of the skeptics premises have been defeated and the Cartesian project
is
successful.
Ultimately, God does a lot
of work in Descartes system. If the arguments for his existence don't
work,
then the guarantees do not hold. To see this take God out of his axioms,
you don't
have
the reliability of clear and distinct ideas, nor the guarantee that there
is even an
external
world. Both P1 and P2 of the General Skeptical Argument appear to hold
without
God in
the picture because beliefs can be doubted and one can be wrong about their
beliefs
and knowledge. I think God functions as an explanation for Descartes and
does
too much
work for him. The Cartesian Project is interesting though if you buy the
axioms.
Questions to consider:
1) What is foundationalism in epistemology and what does it have to do with mathematics?
2) What is the method of
doubt test? What fails the test? What passes it? Why?