Descartes’
Ontological Argument
for the Existence of God
and
Other Related Issues
Fall 110 951 Fall 2008
Descartes’ arguments for the existence of God are Ontological
Arguments: they are deductive and a priori proofs for the existence of
God. They aim to be the sort of argument such that if the premises are
true, then the conclusion must be true. Also, all of the premises are
purportedly knowable without experience; we should be able to run
through these arguments with logic and language alone. Given Descartes’
project in the Meditations, his method of doubt, etc.—given that he is
trying to build a foundation of knowledge of the world from the inside
out, as it were—it is important that his argument for God be a priori.
If it works, and if Descartes can prove that there is an all-perfect,
supreme, benevolent God, then he will have thwarted his skeptical
hypothesis of the evil demon, and knowledge of the external world will
come flooding back. So it is important that this argument works. Let’s
see if it does…
First we’ll look at his argument in Meditation Five, and then at the
one in Meditation Three.
The following argument is (loosely) pulled from Descartes’ Meditation
Five. He gives another version in Meditation Three, which is (usually)
seen as a slightly more complicated proof for the existence of
God. But this one, below, is supposed to be fairly
straight-forward and intuitive.
(A)
1. I have an idea of
a supremely perfect being, i.e., a being having all perfections.
2. Necessary
existence is a perfection.
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A supremely perfect being exists.
Actually, argument (A) seems to be much more of an argument than
Descartes himself believes is necessary. He says in the Fifth
Meditations (68):
“…whenever I am of a mind to think of a
being that is first and supreme, and bring forth the idea of God as it
were from the storehouse of my mind, I must of necessity ascribe all
perfections to him, even if I do not at that time enumerate them all or
take notice of them individually. This necessity plainly suffices so
that afterwards, when I realize that existence is a perfection, I
rightly conclude that a first and supreme being exists.”
His language here, and his discussion of clear and distinct ideas in
the sentences that follow it, suggest that his knowledge of God’s
existence is more immediate and straightforward than any deductive
argument, such as argument (A).
This is because underlying Descartes’ argument for God in the Fifth
Meditation is this notion of having a clear and distinct idea or a
clear and distinct perception of God. Clear and distinct perception is
something that he introduces as early on as Meditations Two. He
believes that the cogito—the conclusion “’I am, I exist’ is necessarily
true every time I utter it”(25)—is something that he clearly and
distinctly perceives. He then accept in Meditations Three a general
rule about the things that he clearly and distinctly perceives (such as
the cogito):
“…thus I now seem able to posit as a
general rule that everything I very clearly and distinctly perceive is
true.” (35)
Once this general rule is on the table, then if Descartes can clearly
and distinctly perceive that God exists, God must exist. And he thinks
he can clearly and distinctly perceive that God exists.
So this is why argument (A) is more of an argument than Descartes would
have wanted. Clear and distinct perceptions is immediate and direct; no
argument is needed once you have clearly and distinctly perceived
something.
But perhaps you are not persuaded that (i) Descartes’ rule that clear
and distinct perception leads to truth or (ii) that even if it did, you
disagree that we can clearly and distinctly perceive that God exists.
Let’s see if we can flesh out argument (A) a bit more, where these
assumptions made a bit more explicit. Then we might be better able to
see where Descartes’ argument goes wrong, if it does. Let us take
a look at argument (B):
(B)
1. I have a (clear
and distinct) idea of a supremely perfect being, i.e., a being having
all perfections.
2. Necessary
existence is a perfection.
3. My (clear and
distinct) idea of a supremely perfect being has necessary existence (as
a property).
4. If I have a (clear
and distinct) idea of something that has necessary existence (as a
property)—i.e., if I have a (clear and distinct) idea of something that
necessarily exists—then this thing
necessarily exists.
5. If something
necessarily exists, then it actually (actually) exists.
_________________________________________________________________________________________________________________
A supremely perfect being (actually)
exists.
Is argument (B) valid? Is it sound? If it is valid but not sound, which
argument do you think is false?
Descartes’ argument for the existence of God in Meditation Three relies
on his idea of perfection and his idea of a perfect thing. The idea
(roughly) is represented by argument (C):
(C)
1. I have an idea of
a perfect being.
2. Some things have
more formal reality (or perfection) in them than others.
3. If something, x,
has a degree of formal reality (or perfection) than something else, y,
could have caused x only if x and y have the same degree of formal
reality (or perfection).
4. I have less formal
reality (or perfection) than my idea of perfection.
5. So I could not
have caused my idea of perfection.
6. Only God, who is
perfect, has enough formal reality (or perfection) to cause my idea of
a perfect being.
7. Moreover,
existence is a perfection.
__________________________________________________________________________________________________________
God exists.
Is this argument more or less convincing than arguments (A) or (B)? Why
or why not?
Is there another way you think we can run an Ontological Argument?
I.e., can we get out of Descartes’ evil demon skeptical scenario by
proving an all-good God exists in some other (a priori) way?
For example, there are several versions of the Ontological Argument.
Two of the more famous ones are St. Anselm’s Argument for the existence
of God, and one involving possible worlds. We will talk about these in
class if we have the time. Go here
for a handout on Anselm's version of the Ontological Argument.
Page Last Updated:
Sept. 17, 2008