Descartes’ Ontological
Argument
Born: 31 March 1596 in La Haye (now
Descartes), Touraine, France
Died: 11 Feb 1650 in Stockholm,
Sweden
Terminology of the OA
Descartes was primarily concerned
with God’s essence, or nature.
God’s essence is described by
showing his attributes, or predicates,
or perfections
Put Descartes into context
Anselm’s 11th c. argument:
1. God is that than which nothing greater
(more perfect) can be conceived
2. Ttwngcbc must exist, since an
imaginary being twngcbc would be less
perfect than a real being twngcbc.
Why was Anselm turned to
stone?
- because he could see into the future,
and had seen the work of 14,999 Alevel candidates who all wrote that his
ontological argument was a
“reductio ad absurdum”.
Then he saw what the 15,000th candidate
had written:
Anselm’s argument was a
“rectum ad absurdum”
Aquinas’ rejection (13th c.)
The OA only works if we know God’s
essence.
We do not know God’s essence.
So God’s existence can be known only by
our sense experience of the universe
(hence Aquinas’ 5 ‘Ways’).
Is that true
Ttwngcbc seems a reasonable place to
start.
Also, we could also say that we can have
an ‘adequate’ idea of an all-powerful /
perfect being without our having to be
able to work out every single attribute
that such a being would have.
Descartes
Assumptions:
1. Our senses can always deceive us
2. God exists to guarantee the
consistency and reliability of our
sense perceptions.
The lesson learned?
1. Doubt can be removed by returning to the
basics. With the mind, the fact that I think
gives me one fact about which I can’t be
deceived – I exist: CES
2. So with things, to avoid deception, I must
ask what is their essence – that part of a
thing about which there is no argument?
The essence of a triangle
3 sides, 3 angles
180 degrees
The essence of mountains
The essence of God
Existence
Perfection
Singularity
In fact: every perfection
A 2nd stage to the argument
As in Anselm II
We must distinguish between ‘ordinary’
existence and ‘necessary existence’
Things have contingent existence
The same is
true of
‘construct
things’ like
Pegasus
Bellerophon
riding
Pegasus
Pegasus has ordinary existence,
so like all contingent things,
might not exist
God must possess necessary
existence, otherwise he would
not be the supremely perfect
being.
The argument reformulated tin
response to Caterus
1. Whatever is of something’s essence must
be affirmed of it: e.g. “all mammals are
warm-blooded”
2. By definition, God’s essence is his
existence
3. Therefore existence must be affirmed of
God.
Objection 1: Hume
Hang on,
laddie,
No existential
statement can
be analytic –
they’re all
synthetic
J.L. Mackie

“It is not simply obvious and
indisputable that there cannot be
analytic existential truths”
Maffs?
 But maffs is logical, ‘God exists’ is a
factual statement.

Objection 2: Kant
Real predicates
can’t be rejected
(as with real
triangles), but
imaginary ones
can, as with
imaginary triangles
and imaginary
gods.
Yet More Kant
 Moreover,
sunshine, existence is
not a predicate: ‘exist’ adds nothing
to the subject in phrases like ‘cows
exist’
 Try
the effect of ‘it exists’
Kant once again
The same is true with describing God’s
other ‘predicates’ – omnipotent,
omniscient, omnibenevolent, etc.,
because our idea of God already
contains them
 So we can reject all of God’s supposed
predicates

Kant’s swansong
“The attempt to establish the existence of
a supreme being by means of the … OA
… is therefore so much labor and effort
lost; we can no more extend our stock
of [theoretical] insight by mere ideas
than a merchant can better his position
by adding a few noughts to his cash
account.”
The crucial word in the OA
if
All the OA does is to establish
possibilities
If God exists, then God exists
necessarily, omnipotently,
omnisciently, etc.
The problem is that there is no
guarantee that God does exist.
‘Wahoo, buddy!’ – Norman
Malcolm rides to the rescue
‘Ordinary’ existence is not a predicate,
but ‘necessary’ existence seems as if
it is. It tells you that God has to exist.
1. If God came into existence now,
he would be contingent, and so
would not be God.
2. Therefore if God does not exist
now, his existence is impossible.
[why?]
3. Therefore God’s existence is
either impossible or necessary.
4. God’s existence can be
impossible only if the concept of
such a being is self-contradictory
or logically absurd.
5. It isn’t, therefore God exists
necessarily.
6. So in the same way, God is
necessarily omnipotent and
omniscient.
This is an analytic existential truth,
in the same way that the infinity of the
sequence of prime numbers
(1,3,5,7,11,13 etc.) is an analytic
existential truth.
You either grasp this, or you don’t.
Once you do, no doubt remains as to
whether or not God exists.
Baloney, Mahoney
Any competent mathematician could
demonstrate the infinity of the
sequence of prime numbers as a
mathematical fact. It does not
require intuitive understanding,
only intelligence.
Moreover
Reduce: ‘a self-contradictory notion’ to (x)
And:
‘logically absurd’ to (y)
And:
‘God exists’ to (z)
Reduce Malcolm’s argument to:
not (x) + not (y) = (z)
(not s.c. and not l.a. = God exists)
But this equation can also be solved by:
not (x) + not (y) = not (z)
Not s.c. and not l.a. = God doesn’t exist
Malcolm – Darn it, let’s say
the OA has anti-real force.
This is the argument that the OA is an
argument for those who believe in God.
But:
1.
Either the OA works or it doesn’t
2.
If it doesn’t, what’s the point of
believers using it?
Alvin Plantinga
Plantinga as
the cavalry:
A modal version
of the OA
Modal Logic
- uses a system of possible but non-actual
worlds to give a framework by which
you can judge what is possible and
what is necessary in the real world
- it isn’t the ‘many worlds’ interpretation of
quantum theory
‘maximal excellence’
- a being having maximal excellence
is one possessing all the Cartesian
perfections: omnipotence,
omniscience, aseity, perfection, etc.
‘maximal greatness’
- a being possesses maximal
greatness if it possesses maximal
excellence in all possible worlds.
World-Indexed properties
1. Consider all possible worlds, and label
them W1, W2, W3, W4 and so on
2. Consider Gordon Brown in worlds
1,2,3,5,7,9,23,45,67,467,2385, etc.
3. To be the same GB in W467 as in W1,
GB in W467 has to have some
recognisable features
No WIPS here
To say that properties are worldindexed means:
1. For something to exist in more than
one possible world, it cannot vary
significantly from world to world.
2. Whatever is necessary or impossible
cannot vary at all from world to world.
(why not)
So the same is true for God
God could not vary at all from world to
world. A being who is not omnipotent in
W8 cannot be the same as a being who
is omnipotent in W1,W2,W3,W4,W5,W6
and W7, because a non-omnipotent
being would not be recognisable as
God.
Now follow the logic:
(1) We aim to demonstrate the existence of
God (a being with maximal greatness)
(2) Such a being must possess maximal
excellence in all possible worlds
(3) Because of WIPS, if we can show that there
is a being of maximal excellence in just one
possible world, then we have proved that
such a being exists in all possible worlds
4. There is a being of maximal
excellence in one possible world,
because the idea of such a being is
either necessary or impossible.
5. It can be impossible only if the
idea of such a being is s.c. or l.a.
6. It isn’t, therefore such a being
exists necessarily in one possible
world.
7. Whatever is necessary or
impossible cannot vary at all
from world to world.
8. So such a being exists in all
possible worlds.
9. Therefore God has maximal
greatness and necessary
existence: God exists.
Why doesn’t this work?
1. because: not …
2. We could have a term ‘no maximality’,
which is the property of no world
possessing a maximally great being, in
which case the same flow of argument
could be used to demonstrate the nonexistence of God in every possible world,
including this one.
Synthesis – the OA fails on 2
fronts:
1. ‘existence’ isn’t a predicate. As Russell &
Frege say: it’s an existential quantifier
- it means ‘are instances of’.
‘Tame tigers exist’ means: ‘there are instances
of tame tigers’, which I can only know from
experience.
I cannot know that ‘there is an instance’ of God.
Timmy
(2) Statements asserting God’s
existence are tautologies
‘God is an omnipotent being’
Reduces to:
‘God (an omnipotent being) is an
omnipotent being’.
This is a tautology - analytic / true by
definition / but factually true only if there
is a God.
Unpack ‘God’ – it is shorthand for a
number of predicates
Each concept/predicate you add just adds to
the tautology
E.g. ‘God (an omnipotent, omniscient,
immutable being who has necessary
existence) exists omnipotently, omnisciently
and immutably and necessarily’
ALL tautologies are analytic – they
are necessarily/logically true – they
have ‘de dicto’ necessity.
But they may be factually false,
because no analytic statement can
give you knowledge of the facts –
you have to know the facts first
There is one exception that
causes confusion
‘God has necessary existence’ is a tautology
(a being who possesses n.e. has n.e.
But we could say ‘God necessarily exists’
This isn’t a tautology, because it means:
‘a being who possesses n.e. must exist’
‘a being who possesses n.e. must exist’
But this may be false. ‘Having to exist’
is a predicate, and if God exists, he has
to exist, because then he possesses the
predicate of having to exist. But there is
still no guarantee that such a being
exists. If it does not exist, then
obviously it does not possess n.e.
Conclusion
‘God exists’ is analytic in form.
It may be either factually true or
factually false.
The OA fails.
Salvage
The 20th c. Swiss
theologian Karl
Barth thinks that
Anselm
intended his
argument as a
prayer
This is because
(1) Anselm starts and ends
Proslogium with a prayer, and
(2) He thinks that Anselm
received his definition of God as
ttwnccbc as a self-revelation
from God.
But
1.
Anselm says that he has been
looking for a ‘proof’, and now has found
one
2. He means it as an analytic proof.
3. If his argument was just a prayer,
why did Gaunilo object to it, and why did
Anselm take Gaunilo’s objection as a
logical objection to the argument?
Norman Malcolm again
The OA won’t convince atheists, and is an
anti-real argument – it ‘coheres’ with truth
in the believing community
Really? What use is an anti-real argument to
believers?
All the believers I know take ‘God exists’ to be
cognitive/factual
The value of the OA
1.
to ‘blood’ generations of
students and drive them insane.
2.
It is also a part of the history of
philosophy.