The Ontological Argument
Anselm’s Argument
So the fool has to agree that the concept of something than which nothing
greater can be thought exists in his understanding, since he understood what
he heard and whatever is understood is in the understanding. And certainly
that than which nothing greater can be thought cannot exist only in the
understanding. For if it exists only in the understanding, it is possible to
think of it existing also in reality, and that is greater. If that than which
nothing greater can be thought exists in the understanding alone, then this
thing than which nothing greater can be thought is something than which a
greater can be thought. And this is clearly impossible. Therefore there can be
no doubt at all that something than which a greater cannot be thought exists
both in the understanding and in reality.
Anselm’s Argument
1.
The greatest being conceivable does not exist in
reality
2. Something that really exists is greater than something
that doesn’t
-----------------------------------------------------------------------3. the greatest being conceivable is not the greatest
being conceivable
Anselm’s Argument
1.
The greatest being conceivable does not exist in
reality
2. Something that really exists is greater than something
that doesn’t
-----------------------------------------------------------------------3. the greatest being conceivable is not the greatest
being conceivable
-----------------------------------------------------------------------4. The greatest being conceivable does exist in reality
Gaunilo’s Island
1.
The greatest island conceivable does not exist in
reality
2. Something that really exists is greater than something
that doesn’t
-----------------------------------------------------------------------3. the greatest island conceivable is not the greatest
being conceivable
Gaunilo’s Island
1.
The greatest island conceivable does not exist in
reality
2. Something that really exists is greater than something
that doesn’t
-----------------------------------------------------------------------3. the greatest island conceivable is not the greatest
island conceivable
-----------------------------------------------------------------------4. The greatest island conceivable does exist in reality
Gaunilo’s Island
Anselm’s Reply

1.
2.
First Form
The greatest conceivable X does not exist in reality
Something that really exists is greater than something
that doesn’t
-----------------------------------------------------------------------3. the greatest conceivable X is not the greatest
conceivable X
A Contradiction
Anselm’s Reply

1.
2.
Second Form
The X does not exist in reality
Something that really exists is greater than something
that doesn’t
-----------------------------------------------------------------------3. the X is not the greatest conceivable being
Not A Contradiction
The Fool’s Reply
1.
2.
The greatest being conceivable does not exist in
reality
Something that really exists is greater than something
that doesn’t
The Fool’s Reply
1.
2.
The greatest being conceivable does not exist in
reality
Something that really exists is greater than something
that doesn’t
The Fool’s Reply
1.
2.
The greatest being conceivable does not exist in
reality
Something that really exists is greater than something
that doesn’t
The Fool’s Reply
1. The X does not exist in reality
2. Something that really exists is more Y than something
that doesn’t
-----------------------------------------------------------------------3. the X is not the most Y conceivable being
The Fool’s Reply
1. The X does not exist in reality
2. Something that really exists is more dirty than
something that doesn’t
-----------------------------------------------------------------------3. the X is not the most dirty conceivable being
Descartes’s Version
… whenever I choose upon any thought of the First and Supreme Being,
and as it were bring out the idea of him from the treasury of my mind, I
must necessarily ascribe to him all perfections … This necessity clearly
ensures that, when later on I observe that existence is a perfection , I am
justified in concluding that the First and Supreme Being exists.
Descartes’s Version
1. God has all the perfections
2. Existence is a perfection
-----------------------------------------------------------------------3. God exists
Descartes’s Version
Kant’s Critique
Being is evidently not a real predicate, that is, a conception of something
which is added to the conception of some other thing. It is merely the
positing of a thing, or of certain determinations in it. Logically, it is
merely the copula of a judgement. The proposition, God is omnipotent,
contains two conceptions, which have a certain object or content; the word
is, is no additional predicate – it merely indicates the relation of the
predicate to the subject. Now, if I take the subject (God) with alll its
predicates (omnipotence being one), and say: God is, or There is a God, I
add no new predicate to the conception of God, I merely posit or affirm
the existence of the subject with all its predicates – I posit the object in
relation to my conception.
Descartes’s Version
Kant’s Critique
1.
The attribution of real predicates defines the
conception of an object
2. The attribution of existence does not define the
conception of an object
-----------------------------------------------------------------------3. ‘exists’ is not a real predicate
Descartes’s Version
Against Kant
1.
The attribution of property predicates defines the
conception of an object
2. The attribution of existence does not define the
conception of an object
-----------------------------------------------------------------------3. ‘exists’ is not a property predicate
Descartes’s Version
Against Kant
4. ‘X’ is a property predicate if X is a property
5. ‘exists’ is not a property predicate
-----------------------------------------------------------------------6. Existence is not a property
Descartes’s Version
Against Kant
What makes existence a ‘perfection’ anyway?