Transcript Descartes’ Ontological Argument

The Ontological Argument
Michael Lacewing
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© Michael Lacewing
Anselm’s argument
• By definition, God is a
being greater than
which cannot be
conceived.
• I can conceive of such a
being.
• It is greater to exist
than not to exist.
• Therefore, God must
exist.
Gaunilo’s objection
• You could prove anything perfect must exist
by this argument!
• I can conceive of the the perfect island,
greater than which cannot be conceived.
• And so such an island must exist, because it
would be less great if it didn’t.
• But this is ridiculous, so the ontological
argument must be flawed.
Anselm’s reply
• An island wouldn’t cease to be what it is – an
island – if it wasn’t perfect. Islands aren’t
perfect by definition or ‘essentially’.
• God wouldn’t be God if there was some
being even greater than God. Being the
greatest conceivable being is an essential
property of God.
• God’s existence is therefore necessary, while
even a perfect island exists only
contingently.
Descartes’ argument (Med.
V)
• ‘It is certain that I…
find the idea of a God
in my consciousness,
that is the idea of a
being supremely
perfect: and I know
with… clearness and
distinctness that an
[actual and] eternal
existence pertains to
his nature.’
Descartes’ argument
• God is a supremely perfect being.
• (Necessary) existence is a perfection.
• Therefore, God (necessarily) exists.
A first objection
• There is a difference between thinking God
exists and God actually existing: ‘though I
conceive God as existing, it does not seem to
follow on that account that God exists’.
• Reply: unlike any other thing, ‘because I
cannot conceive of God unless as existing, it
follows that existence is inseparable from
him, and therefore that he really exists’.
– ‘the necessity of the existence of God
determines me to think in this way: for it is not
in my power to conceive a God without
existence’
A second objection
• Gassendi: I can conceive of God without
existence.
• Reply: it can be hard to realize, but all
divine perfections entail each other – e.g.
– If God is omnipotent, then God must not depend
on anything else.
– Therefore, God must not depend on anything else
to exist.
– Therefore, God must have necessary existence.
Pressing the second
objection
• Johannes Caterus: Descartes’ argument only
works if God exists, because only if God
exists, is God omnipotent, etc. The
interdependence of perfections shows only
that the concept of existence is part of the
concept of God.
• Reply: that was all it was intended to show –
that we can’t conceive of God without
existence. So God must exist.
A third objection
• Kant: existence is not a
‘perfection’, because it
is not a predicate at all.
– To say ‘x exists’ is not to
describe x at all or explain
what x is. Existence is not
part of the concept of
anything.
– To say ‘x exists’ is to say
that some real object
corresponds to the concept
of x.
Diagnosis: necessary
existence
• ‘necessarily, God exists’ v. ‘God exists
necessarily’
• ‘necessarily, God exists’ = it must be true
that God exists.
• ‘God exists necessarily’ = the type of
existence God has (if God exists at all) is
‘necessary’, i.e. not contingent, without
dependence on anything else.
• The ontological argument confuses the two.