Existence can no more be separated from the essence of God than the fact that its three
angles equal two right angles can be separated from the essence of a triangleit isa
contradiction to think of God (that is, a supremely perfect being) lacking existence (that
is, lacking a perfection)it isnecessary for me to suppose God exists, once I have made the
supposition that he has all perfections (since existence is one of the perfections)Not that
my thought brings this about or imposes any necessity on anything, but rather the
necessity of the thing itselfforces me to think this. (44)
Descartes then adds further reasons to believe that his idea of God is “an image of a true
and immutable nature” (45). The broad outline of Descartes' argument, then, is this: he
grasps what he claims are mind-independent truths about the kind of thing God would be
if there were one. And uniquely, in the case of God,
end p.97
the mind-independent truths about the kind require that the kind has an instance. To try to
show why, Descartes tries to show that “God does not exist” entails a contradiction.
It is surprisingly hard to say exactly what this last phase of Descartes' argument is up to. I
offer three readings of it, one of which subdivides.
Meditation V: One Reading
On one reading, Descartes' premises are that
- If God does not exist, a being with all perfections lacks a perfection, and
- A being with all perfections lacks a perfection entails a contradiction.
If both are true, Descartes may think, then if God does not exist, a contradiction is true.
But (18) is ambiguous, between
18a. If God does not exist, then if anything has all perfections, it lacks a perfection, and
18b. If God does not exist, there is something with all perfections which lacks a
perfection. (Van Inwagen 1993, 80–81)
To get a valid argument with (18a), we must read (19) as
19a. If anything has all perfections, it lacks a perfection entails a contradiction.
But (19a) is false. That conditional does not by itself entail a contradiction. It entails only
that nothing has all perfections, which is what one would expect if a perfect being does
not exist. So if the argument including (18a) is valid, it is unsound.
For Descartes, God is the sole possible being with all perfections, and so (18b) amounts
to - If God does not exist, God exists and lacks a perfection.
(20) is false unless God actually does exist necessarily, in which case “God does not
exist” is impossible and so implies anything. But then why should an atheist or agnostic
accept (20)? It is on its face quite unintuitive. On another reading, (18b) asserts that if
God does not exist, He “is” there, in some sense of “is” compatible with nonexistence,
and has contradictory properties. This reading clearly commits us to a Meinongian
ontology of nonexistent impossible objects,
end p.98