Meditation Five

Having proved God exists and is not a deceiver, Descartes turns next to considering "whether anything certain is to be had concerning material things." (87)

He turns to "ideas of these things, insofar as they exist in my thought". He finds distinct ideas of length, breadth and depth; size; shape; position and motion. (87)

But that's not all: "I [distinctly] perceive countless particulars concerning shapes, number, movement and the like."

Of these, he says that "even if perhaps they do not exist anywhere outside me, [they] still cannot be said to be nothing." (88)

An Example: "when I imagine a triangle, even if perhaps no such figure exists outside my thought anywhere in the world and never has, the triangle still has a certain determinate nature, essence, or form which is unchangeable and eternal, which I did not fabricate, and which does not depend on my mind." (88)

2 Connections to Plato:  (1) Notice the word 'form' (although don't take this to indicate that Descartes is a believer in the theory of forms).
(2) When I discover such ideas "it seems I am not so much learning something new as recalling something I knew beforehand." (87)

Do we see here "a basis for an argument proving the existence of God?" (88)

Descartes thinks so. He now presents what has come to be known as the Ontological Argument. This argument for God's existence is also associated with Saint Anselm (1033-1109), a great Catholic theologian and philosopher (and Archbishop of Canterbury) The Ontological Argument (Quickly)

"I have become accustomed to distinguishing existence from essence" (89)

E.g., I know what the essence of a triangle is, but I don't know whether any triangles exist. But God is a special case. "it is obvious to anyone who pays close attention that existence can no more be separated from God's essence than its having three angles equal to two right angles can be separated from the essence of a triangle" (89) Why can't existence be separated from God's essence? "I am not free to think of God without existence, that is, a supremely perfect being without a supreme perfection" (89)

Therefore, God exists.

Is this convincing?


The Ontological Argument Again (Slowly)

Reconstructing the Ontological Argument:

P1: God is the greatest conceivable being

i.e., a being whose essence includes all perfections (i.e., all 'great making properties').
P2: We have the idea of God

P3: Existence is a perfection.

Now, assume P4: the essence of God does not include existence

i.e., God doesn't exist.
P5: We can conceive of a greater being that God (from P3 & P4)
i.e., one whose essence includes all the same things as God's plus existence.
 P6: We can conceive of a being that is greater than the greatest conceivable being. (from P1 & P5) But that doesn’t make sense. We’re contradicting ourselves.

Something must have gone wrong somewhere, but what?

Either, we’re wrong to think that those premises lead us to this conclusion (but that doesn’t seem to be the case - the argument appears to be valid) or else one of the premises is incorrect – Anselm and Descartes think the best choice is P4.  Thus they conclude P4 is false.

What sort of argument are Descartes and Anselm presenting here?

Conclusion: It is false that God doesn’t exist in reality
i.e., God exists

Some Objections to the Ontological Argument

1. Attempted Reductios: Can we use this same argument to prove that other perfect things must exist? In Anselm's day, a monk named Gaunilo suggested that we could use the same argument to prove that the perfect island (that island which is greater than all other islands) must exist. Can we also prove the existence of the prefect ice cream cone, the perfect gorilla, etc.?  If so, isn't that enough to provide a reductio ad absurdum of the ontological argument.

A response: But all the argument shows is that if the perfect island doesn’t exist, it would be a greater thing if it did exist. It doesn’t say it would be a greater island.

So, then are we uttering a contradiction when we say that it is possible that the greatest conceivable island might not exist? In other words, is it contradictory to say that the greatest conceivable island does not have existence as part of its essence?

2. Does God really exist 'in our minds'? We might suggest that the logical paradoxes that seem to be involved in the notion of a perfect being indicate that the idea is really incoherent.  
Does a square circle exist in your mind?

Imagine something that is omnipotent. Can it create a boulder so large it cannot lift it? If it can, then there’s something it can’t do (i.e., lift the boulder). If it can’t, there’s also something it can’t do (i.e., create the unliftable boulder). Perhaps omnipotence is incoherent.

A Response? Perhaps God can't create a square circle or a boulder so large he can't lift it. However, maybe this isn't because he's limited, but because we're talking nonsense when we ask God to do these things.  
Does the phrase 'an object which is both a circle and a square (all over)' mean anything?   Does the fact that God can't 'dogface mambo the banana patch' constitute a limitation on God's part?
3. Is existence a property? Immanuel Kant (1724-1804) made this criticism famous. The O.A. seems to rely on the assumption that existence is what we could call a ‘great making property’, i.e., a property which makes a thing greater than it would have been if it didn't possess the property.

Kant famously objected that existence isn’t a property at all (and so, certainly not a great making property). Instead, Kant claimed that existence was what a thing had to have before it had any properties at all.

Is this convincing?

Descartes on whether existence is a property: "I do not see what sort of thing you want existence to be, nor why it cannot be said to be a property just like omnipotence – provided, of course, that we take the word 'property' to stand for any attribute, or for whatever can be predicated of a thing; and this is exactly how it should be taken in this context." (Fifth Set of Replies, AT VII 382-3)

Does Batman have properties? Sherlock Holmes? Austin Powers? [Philosophy 1200]