Archive for April 2nd, 2022


Why the Ontological Argument doesn’t work

Back in the Rocket Car posting, we (following ol’ Gaunilo) showed, via a kind of reductio ad absurdum, that the Ontological Argument for the Existence of God doesn’t work (unless I have a really cool rocket car in my basement, which does not appear to be true).

Reductio arguments of this kind can be a little unsatisfying, because they just show that a thing is false, by showing that it being true would imply other things being true that we aren’t prepared to say are true. But they don’t tell us how the thing is false; in this case, the lack of a Z2500 Rocket Car in my basement doesn’t tell us how the argument fails, only that it fails.

But the other day, somewhere, I saw hints of an old refutation of the Ontological Argument that showed where it went wrong. I only glimpsed a few words of it, while looking for something else, and then forgot where or what it was, but a while later my brain said, “Hey look, I bet this is what that argument was saying!”, so here is that subconscious reconstruction. If anyone knows who made this argument, or an argument like it, anciently, do let me know!

Conversationally, the Ontological Argument goes something like:

A: Let’s define ‘God’ as that entity which has all perfections.

B: Okay.

A: Now, existence is a perfection, therefore since God has all perfections, God has existence, ergo God exists.

B: Wow!

The present argument against the argument changes the conversation, by having B point out problems in the underlying frame:

A: Let’s define ‘God’ as that entity which has all perfections.

B: We should be careful here, since there might not be any such entity. Let’s say instead that ‘God’ is defined as that entity which, if it exists, has all perfections.

A: Why do we have to do that? I can define ‘Humpty’ as a square circle, and that definition holds even though there are no square circles

B: Not really. If we define Humpty simply as a square circle, then if someone says “there are no square circles,” we can reply “sure there is; there is Humpty!”, and that’s wrong. It’s better to say that, strictly speaking, Humpty is a thing that, if it exists, is both a square and a circle. If it doesn’t exist, then of course it’s neither a square nor a circle, so we can hardly define it that way.

A: Hm, Oh. Well, if we define ‘God’ as something which … I guess … has all perfections if it exists, and then note that existence is a perfection —

B: We can conclude that God exists, if it exists! Much like everything else, really. :)

A: Wait, no…

The underlying observation here is that, strictly speaking, when we define or imagine something, we are defining or imagining the properties that that thing would have if it existed. If it doesn’t exist, of course, it has no properties at all. So when we imagine a seven-storey duck, we are imagining what one would be like if it existed. We aren’t imagining what it’s really like, because it doesn’t really exist at all, so it isn’t like anything; it isn’t a duck, doesn’t have seven storeys, and so on.

Therefore when we define God as having all perfections, we are actually saying that for any property which is a perfection, God would have that property if God exists.

And then the conclusion of the Ontological Argument will be just that God exists, if God exists; and that isn’t very interesting.

This isn’t an utterly formal (dis)proof, but I find it attractive.