I got a comment that made me think about this again, so I figured I’d do a pretty brief write-up while I have a second. I do not find ontological arguments to be very compelling, and I believe that’s a common sentiment amongst theists as well; however, I will concede that I am not particularly well-versed in them either – just for disclaimer’s sake 🙂
The obvious way to begin is to put forward his argument (copied from Wikipedia, of all places; yes I’m ashamed):
- A being has maximal excellence in a given possible world W if and only if it is omnipotent, omniscient and wholly good in W; and
- A being has maximal greatness if it has maximal excellence in every possible world.
- It is possible that there is a being that has maximal greatness. (Premise)
- Therefore, possibly, it is necessarily true that an omniscient, omnipotent, and perfectly good being exists.
- Therefore, (by axiom S5) it is necessarily true that an omniscient, omnipotent and perfectly good being exists.
- Therefore, an omniscient, omnipotent and perfectly good being exists.
I’ll once again talk about possible worlds and the necessary and contingent propositions that make them up. Possible worlds can be see as a logical space where all of our coherent statements like, “Suzy could have eaten the cake” hide out – what we are saying is there is a possible world in which Suzy did eat the cake. There is, however, not a possible world where Suzy both ate all of and did not eat any of the (same) cake as that’s logically incoherent. Something is necessary if it obtains in every possible world. Something is contingent if it could either obtain, or not obtain, in a possible world. 2+2 = 4 is an example of a necessary statement, and the talk of Suzy and her cake is an example of a contingent statement. Since each possible world has the same necessary facts, the worlds are differentiated by their contingent facts.
Plantinga starts off with a couple definitions, and (4) unpacks the premise in a way that makes our previous paragraph very important to understand. By definition, remembering that maximal greatness means something with that attribute is necessary; it either exists in every possible world or no possible world. We can see this by remembering that each possible world shares the same necessary facts! So (4) puts this into a form of it is possible that X is necessarily true. We can further rephrase this by saying there is a possible world in which X is necessarily true… and, as should be clear, this means that X is necessarily true in every possible world (5) – including our actual world (6). I’m really abusing the bold and italics today :).
Obviously this hinges on whether or not such a being is possible, but Plantinga’s goal is not to prove that God exists. He merely wants to offer justification that a reasonable person could accept God’s existence. This is important since someone could just as easily run a counter-argument where they say it is possible that maximality does not obtain. From this leads the conclusion that maximality does in fact not obtain. It’s clear where the conversation heads, and it should also be clear why it gets such New Atheist mockery as they take it to be an argument that proves God’s existence. I’m reaching the end of what I feel mildly comfortable talking about, so until next time!