We discussed St. Anselm’s ontological argument for God’s existence way back in Philosophy 1001 at the Georgia Institute of Technology 25 years ago. The argument has proven to be surprisingly resilient—and even my prof expressed admiration for it. At the same time, like most people, I fear that we’re playing with words more than saying anything about God.
Nevertheless, Christian philosopher Alvin Plantinga updated it recently. I’m posting it here not because I necessarily buy into it, but because I want to remember what it is, and this puts it rather plainly.
Premise #4 is the trickiest for me, but, as Wilson says, it follows from the meaning of “necessary.” Christian theology teaches that God is a necessary, rather than contingent, being; he doesn’t depend on anything else for his existence. You can substitute “maximally great being” for “necessary divine being.”
Anyway, for what it’s worth… From Andrew Wilson:
Here’s a quick, and surprisingly robust, argument for the existence of God. It amounts to a late twentieth century Plantingan rehash of Anselm’s ontological argument, and it goes like this:
1. It is possible that a necessary divine being exists.
2. If a being possibly exists, then it exists in some possible world.
3. Therefore a necessary divine being exists in some possible world (from #1, #2).
4. If a necessary being exists in some possible world, then it exists in all possible worlds.
5. Therefore a necessary divine being exists in all possible worlds (from #3, #4).
6. Therefore a necessary divine being exists (from #5).
The conclusion obviously follows from the premises, so the only question is whether the premises are probably correct. Both #2 and #4, in effect, are simply ways of stating what the words “possible” and “necessary” actually mean, and as such are not as controversial as they might appear. So the real debate is over #1 – but this, to most people, sounds intuitively correct. I’m not saying it will compel people to repent of their sins and follow Jesus, but it’s a good one to pull out at parties, isn’t it? (Presumably it depends on the parties.)