[Paul] I want to move on to the ontological argument. I kind of understand that if a
maximally great being exists, then he exists in every possible world,
because that's what a maximally great being would need to do if he was maximal. But why,
if it's possible that he exists, that he must? That's the part I don't understand. [Craig] Okay.
You know it's so funny you should ask that, because just before we completed our Skype
call I was reading Anselm's Proslogium about the ontological argument, and the key idea here is
that in order to be maximally great, this being must be not only omniscient,
morally perfect, omnipotent, but he must also have necessary existence, because it's greater to exist
necessarily than merely contingently. So what that means is that if God exists in any possible world,
then he has to exist in every possible world, because that's what necessary existence means.
Necessary existence is to exist in every possible world. So either God
either exists in no possible worlds, to say he's impossible, or he exists in every possible world.
So if God exists in one possible world, he exists in all of them. Now another way of saying that
is to say if God's existence is possible, then it follows that God exists.
So what the atheist has to say, [okay] the atheist has to say, not simply that God does not exist;
the atheist has to say it's impossible that God exists. Because if he exists in any possible
world, if it's possible that he exists, then he exists in every world, including this one.
So the atheist is a lot more radical than we think. It's not just that God doesn't exist;
it's impossible that God exists. So I just invite people; I don't try to prove to them that God's
existence is possible. I just say what do you think? Do you think it's possible that God exists,
or do you think it's impossible that God exists? And I think the concept of God is a perfectly
coherent, possible concept, and therefore I think this is a good argument for God's existence,
remarkably. [Paul] It's that bit where we jump from that if it's possible that God exists,
he exists in every possible world. I can understand that, but... [Craig] Well you
made a jump there. [Okay] If it's possible that God exists, then he exists in a possible world.
If it's possible that he exists, then he exists in at least one possible world
[yes], that's what it means to say that something is possible. If I say it's possible
that you have red hair, that means there is a possible world in which you have red hair.
Or if I say it's possible that I weigh 300 pounds, there's a possible world in which I weigh
300 pounds. So if you say it's possible that God exists you're saying there's a possible world in
which a maximally great being exists. And then the next move is to say wait a minute, if he exists
in one world, he exists in all of them, because a maximally great being has necessary existence, not
just contingent existence. He can't just exist in some possible worlds but not all of them.
Otherwise it's not necessary existence. So if there's a maximally great being in one world,
he's in all of them, because he has necessary existence. [okay.]