Some poor logician my atheist friend sent me in a facebook post attempted to attack Plantiga’s Modal Ontological argument and did a horrible job. Find the article here.
First of all, what is PMOA?
He attacks it in 3 ways:
1 He attempts to say that the argument is logically valid but meaningless
2 He attempts to show the argument is informally absurd (ie leads to unreasonable conclusions)
3 He attempts to show the argument is formally absurd (reductio ad absurdum)
1 – He takes issue with the idea that we can both posit “X possibly exists” and “X is necessary.” He says this is the equivalent of simply saying that God necessarily exists. No shit! That’s the point of the argument! He doesn’t discredit the logic, in fact he agrees the logic is sound, rather, he attempts to tell us that it is meaningless. He does so by citing Plantiga saying that the argument doesn’t prove the God of the Bible, which it of course doesn’t, but Plantiga does, in the same statement, assert that it is rational to believe in the God of the Bible because of the argument. Is this a contradiction? No! Plantiga is stating that his argument supports the God of the Bible but is not able to single-handedly prove that God. In other words it is a partial, circumstantial and indirect evidence consistent with the Bible rather than an out-and-out mathematical proof. The argument is simply saying that if something could exist then something must also exist necessarily. It is a proof of the existence of at least something being necessary. Whatever that thing is, the argument simply defines as God. This doesn’t out-and-out prove the Bible but it is consistent with the Bible and it is not meaningless. Something exists necessarily. According to Christianity that something is called God.
2 – He tries to show the argument is informally absurd by replacing God in the MOA with Goldbach’s conjecture, an unproven mathematical conjecture. He seeks to “prove” this unproven conjecture and implies that, by doing so, he has invalidated the argument. His argument is in error and I will show you why in a second, but the hilarious part is that if he wasn’t in error it still wouldn’t invalidate the argument! Let’s say he correctly substitutes God with Goldbach’s conjecture…For all he knows Goldbach’s conjecture is true! He would have just proved it and yet is arguing against it! He would need to prove the conjecture false first, then go on to use the MOA to prove it true and in this contradiction that would prove that either the proof he used or the MOA was in error. He did not do this.
“The ultimate reason of things must lie in a necessary substance…and this is what we call God. .. God alone is the primary Unity, or original simple substance, from which all…are produced.” (Leibniz)
Regardless, his positioning of G’s Conj. was inappropriate. He substitutes MOA propositions 1 and 2, which read as follows:
1 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
2 A being has maximal greatness if it has maximal excellence in every possible world.
With the following:
1 If Goldbach’s conjecture is correct, then it is necessarily true.
This is an inappropriate substitution! His reasoning is that Goldbach’s conjecture would constitute a metaphysically necessary mathematical rule if it were true. While that is true, the thing that he overlooks is that the truth of metaphysical law is determined by God! In other words, metaphysical law is contingent not necessary. Furthermore in the absence of God, who makes knowledge possible, how would you know whether or not a mathematical law were true? If knowledge is possible, and I think it is, then it proves God’s existence. Not just any God, but the particular Christian God!
3 – Lastly he tries to show it is formally absurd by plugging in perfect evil instead of God. There are two problems with this method:
1 – It is impossible for a perfectly evil being to exist because 1) existence itself is a quality of goodness and 2) perfection is a quality of goodness. Therefore something would be less good than a perfectly evil being if it did not exist, was only mostly evil, or both. In any of these cases the idea of a perfectly evil being existing is a logical contradiction.
2 – If a perfectly evil being could exist then he didn’t manage to prove that God was perfectly evil simply by swapping words. Rather, he would have proved that a perfectly evil being exists, which doesn’t mean that God can’t also exist, it would mean there is both a good God and an anti-God. However, as already shown, an anti-God is a logical contradiction.
In conclusion Plantiga’s MOA holds as true and is consistent with, although only circumstantially evidences, the Christian Bible.