All theists believe—or should believe—that God’s existence is necessary in a metaphysically robust sense of “necessary”.
How, after all, could we unswervingly commit our lives and our futures to an ontologically fragile God, one who could—try as He might to avoid it—cease to exist? Or one who, because He simply got bored with eternity, commit deicide, thereby leaving in the lurch all those who have cast their eternal hopes on Him?
And how could God be deserving of all honor and praise if God ultimately owes His own existence to something else? If something else created God, then wouldn’t that thing, whatever it is, be more deserving of the divine title than the being that we call “God”?
Based on reflections of this sort, I believe that all theists should agree with (1) and (2):
- God is metaphysically necessary =def. (a) God exists, (b) God did not come into being, and (c) God cannot cease to be.
- God is metaphysically fundamental =def. (a) God does not depend for His existence on anything more fundamental than Himself, and (b) everything other than God in some way owes its existence to God (i.e., God is more metaphysically fundamental than anything else).
(1) says that God is metaphysically necessary in Himself. (2) says that God is metaphysically necessary for the existence of anything else. Together (1) and (2) entail (3):
- God is the unique, ultimate metaphysically necessary foundation of reality.
In other words, IF anything exists, then God exists and is the metaphysically necessary ground of being of everything else.
Many theists, however, have wanted to say that God is necessary in a further sense than indicated by (1)–(3). They have wanted to say that God is not just metaphysically necessary and the unique ultimate metaphysical foundation but also logically necessary in the sense of (4):
- God is logically necessary =def. The very idea of God’s nonexistence entails a contradiction.
The contradiction envisioned by (4) need not be one that we could easily demonstrate via formal logic. Instead, as Aquinas famously suggested (ST 1a.2.1), it might be the case that only God could see that the idea of His non-existence is contradictory because only God could have the comprehensive grasp of the infinite divine essence needed to see that. Regardless, I believe (4) is false, for reasons I will now show by means of a thought experiment.
The “null world” hypothesis
I define a null world as the supposition that absolutely nothing exists, ever has existed, or ever will exist. It’s a completely empty “world”. Of course, in expressing the idea that nothing exists, I am not suggesting that there is some “thing” called “nothing” that somehow “exists”. “Nothing exists” simply means “It is not the case that anything exists.”
My central claim is that the null world hypothesis does not entail a contradiction. How could it? Contradictions can only obtain where there exist two or more propositions that mutually exclude each other. But in a null world there are no propositions or truth-bearers of any kind. So there is no truth or falsity.
But, someone may challenge, if a null world obtains, then wouldn’t it still be true that a null world obtains? Wouldn’t it still be true in such a world that nothing exists? I respond: absolutely not. Such questions fail to take the null world hypothesis seriously on its own terms. If nothing existed, then not even the idea of nothing existing would exist. Nothing can be true or false IN such a world. When we describe or contemplate a null world we must do so from the outside, so to speak, using language and conceptual resources that exist in our world, the actual, real, non-null world. But it would be illicit to smuggle those resources into the null world itself.
Now, since there can be no logical contradictions in a null world, it follows that nothing, not even God, exists of logical necessity. Logically necessity is constrained only by the law of non-contradiction. Logic is purely hypothetical: IF such-and-such were the case, THEN such-and-such would also have to be the case. You can’t generate a categorical conclusion (“X exists”) from purely hypothetical premises. To establish the existence of anything, you have to start by assuming the existence of something.
This is why the ontological argument fails. There is no purely logical way to get from the mere idea of God as a metaphysically necessary and metaphysically foundational being to the actual existence of God as a metaphysically necessary and metaphysically foundational being.
To say that the existence of God, or anything else, is logically necessary is to commit a category error. It is to conflate a purely hypothetical form of necessity with a categorical necessity.