Epistemic Possibility Enough?

A legacy post originally published on November 28, 2008 at 3:01 PM
🔗 Epistemic Possibility Enough? by Mike Almeida

Pretend that the following argument is sound. Let ‘God’ abbreviate the indefinite description ‘a being than which none greater can be conceived’.

Argument EP

1. If God exists, then he is omniscient, omnipotent, omnibenevolent and necessarily existing
2. For all x, if x is omnipotent, then x can make it true that ~(water = H₂O)
3. It is metaphysically impossible that ~(water = H₂O)
4. There exist no omnipotent beings (From 2,3)
5. /:. God does not exist (From 1-4)

As everyone knows, it is necessary a posteriori that water = H₂O. And, as everybody knows, the proposition that ~(water = H₂O) does not express a contradiction. It is perfectly consistent with everything said so far that there is a world in which God does exist. That is, (6) is consistent with (1)-(5), (I use ‘epistemic possibility’ in (6) in the atypical way that Chalmer’s does).

(6) It is epistemically possible that God exists.

And if God exists in any world, then God exists in every world. Now, the crucial observation: The proposition expressed by ‘God exists’ is the same from the point of view of every world. That is, in any world in which it is uttered, the sentence expresses the same proposition. But the proposition expressed by ‘water = H₂O’ is not the same from the point of view of every world. From the point of view of some worlds, that water = H₂O is necessarily true, and from the point of view of other worlds it is just false. That’s how it can be true here that water = H₂O (the proposition expressed when the sentence is uttered here) and false here that water = H₂O (the proposition expressed when the sentence is uttered in world w₁₀₀₀) without contradiction. But the following two propositions are inconsistent: they cannot both be true here.

(7) God does not exist (i.e., the proposition it expresses when uttered here).

(8) God exists (i.e., the proposition it expresses when uttered in w₁₀₀₀).

So, does God exist here or not? Since it is epistemically possible that God exists, it follows that God exists in every world, including our own. How do we know? Look, if there is some world in which God exists, then the proposition expressed by ‘God exists’ is true in every world. But the proposition expressed by ‘God exists’ is the same in any world in which that sentence is uttered. But then the sentence ‘God exists’ uttered here, in the actual world, must express a truth. Therefore, God exists. But wait, (3) states:

(3) It is metaphysically impossible that ~(water = H₂O).

and (2) states this:

(2) For all x, if x is omnipotent, then x can make it true that ~(water = H₂O).

So how could it be true that God exists here? The right conclusion, I suggest, is that it is epistemic possibility that matters to proofs that God exists (or not), not metaphysical possibility. Or, rather, if God is epistemically possible, then God is metaphysically possible. But then (3) is true, but (2) is false, and argument EP is unsound.