A tweak to the ontomystical argument

In an old paper, I argued that we do not hallucinate impossibilia: if we perceive something, the thing we perceive is possible, even if it is not actual. Consequently, if anyone has a perception—veridical or not—of a perfect being, a perfect being is possible. And mystics have such experiences. But as we know from the literature on ontological arguments, if a perfect being is possible, then a perfect being exists (this conditional goes back at least to Mersenne). So, a perfect being exists.

I now think the argument would have been better formulated in terms of what two-dimensional semanticists like Chalmers call “conceivability”:

1. What is perceived (perhaps non-veridically) is conceivable.

2. A perfect being is perceived (perhaps non-veridically).

3. If a perfect being is conceivable, a perfect being is possible.

4. A perfect being is possible.

5. If a perfect being is possible, a perfect being exists.

6. So, a perfect being exists.

Premise (3) follows from the fact that the notion of a perfect being is not twinearthable, so conceivability and possibility are equivalent for a perfect being (Chalmers is explicit that this is the case for God, but he concludes that God is inconceivable). Premise (1) avoids what I think is the most powerful of Ryan Byerly’s four apparent counterexamples to my original argument: the objection that one might have perceptions that are incompatible with necessary truths about natural kinds (e.g., a perception that a water molecule has three hydrogen atoms).