Evidential argument against God trumped

Philo asked:

Does the following successfully establish a presumption of strong global atheism?

“Define strong global atheism as the view that there is no god. There is a presumption of strong global atheism because theists propose the addition of a supernatural entity (a god) to what is already known to exist (the natural world). That is, theists make an extraordinary claim, and extraordinary claims require extraordinary evidence. In the absence of such evidence, strong global atheism is warranted.”

Answer by Gershon Velvel

As a would-be atheist, I am the first to admit that there is a lot of stuff I don’t know. To paraphrase a remark I heard somewhere, ‘there are unknown unknowns’. It’s bad enough not knowing stuff, worse when you’re not even able to form a conception of the kind of thing that might be missing from your inventory of knowledge.

Not knowing what I don’t know in relation to the God question, I feel somewhat queasy about any argument based on evidence or the lack of it. By saying that ‘evidence is required’, you are issuing a challenge, a challenge you believe cannot be met. But you are leaving the larger claim completely unchallenged: the claim that the God-hypothesis makes some sort of sense. If it didn’t make sense, how do you even know what you are talking about?

First of all, we need to explore a relative side issue. Does the claim that some ‘supernatural entity’ exists require ‘extraordinary evidence’?

It depends. The supernatural entity in question might be rather small and localized: a poltergeist, for example. Admittedly, if someone makes the claim that they have a poltergeist in their home, you are going to want to sift the evidence very carefully indeed. But if you are in the living room, with all your fancy electronic equipment, and objects start flying across the room for no reason at all, there comes a point where you have to say that the evidence of something matching the description of ‘poltergeist’ is overwhelming.

Is this likely to happen? I don’t believe so. David Hume in his Dialogues Concerning Natural Religion makes the point that even with seemingly ‘overwhelming evidence’ you have to consider the balance of probability: the chance that science is fundamentally flawed, and the natural world is not all there is, versus the chance that someone has played a very clever trick or that you’re having a hallucination, or whatever. But then again, if poltergeists became a regular occurrence, that argument would start looking rather thin.

Back to God. There is a case for saying that the flaw in the evidential argument gives the theist all they need. If you allow that the notion of God as a supernatural entity makes sense, then you have to allow that there is some possible world (I mean logically possible not ‘nomologically possible’) in which God exists. God isn’t just some very powerful supernatural being. (That would be the Devil.) God is a necessary being. So far as anyone existing in that logically possible world — call it the God-world — is concerned, God exists in ‘all possible worlds’. By a simple application of modal logic, if God exists as a necessary being in some possible world, then God exists in all possible worlds. Ergo, God exists.

I’ve just offered a version of St Anselm’s ontological argument updated with contemporary possible world semantics. As it stands it sounds pretty convincing, doesn’t it? Intuitively, it just seems a mistake to concede that much to the theist. Then again, maybe you could resist the argument by tweaking your modal logic so that ‘all possible worlds’ means something different in different possible worlds (look up ‘possible worlds’ and ‘accessibility relations’) but that looks like desperation to me.