[FOM] The characteristic S5 axiom and the ontological argument

Vaughan Pratt pratt at cs.stanford.edu
Thu Apr 9 20:21:36 EDT 2009

 From a mathematical standpoint I find it remarkable that those in 
possession of an argument for the existence of something seem to be able 
to get unique existence out of the same argument.  Plantinga has made a 
career of creating God from logic and statistics.  If, as he argues, it 
is likely that an entity exists meeting our criteria for godliness, then 
it would seem even more likely that there are say a hundred of them than 
one, and more likely still a thousand.

Given the size of the universe, any predicate whose satisfiability is 
within the realm of possibility is highly likely to be satisfied not 
just once but many times.  Any conception of God that happens, for 
whatever combination of reasons, to rule out the possibility of 
membership of God in this universe ensures of course that God does not 
exist in it.  Any other conception however is highly likely to admit 
many instances.  By far the least likely outcome is exactly one God, 
whatever conception of God one uses.  Monotheism is therefore the least 
plausible of all possible religious beliefs.  That more than half the 
planet is monotheistic is yet another bit of evidence for the thesis 
that humans aren't very good at probability.

Vaughan Pratt

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