Stephen Taylor - interesting point that you made earlier, that ontological naturalism (there is only nature) is on a a par with theism. Well, I think you were saying that.
I think you mean that neither can be defended. Well, there are obviously philosophers who are naturalists, but I'm not sure if they are 100% naturalists, and how they would argue for that. I suppose you could argue that we've never seen anything non-natural, therefore it is very unlikely that it exists. But then 'very unlikely' doesn't rule it out.
You could also argue that since the non-natural has never been defined, (and as you are saying, there is no method for demonstrating it), it can be dismissed. Hmm.
It's the point where the implausible becomes impossible, I don't know if there is such a point.
The comparison with the Matrix is interesting here - since the Matrix is very very unlikely and implausible, but I suppose one could stick one's neck out and say that it's impossible.