I think that's the thing though - you're quite right, theism IS subjective, and I do have sympathy for believers who struggle to explain their views (or, perhaps I should say, the views of their god). I would for example have a similar problem explaining why I felt that my favourite sport was better than your favourite sport, precisely because it is subjective.
But that's the point that I really don't get - because it a particular brand of theism is correct, then that means that there IS a god behind it all, a being that can think so much more clearly than any of us, forsee all the potential problems and issues that would arise, and (one would think) be able to anticipate them all and deal with them in advance.
That's the rub of my question, really. Not "why are theists not good enough debaters to convince me", but "why did The God not provide such clear arguments that there would be no debate in the first place". I simply can't reconcile a Good God with a being that would countenance such ongoing and widespread confusion.
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Additional thought for consideration. Assume that we die (I think that's a safe assumption!) and we finally come face to face with The God, whoever it may be. Will that god be able to provide clear and comprehensive answers to all the questions we may have?
Regarding the first question as to why God didn't provide the clear arguments so there would be no debate in the first place, I have no idea.
Regarding the second question about God providing clear and comprehensive answers to all the questions we may have, I really truly hope so.