the issue in question would never arise if theists do as you say, and suggest “sir. i think you might burn in hell for an eternity if you don’t have faith in jesus, but I have no way to prove it, can you show me how to demonstrate whether that is true or not?”.
the issue only arise because one would not be one a theist worthy of the name in the first place if one is so minded as to even consider such an approach.
the issue only arise because one would not be one a theist worthy of the name in the first place if one is so minded as to even consider such an approach.