Heaven and Hell.

Contention: That heaven and hell cannot coëxist in the same universe.

This argument draws largely on the same premises as the concept of “degrees of separation”. Take the saying “hell is other people” and turn it on its head. It is reasonable to expect that most people would not be content in heaven unless all their closest friends were there with them. (It doesn't matter if they don't arrive straightaway - they have their earthly lives to live out first, and some theologies hold that no matter when you die, everyone enters heaven at the same time because heavenly ‘time’ is different from earthly time — this also has the side-effect of allowing God omniscience without denying human free will. It also doesn’t matter exactly what your definitions of heaven and hell are, so long as they fit the overall category of “places of utter reward and punishment where you go depending on how you’ve lived in life”.)

Now, even assuming each and every one of those friends deserve to be in heaven too, they will want all their friends with them too. We can assume the heavenly deserts of every friend to a certain small number of iterations, if we began with a very saintly, intelligent and discriminating person to begin with - but the process goes on forever and our saintly person is a friend of a friend of a friend of (to the whatever power) someone who by the moral standards of even the most lenient judging God does not deserve a place in heaven, if the last judgment is to be at all meaningful. I mean, what sort of test is it where you are guaranteed to pass?

And if you were sent to hell, the exact same argument applies. So there could be heaven (if God is blindly kind, and doesn’t judge us after all), or hell (if God is sadistic and evil and everything we’ve been told he’s not). But there doesn’t seem to be any reason for either of them to exist any more.