I've been having a lot of discussions about presuppositionalism when it comes to belief in gods. A lot of believers are invoking it even when they don't know it's name. They assume that the existence of their god is a given and that it therefore falls to non-believers to prove otherwise. It's an extremely dishonest tactic by attempting to reverse the burden of proof.
As I like to say, if I have to prove your god isn't real then you have to prove I'm not your god testing you.
I ran across an old comic that neatly demonstrates the problem with presuppositionalism and the way it's applied in debates over evolution, cosmology and so forth. I hope you enjoy it as much as I do.