Why you will never win an argument with a Christian apologist

Somewhat randomly (by way of a Facebook conversation) I stumbled across an old post on Common Sense Atheism , the archives of which still make for great Sunday reading, in which Luke Muehlhauser took famed theologian (well... among people who know about theologians) William Lane Craig on his bizarre rationale for believing in Christianity: the "self-authenticating witness of the Holy Spirit". I've always found it absurd, because simply believing that one can have a "self-authenticating" experience of the Holy Spirit requires that you already believe the propositions of Christianity to be true. Because obviously, if you are in the camp that believes the Holy Spirit to be imaginary, you can't well sincerely pray to and experience something that you don't think actually exists. This makes the foundation for Craig's faith the most atrocious example of circular reasoning since... well, since his rationale for believing in the Kalam, but that's a