On How to Answer a Presuppositionalist

Tim Shaughnessy is posting at DC a one note song. It doesn't matter what tune we sing, his song remains the same:
Christianity only has ONE presupposition. We presuppose the truth of the bible. God and his word cannot be divorced and are synonymous with one another so we could also say that we presuppose the God of the bible as true.
Okay then, let's sing this note. Let's presuppose the Bible and the God in it, yes! But let's first understand the Bible and the God in it. Q.E.D.