You're the pinhead who said, but cannot support, that "knowledge cannot exist without god."
Demonstrably false.
Oh, I'm sorry, you must have missed this:
1. Knowledge (logical, moral, geometric, mathematical and scientific) is not possible if God doesn't exist.
2. Knowledge is possible.
3. God exists.
This syllogism is logically valid, and its conclusion is factually true if the major premise is true.
Circular reasoning (or sometimes, begging the question) is not a formal logical fallacy, but a commonsense/pragmatic defect if, in this case, the major premise provides no independent, rational ground or empirical evidence for itself. A serious presuppositional syllogism purports that its major premise is derived from an independent, rational ground, namely, the rational exigencies of reality itself, as any counterargument launched against it is inherently contradictory or self-negating.
In the meantime, the major premise itself is not inherently contradictory or self-negating.
Go ahead. Try it. Forget about supposed informal criticisms for the moment, and, as an exercise in logic, attempt to overthrow the "truth" claim in the major premise with a logically consistent argument. I can confidently assure you that any attempt to do so will be inherently contradictory or self-negating, as in some way or another it will necessarily presuppose the very same major premise it purports to falsify in its refutation! Another way to say this is that there is apparently something wrong with the assertion of atheism that does not plague the assertion of theism. --M.D. Rawlings
"Demonstrably false", eh? Are you and PrachettFan related? He has a habit of dismissing facts or arguments with bald claims sans any discernible sign of argumentation, too.
Your initial objection is not valid against a presuppositional argument unless the major premise is in fact not derived from an independent, rational ground. I concede that presuppositional arguments like this one in particular are seemingly off somehow, but the reason it has endured is because of what happens with the attempts to falsify the major premise. It's almost as if, and this gets a bit esoteric, that God Himself is backing it. It's a declaration akin to I AM. It can be expressed in other ways, but I prefer this one for its elegant simplicity.