Consider this assertion:
“Dogs pee on brick walls.”
How would you discover if this were true or not? You’d have to go out and find a dog peeing on a brick wall! But then, the skeptic would demand that you prove it really is a dog! So, first, you’d have to properly define “dog” by appealing to a dictionary. But wait says the skeptic, why is the dictionary authoritative? You then appeal to majority opinion! “But wait!” demands the skeptic, how do you know the majority really approved? So, you appeal once more to another thing…then another…then another and another…
In order to prove A, you appeal to B. In order to prove B, you appeal to C…in order to prove C, you appeal to D…and so on ad infinitum! You’ll never be able to prove that Dogs pee on brick walls! (Scroungy mutts the world over bark happily at the news…at least until they read Van Til and find out that proof is possible after all!)
When a person makes an assertion that we as Christians disagree with, then…(in light of the above) we need to play the part of the skeptic. We need to dig into his assertion, and find out what lies beneath it. For example, in saying “Dogs pee on brick walls”…we are assuming what a dog is. We assume what a brick wall is. We assume we know what peeing is. Those are three “presuppositions” that must be true in order for the assertion to be true.
A presupposition is the term given to beliefs that stand behind various assertions. Any belief can be a presupposition. “There is ice in the freezer,” presupposes the belief that the “freezer is working properly.” It also presupposes the belief that “there was water in the freezer.” So the belief: “There is water in the freezer” is a presupposition…a presupposed belief that is taken for granted and implied by the statement: “There is ice in the freezer.”
When A is asserted, we need to look for what supports it (B). Then we need to look for what supports B, (C). We do this until we come to that final belief a person holds that is not authenticated by any supporting belief. If this belief is not self-authenticating in some way…then it is NOT the final link in the chain…we must keep searching.
In this sense (deconstruction), when we do “Presuppositional Apologetics”…we are searching for the ultimate or final presupposition that a person holds. The one belief that is at the very foundation of all his or her other beliefs. When we find it…we examine it, and see if it can authenticate itself, and see also if it is consistent with the rest of his beliefs.
I hope this helps clarify what a presupposition is, and how it is different from the mathematical concept of an “Axiom.” (Presuppositions can be axioms, and axioms can be presuppositions…but the two aren’t the same.)
Posted by shotgunwildatheart 
Posted by shotgunwildatheart
Posted by shotgunwildatheart 











