The question has been asked a couple of times now just what is meant by the Presuppositionalist when they claim that unbelievers “borrow from the Christian Worldview”, and so I thought it made sense to address this in its own post at this point.
In the Bahnsen/Stein debate, Bahnsen makes the following comments in his rebuttal to Stein regarding the laws of logic:
“As invariant, they don’t fit into what most materialists would tell us about the constantly changing nature of the world. And so, you see, we have a real problem on our hands. Dr. Stein wants to use the laws of logic tonight. I maintain that by doing so he’s borrowing from my worldview. For you see, in the theistic worldview the laws of logic make sense, because in the theistic world view there can be abstract, invariant, universal entities such as the laws of logic. Within the theistic worldview you cannot contradict yourself, because to do so you’re engaging in the nature of lying, and that’s contrary to the character of God as we perceive it. And so, the laws of logic are something Dr. Stein is going to have to explain as an atheist or else relinquish using them.”
In short, what Bahnsen means (and any other Presupper for that matter) is that unbelievers do not have a worldview (i.e. set of foundational presuppositions) that can make intelligible their use of logic, morality, science, etc. And so for the unbeliever to be consistent in their use of these things, they implicitly “borrow” from the Christian worldview which *does* contains foundational presuppositions which make these things intelligible.
The major thrust of the Presuppers’ argument is not that unbelievers do *not* make use of logic, morality, science, etc. But rather, it is that *if* their espoused worldview were true, *then* they would not be able to do these things. The argument points to the inconsistencies between what unbelievers do (on the one hand), and what they would be *able* to do (on the other) if Christianity were not true.
Van Til shares the story of a little child sitting on her father’s lap, and slapping it (only being able to do so because she sits on his lap in the first place) as a way of representing what the unbeliever is doing when they reject the existence of God. Their ability to make an *intelligible* argument (on the surface) depends on the existence of the very thing they are arguing against. As Van Til said – “Antitheism presupposes Theism”.
There is much more to be said about this topic, no doubt, but hopefully this is at least an initial answer to why Presuppers use the word “borrow” so often.