This is the last post in our series on the Christian apologetic method of presuppositionalism. In this post we will be focusing on, what I take to be, one of the biggest philosophical blunders that presuppositionalists make. What follows is a quote from Cornelius Van Til, in his book The Defense of the Faith, that will help illustrate exactly the type of fallacious reasoning that is employed:
[I]t takes an ultimate cause, God, if there are to be genuine second causes. In other words, it is only on the presupposition of the truth of Christianity that science is to be explained. (p. 265)
The problem might not be apparent upon a cursory glance, but notice exactly what Van Til is saying here. First, he’s saying that God is the ultimate cause of everything that exists, and that it is only due to his existence that there are any subsequent and secondary causes or existents. Now this, for a theist like myself, is uncontroversial. But then Van Til claims that this fact allows us to presuppose the truth of Christianity, and that this act is what makes science possible. Again, a theist would most likely agree that since God exists and is the first cause, then all order and regularity—of which science is founded on--is ultimately attributable to him. But, this is not the same as saying, therefore, that we must presuppose the existence of God, much less the truth of Christianity. That is to say, to admit that God is first in ontology does not mean that God is first in epistemology—remember that a presupposition is an epistemological first principle.
The point here then is that the presuppositionalist is conflating the order of being (ontology) with the order of knowing (epistemology). The presuppositionalist is essentially saying that since God is the ground of our existence and being, then we must presuppose his existence in order to reason at all. But this is false, unless one assumes that the order of being is identical to the order of knowing. In fact, when bringing up this point to presuppositionalists in the past, some of them have claimed that perhaps, then, there is no difference between ontology and epistemology, or that ontology and epistemology are not so easily separable in our philosophies. Now, while the latter is plausible, the former is simply false. Take an example. I first had knowledge of my wife before I had knowledge of her parents, and therefore my wife is of a previous order in my knowledge than her parents. But obviously this does not entail that my wife existed before her parents! For to argue such a thing would be absurd, and it would be to conflate metaphysical domains. But notice that this is exactly what the presuppositionalist is doing, namely, equating ontology with epistemology—that is, arguing that the order of ontology determines the order of epistemology. And since presuppositionalism rests on such metaphysical confusion then we have warrant for dismissing it as an invalid method.
Now, not only does our current discussion demonstrate that presuppositionalism rests on fallacious conflations, but it turns the tables against the presuppositionalist himself. Apologist Norman Geisler articulates:
Certainly if there is a God and all truth comers from him, it follows that even the very criteria of determining truth from error will be God-given. But God is what is to be proven, and we cannot begin by assuming his existence as a fact. If we do not have any tests for truth with which we can even begin, we can never make truth claims nor can we even know something is true.
The point is that every proposition, whether presupposed or not, must be subject to justification and rational warrant to determine if it’s true. But arbitrarily assuming something to be true (i.e. God’s existence) in order to ground truth is nonsense. That is, you must first have a criteria of truth before a proposition can count as true, and, therefore, the existence of God (as well as all other propositions) must be subject to that criteria, and thus subject to our reason. Unfortunately, this is the complete opposite of what the presuppositionalist wants. He doesn’t want God’s existence, or the Bible, subject to our rational human criteria, rather he wants our rational human criteria subject to the Bible and God. But this simply isn’t possible given the way epistemology works. As I articulated in previous posts in this series, we simply cannot begin epistemologically with God or the Bible, because adhering to the truth of God’s existence or the Bible are endeavors that require previous epistemic and ontological premises to be true, and thus it requires that the former propositions are grounded the latter. That is to say, it requires that God’s existence and the truth of the Bible rest on propositions more fundamental than themselves, and thus the existence of God and the truth of the Bible cannot constitute presuppositions.