Bahnsen then raises a most curious concern:
We have already seen that the presumption that knowledge must be "empirical" in nature is a mistake which can be easily corrected. And correcting this mistake does not in any way compel us to affirm or appeal to supernaturalism.
There are other difficulties with the position expressed by (1) as well. We can easily see that it amounts to a presupposition for the unbeliever. What rational basis or evidence is there for the position that all knowledge must be empirical in nature? That is not a conclusion supported by other reasoning, and the premise does not admit of empirical verification since it deals with what is universally or necessarily the case (not a historical or contingent truth). Moreover, the statement itself precludes any other type of verification or support other than empirical warrants or evidence. Thus the anti-metaphysical opponent of the Christian faith holds to this dogma in a presuppositional fashion - as something which controls inquiry, rather than being the result of inquiry. (Always Ready, pp. 187-188)
But Bahnsen wants to ask those who affirm that knowledge is empirical in nature, what rational basis they might have for supposing this. It may simply be that they do not know of a better way to express what they sense to be the case about the knowledge they have acquired. But if Bahnsen wants to know what rational basis one has for his suppositions, he should at the very least tell his readers what rational basis he might have for supposing that Christianity’s claims about “the supernatural” are true. Unfortunately, Bahnsen does not indicate any rational basis that his supernatural beliefs might have. In fact, he has only told us how his supernatural beliefs are not supported. For instance, their “support is not limited to natural observation and scientific experimentation.” They “do not stem from direct, eyeball experience of the physical world.” “They are not verified empirically in a point by point fashion.” “Empirical experience” must not be sufficient, for it “merely gives us an appearance of things,” and “the Bible distinguishes appearances from reality,” so there is obviously a conflict between how things “appear” to us and what they “really are.” Indeed, Bahnsen does not even explain what he means by “rational basis,” and yet he wants to know what “rational basis” others have for their claims, even though when he has an opportunity to identify any “rational basis” for his supernaturalism, he reneges on it. The consequence of this for Bahnsen is, obviously, if he has a problem with others not providing a “rational basis” for their position, he is quite simply a hypocrite for holding that against them.
Bahnsen wants to reserve the right to raise questions about what “rational basis” his adversaries might claim for their own positions, but when it comes time for him to defend his claim to “knowing the ‘super-natural’,” he's content to leave such concerns completely unattended. So when Bahnsen says that "everybody should be expected to play by the same rules" (p. 185), that holds only some of the time.
Bahnsen elaborates on the problem with empiricism as he understands it:
So what is missing? Does Bahnsen think that this problem is somehow overcome by belief in "the supernatural"? Would believing in "the supernatural" somehow make it sensible to assume that nature is uniform with itself? How would this follow? Bahnsen likes to raise problems, but doesn't explain how we can resolve them.
That anti-metaphysical presupposition, however, has certain devastating results. Notice that if all knowledge must be empirical in nature, then the uniformity of nature cannot be known to be true. And without the knowledge and assurance that the future will be like the past (e.g., if salt dissolved in water on Wednesday, it will do likewise and not explode in water on Friday) we could not draw empirical generalizations and projections - in which case the whole enterprise of natural science would immediately be undermined. (Always Ready, p. 188)
Let us entertain Bahnsen's supposition that "if all knowledge must be empirical in nature, then the uniformity of nature cannot be known to be true." Unfortunately, Bahnsen nowhere explains why this would be the case. Moreover, Bahnsen does not correct the error in the assumption that "all knowledge must be empirical in nature" by pointing out the fact that knowledge is actually conceptual in nature. Why doesn't he do this? I suspect there are two factors involved here: 1) Bahnsen does not understand that knowledge is conceptual in nature because he does not have a conceptual understanding of knowledge (and this in turn is due to the fact that the biblical worldview has no native theory of concepts); and 2) a conceptual understanding of knowledge would actually undermine the presuppositional apologetic, since presuppositionalism is geared toward exploiting Christianity's lack of an understanding of concepts in order to attack the human mind. In fact, had Bahnsen understood the nature of his mind and of knowledge before he became a Christian, he probably would never have become a Christian in the first place.
Also noteworthy is the fact that Bahnsen raises against non-Christians the very concern non-Christians could easily (and rightfully) raise against Christianity, given its commitment to metaphysical subjectivism, its lack of a viable conceptual theory and its moral proscriptions against autonomous judgment.
If I truly believed that the universe in which I exist were a creation of an invisible supernatural being which had the power to manipulate at any time or any place any object which exists in this universe, including myself, how would I know that salt would dissolve in water on one day, and not explode in water on other days? Bahnsen's mentor Cornelius Van Til tells us that the Christian god
On this "presupposition," the ruling consciousness ("God") could decide that, on Wednesday, it is a fact that salt dissolves in water, and on Friday, it is a fact that salt explodes in water. It can do this, according to Van Til, because "there is no inherent reason in the facts or laws themselves why this should not be done." It is simply setting the fact of how salt responds to water "into a new relation to created law," which it can do at will, and without advance notice or approval of the church elders. If one were to believe that such a thing as Van Til's god were real and active in the universe, where's this "assurance that the future will be like the past" that Bahnsen speaks of? If I truly believed that facts could be altered by the will of an invisible supernatural consciousness, how I could acquire the foreknowledge that it would or would not manipulate some object in my experience or some state of affairs in my life? How could I know that salt always dissolves in water? What if the ruling consciousness planned that later today salt will cease dissolving in water, and turn into rubber trees when it comes into contact with water? Surely the Christian believes that his god has the ability to do this. So what tells the believer that it won't do this or something else that is as absurd? What if the ruling consciousness is having a bad day, prone to wrath as the bible says it is? What if it's in a bad mood, and decides to send a tornado, earthquake, hurricane, or tsunami? Or, perhaps it decides to whip reality around such that utterly unpredictable chaos ensues? On Christianity's premises, we are to accept that such things are possible on the basis of the will of an invisible supernatural consciousness. But Christianity's defenders seem oblivious of the implications such views have for epistemology, which is utterly ironic given their characterization of rival positions.
may at any time take one fact and set it into a new relation to created law. That is, there is no inherent reason in the facts or laws themselves why this should not be done. It is this sort of conception of the relation of facts and laws, of the temporal one and many, imbedded as it is in the idea of God in which we profess to believe, that we need in order to make room for miracles. And miracles are at the heart of the Christian position. (The Defense of the Faith, p. 27)
Suppose I assumed what Christianity says is true, that there is an invisible supernatural being which can alter the facts of the universe at will. Even if I deluded myself into thinking I could forecast events before they happen, such as salt dissolving in water, my bus coming on schedule, or the sun warming the day, I do not know how I could acquire any degree of confidence in my forecasts, for my mind is not a supernatural mind, nor does my mind have the power to read the mind of any invisible supernatural consciousness (I cannot "think the thoughts" of an omniscient, infallible being after it, and I'm simply too honest to pretend that I can). In essence, all inductive generalizations and projections would be worthless. Some might perchance come true, but not because my inductive inferences were cogent. Only because my conclusions happened to coincide with the present wishes of the ruling consciousness would they seem to be true. Epistemology would thus be reduced to a crapshoot. But even here, “true” is a contextual assessment, and there would be no context corresponding to what actually happens available to me, for I would be unable to assume that the present is a reliable indicator of the future. If Christianity were true, as Van Til indicates, there would be no necessary relationship between an entity and its own actions, just as there would be "no inherent reason" why the ruling consciousness could not "at any time take one fact and set it into a new relation to created law." My "knowledge" would ultimately boil down to chance occasions of just so happening to get things right. And yet, this is the very same weakness that Bahnsen wants to charge against non-believing worldviews. Bahnsen thus hangs himself with his own rope.
by Dawson Bethrick