[Because of the Fall] The intellect of fallen man may, as such, be keen enough. It can therefore formally understand the Christian position. It may be compared to a buzz-saw that is sharp and shining, ready to cut the boards that come to it. Let us saw that a carpenter wishes to cut fifty boards for the purpose of laying the floor of a house. He has marked his boards. He has set his saw. He beings at one end of the mark on the board. But he does not know that his seven-year old son has tampered with the saw and changed its set. The result is that every board he saws is cut slantwise and thus unusable because [the board is] too short except at the point where the saw first made its contact with the wood. As long as the set of the saw is not changed, the result will always be the same.
— Cornelius Van Til, The Defense of the Faith, 4th Ed. (ed. by K. Scott Oliphant; Philipsburg, NJ: P&R, 2008), 97
In this interesting book, Cornelius Van Til came up with an analogy to describe what he thinks is the Reformed view of the noetic effects of sin. Van Til's point that he is trying to prove here is that sin affects the intellect, and therefore unregenerate men cannot reason alright of the things of God. In this light, Van Til and his supporters critique Gordon Clark as being a "rationalist" because Clark believes that the thinking apparatus is not affected by the fall.
With this in mind, let us analyze this analogy. We note here that the carpenter in Van Til's analogy has a nice working saw, which is analogous to reason. However, his saw has been tampered with, so that he cannot cut the boards alright. This is supposed to be analogous to the Fall causing Man's reason to be defective so he cannot properly reason. Man's reason is therefore still working but fundamentally defective because of Man's fall into sin.
We note however that in this analogy, the carpenter tries to cut the board correctly. The problem is in his tampered saw which is not working as it should. The carpenter it seems genuinely attempts to cut straight boards, but his task is forever doomed to failure because of his defective instrument.
Translated into the picture of Man and reason, this is analogous to fallen Man being genuinely desirous to know God, but his reason is defective thus he cannot do so no matter how much he desires it.
Is this the picture of Man that we want to have? Scripture is clear that the problem with Man is ethical, something which Van Til did agree with in principle. If the problem with Man is ethical, then the inability of Man to know God is not because he is trying to know God and fails to do so because of his defective reason, but because Man does not want to know God and tries as much as possible to excise God from his world. It is therefore Man who uses his intellect to reject God, not that his defective intellect is trying to do the impossible task of knowing God.
Van Til's analogy is severely defective, and does not express the Reformed and biblical view of the effects of sin on Man. To think of reason as being a good saw with a defective set is to make the effect of the Fall in reason an intellectual defect; an ontological defect of reason.
If we believe that the Fall affected Man's reason ethically and not ontologically, then we must insist, using the same analogy, that the saw and its set are fine. The problem lies with the carpenter not his tools. The carpenter is in rebellion against his boss who has called upon him to cut wood boards in a certain way. The carpenter therefore [willingly] alters the set or just cut the wood boards any way he wants, so that the cut boards are not what they were supposed to be.
So deep is Man's rebellion against God from the time of conception that such rebellion may be done even at the subconscious level. Thus, Man may be deluded by his own intellect to believe he is "merely following the evidences" and therefore seen to be someone who objectively rejects God because his intellect has "deduced" that the Christian God does not exist. God and His truths are rejected a priori and then the unregenerate man's sharp intellect is left to figure out a working system that seems at least on the surface to be logical and consistent.
Van Til's analogy of the fallen mind is therefore flawed. Upon such flawed analogies, Van Til and his followers have attacked the teachings of Clark on this and other subjects. The reason of Man however is not ontologically flawed in unregenerate Man. Rather, the noetic effects of the Fall refer to the usage of reason contrary to its intended goal of receiving the revelation of God. There is nothing ontologically wrong with reason per se, and we should in this light reject Van Til's analogy of the fallen mind and the novel teaching behind it.
Of course, it may be asked, didn't Van Til say explicitly that the effect of the Fall on reason is ethical? Indeed, he did. But the issue is not whether Van Til said it, but whether his more detailed teaching on the topic supports his profession that the effects of the Fall pertain to the ethical aspect only. To attempt to hold to two contradictory position is impossible, yet Van Til it seems has no problems with believing in two contradictory things.