One of the arguments against TAG is the “tit-for-tat skeptic” argument. It goes a little something like this: “So you say that I cannot have knowledge of anything without God? Well, that’s just like Descartes’ evil demon scenario. You’re just using a skeptical threat argument against me except this time the evil demon is a benevolent Spirit. Your argument would slice against us both.”
This argument was recently used against Gene Cook of The Narrow Mind by a caller recently. www.tnma.blogspot.com
This ‘rebuttal’, of course, is either a misunderstanding of TAG or commits the straw-man fallacy. TAG is NOT a skeptical threat argument, but rather, it is an ANTI-skeptical argument. Its aim is to show the unbeliever that *his* worldview is the one that ***logically leads to global skepticism***. Stated very plainly, the unbeliever has misidentified the skeptic. It is the unbeliever who is the epistemological skeptic!
Just like Plantinga’s EAAN (i.e. evolutionary argument against naturalism) which many presuppositionalists use as part of TAG, TAG shows that, given the presuppositions of the unbeliever, the unbeliever undermines himself and destroys any possibility of warranted justified belief (again, given the presuppositions of the unbeliever’s worldview). Given the presuppositions revealed in Scripture, however, the Christian has every reason to believe in the possibility of knowledge. To state it again, it is the unbeliever who has misidentified the skeptic who is none other than the unbeliever himself!
Let’s take atheistic materialism, for example. Materialism states that everything that exists is matter, plain and simple. This also means that everything has a material cause, but of course, this would include the materialist and his thoughts! To quote Francis Crick, the co-discoverer of DNA and a materialist:
“The Astonishing Hypothesis is that ‘You’, your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behaviour of a vast assembly of nerve cells and their associated molecules.” –Sir Francis Crick, The Astonishing Hypothesis (New York: Touchstone, 1994), p.3.
Thus, you are nothing more than a lump of molecules that churns away according to natural law. *You are nothing more that a cog in the machine of the cosmos.* Thus, you, that is, your cognitive self-ego, are nothing more than an illusion. Indeed, it would be more apt to refer to you as ‘you’, and instead of saying, “You are…,” it would be correct to say, “ ‘You’ is…” since the ‘you’ is nothing more than a non-teleological assortment of atoms banging away in a non-teleological universe yielding non-teleological thoughts. To quote the population geneticist and materialist, J.B.S. Haldane:
“If my mental processes are determined wholly by the motions of atoms in my brain, I have no reason to suppose that my beliefs are true…and hence I have no reason for supposing my brain to be composed of atoms.” –J.B.S. Haldane, Possible Worlds (1927; reprint, New Brunswick, N.J.: Transaction Publishers, 2001).
This means that your thoughts are also illusions as well, and if your thoughts are illusions, then the thought that your thoughts are illusions is itself an illusion. Of course, this means that the thought of the thought that your thoughts are illusions of illusions is also illusory, and on and on it goes. Reductio ad absurdum. Q.E.D. The unbeliever’s worldview is self-refuting.
It is the materialist’s worldview which leads to the denial of the cognitive self-ego which, in turn, inevitably leads to the impossibility of knowledge. Indeed, it is like this for every worldview which teaches in an impersonal universe. It is only on the assumption of a Personal beginning to the universe from an eternal, self-conscious, Personal Being that man can be anything more than a cog in the machine of the cosmos. God must exist. Otherwise, knowledge is impossible. To quote Van Til, “If you cannot believe in God, then you cannot logically believe in anything else.”