Following Kuyper and Bavinck, Van Til so emphasized the antithesis between believer and unbeliever that many have concluded that Van Til cuts the unbeliever off from any point of contact whatsoever. Van Til’s system has been caricatured as one in which the believer and unbeliever inhabit two different worlds from which they can only shout their own particular claims at each other, but can never engage in any meaningful way at any point. The charge is that, for Van Til, the believer and unbeliever live in two antithetical, hermetically sealed, worlds.
But that is only a caricature of Van Til’s thought. For instance, he says in Common Grace and the Gospel:
Metaphysically, both parties have all things in common, while epistemologically they have nothing in common. (p. 9).
The believer and the unbeliever both inhabit the same creation. Both stand in God’s world. Both are recipients of God’s self-disclosure “in the things that have been made” (Romans 1:20). Furthermore, both the believer and unbeliever bear the imago dei. As such their conscience, informed by the “works of the law written on their hearts,” bears witness against all people of their sin and rebellion (Romans 2:15). In other words, when an unbeliever becomes a believer it is not as if he metaphysically becomes something other than what he was before. Rather, his covenantal status has changed from a child of wrath to a child of the Father. And with the transforming work of the Spirit, who works faith in the unbeliever-become-believer, we have received “the Spirit who is from God, that we might understand the things freely given us by God” (1 Corinthians 2:12).
So, not only is the covenantal status of the believer antithetical to that of the unbeliever, but so is his whole way of thinking. The believer, alone, has the mind of Christ (1 Cor. 2:16). It is true the believer still has indwelling sin, and so his mind needs to be progressively transformed (Romans 12:2). Nevertheless, the believer no longer knows God, the world, or himself in exactly the same way he did before the regenerating work of the Spirit. In fact, it is not just a matter of the believer thinking better, but he thinks differently now that he seeks to “think God’s thoughts after him.” In other words, the manner in which the believer knows is not quantitatively different than the unbeliever (the unbeliever may know a whole lot more than the believer about science, math, history, or even the Bible), but rather the difference is qualitative. The unbeliever cannot think truly about anything (because all his thoughts are darkened and informed by rebellion against the Creator). He has no capacity for true thinking about the world, himself, or God. Only the believer can think truly about the world, himself, and God. Of course, that does not mean the unbeliever cannot make a valid calculation (he can add two plus two), but he cannot think truly (in a way that takes “every thought captive to the obedience of Christ,” 2 Cor. 10:5) about this valid calculation.
It is in this sense that Van Til can say that the believer and unbeliever have nothing in common epistemologically. At the same time, every area of life becomes a potential point of contact with the unbeliever because both live in God’s world as his creatures. This, of course, makes evangelism and apologetics both imperative and possible.
Finally, now with an eye toward Barth, there are significant ontological and epistemological differences between Van Til and Barth which can be pointed up over the issue of the point of contact. Barth denies a point of contact, but Van Til affirms it. The question is: why? Answer that question and you are well on your way toward understanding the foundational difference between the two thinkers. And here is a hint for my Barthian friends: the difference is not because Van Til adopts an analogia entis metaphysic. In fact, he does not. And that will be an issue to address in a future blog post. Stay tuned!
 See John Warwick Montgomery, “Once Upon an Apriori,” in ed. E.R. Geehan Jerusalem and Athens: Critical Discussions on the Philosophy and Apologetics of Cornelius Van Til (Nutley, NJ: P&R, 1971), 380–92.
 See the very helpful exegetical comments on this verse in Richard B. Gaffin, Jr., “Some Epistemological Reflections on 1 Cor 2:6–16,” in Westminster Theological Journal 57:1 (1995), 103ff.