Presuppositional apologetics as taught by Cornelius Van Til urges the Christian to argue with unbelievers in an “indirect” fashion, doing an internal analysis of the unbeliever’s worldview (his fundamental assumptions about reality, knowledge, and ethics) and comparing it to the worldview revealed in the Bible. Many students of apologetics have come to see the strength of this apologetical challenge when it is applied to the various kinds of views advocated by atheists or materialists. Given the presuppositions of the atheist, he could not make sense out of adherence to the laws of logic (as I tried to show in my public debate with Gordon Stein), nor could he make sense out of the principles and procedures of science itself (as I tried to show in my public debate with Edward Tabash). The atheist cannot give a rational account of the fundamental assumptions of ethics, either.¹ Atheism is philosophically unable to argue ethically, scientifically, or logically against the Christian faith.

The question sometimes arises whether the presuppositional method can argue as effectively against non-atheists, however. That is, students of apologetics wonder whether we can argue presuppositionally with unbelievers who adhere to false religious faiths. They might not seem to fall so readily into the philosophical problems of unbelievers who deny any supernatural reality whatsoever. How does a presuppositional apologist deal with someone who has another “god” or another religious book, etc.?

It is imperative that we bear in mind that Van Til describes the presuppositional method as from the outset setting forth and working with the distinctive doctrines of Christian theism (e.g., the Trinity, divine providence). Van Til's presuppositional method is concrete, not abstract or formal; he does not offer for dialog with the unbeliever merely the worldview of a generic god of some undetermined nature and character, but the specific and full worldview of biblical Christianity. That is why Van Til’s Apologetics syllabus and the book The Defense of the Faith both began with detailed statements of Christian theology. These were not simply a review, warming up to apologetics; they were for Van Til a defining part of the apologetical task. Accordingly, the presuppositional method is not at all amenable to use by “just any other religion” which competes with Christianity—as many critics have hastily suggested.

How does the apologist deal with advocates of other religious faiths, if he wishes to use the presuppositional method? The same way he deals with atheists and materialists, etc. By internally examining “the worldview” which is offered by whatever religious devotee is having the dialog with him. The formal fact that the opposing religionist speaks of “god” (or “gods”) is not a difficulty here, for they must define their specific concept of deity. Remember here the example of Scripture: “for their rock is not as our Rock” (Deuteronomy 32:31); recall the devastating prophetic critique of the heathen’s “lifeless” idols which are (contradictorily) under the sovereignty of those who bow down to them. The use of religious vocabulary and appeals does not change the applicability of the indirect method of disproving your opponent’s presuppositions.

Most unstudied (and overly general) comments by people about comparative religion—for instance, that “all religions are alike” or “you can have your pick of sacred books”—can be easily contradicted by the apologist. If anybody is tempted to be the spokesman and defender of “just any” non-Christian religion (so as to silence the Christian apologetic), it must be politely observed that the overwhelming and vast majority of world religions cannot even offer epistemological competition to the Christian worldview. They have no basis for “knowing” what they claim at all. Why? There are indeed other “sacred” books (Bhagavad Gita, Analects, Avesta, Adi Granth, Sutras, Tao Tsang, I Ching, etc.) but they are nothing at all like what the Bible presents itself as being. What does an internal analysis of the metaphysical and epistemological presuppositions of these different religions uncover?

Metaphysically, there is no god, or no personal god, or no god who is omniscient and sovereign, etc. Accordingly, from an epistemological perspective these “sacred” books are not and cannot be anything like what the Bible claims for itself, namely, to be the personal communication and infallible verbal revelation from the only living, completely sovereign, and all-knowing Creator. The other religious books, on their own presuppositions, give no reason to submit to them as true or normative; in terms of their own worldviews, these books as pieces of literature can have no epistemological or ethical authority. What they say (when you can make sense of it at all) could not be anything but simply “one man's opinion” against another man’s opinion!

The remaining world religions or cults which might begin to have something to offer in competition with Christianity (viz. a personal deity, a verbal revelation) are usually poor imitations of a quasi-Christian philosophical outlook (living on “borrowed capital”), or they can be treated as Christian heresies (borrowing or deferring to portions of the Bible itself or misreadings of it). Ordinarily the best tactic is to reason with such religious competitors from Scripture itself, then, refuting the departures and misinterpretations from what has been acknowledged as the Word of God. This too amounts to an “internal critique” of the worldview.

For example, parts of Sun Myung Moon’s teaching cannot be “authorized” by him simply with an appeal to the Bible, when he in fact rejects other aspects of the Bible and refuses to grant the Bible’s own claim to plenary authority. Without that plenary authority, no simple appeal to what the Bible itself says (without some other, outside warrant) can serve to “authorize” the point he is attempting to make. The apologist will then want to cross-examine this extrabiblical authority for its credentials.

In some people’s minds it is the Muslim faith, however, which presents a threat to presuppositional apologetics because, it is imagined, Islam can counter(feit) each move in the Christian’s argument. This, too, is an inaccurate preconception. The two worldviews are dissimilar in pivotal ways when one reflects on Islam’s unitarianism, fatalism, moral concepts, lack of redemption, etc. Islam can be internally critiqued on its own presuppositions. Take an obvious example. The Koran acknowledges the words of Moses, David, and Jesus to be the words of prophets sent by Allah—in which case the Koran may be, on its own terms, refuted because of its contradictions with earlier revelation (cf. Deuteronomy 13:1–5).

Sophisticated theologies offered by Muslim scholars interpret the theology of the Koran (cf. 42:11) as teaching the transcendence (tanzih) of unchanging Allah in such an extreme fashion that no human language (derived from changing experience) can positively and appropriate describe Allah—in which case the Koran rules out what the Koran claims to be.

Then again, the Islamic worldview teaches that God is holy and just toward sin, but (unlike the theology of the Bible—see here the words of Moses, David, and Jesus) there can indeed be “salvation” where guilt remains unremitted by the shedding of blood of a substitute for the sinner. The legalism of Islam (good works weighed against bad) does not address this problem because a person’s previous bad works are not changed by later good ones, but continue on one’s record in the very sight Allah (who supposedly cannot tolerate sin but must punish it).²

Thus, we see that Van Til’s presuppositional approach to defending the faith is an effective tool for responding to all kinds of unbelievers, irreligious and religious alike. That is because all men think in the context of a broader worldview which can be internally criticized, even if it utilizes “religious” concepts. The only religious concepts which can make philosophical sense out of life are those definite, concrete, truths revealed infallibly by God in His own Word.