In popular misconception today, the choice of an apologetical method facing a Bible-believing Christian is between arguing presuppositionally OR appealing to evidences from history and nature in support of Christianity. But that is entirely wrong. Presuppositional apologetics endorses and indeed encourages the use of evidences -- but not evidences offered in the "traditional" manner as an appeal to the authority of the unbeliever's (allegedly) autonomous reasoning. Unbelievers who are self-conscious in their autonomy will usually fight against the force of the "facts" to which we can appeal in favor of the Bible's veracity.
When unbelievers resist the factual arguments which apologists can and should readily set before them to confirm or defend the Christian position, Van Til said we must then realize and take seriously that "the battle is not one primarily of this fact or of that fact. The battle is basically with respect to a philosophy of facts.... No one can be a scientist in any intelligible way without at the same time having a philosophy of reality as a whole."1
The presuppositional use of evidences in apologetics recognizes that ultimately the intellectual conflict between believers and unbelievers is a matter of antithetical worldviews. We must show that the unbeliever's worldview, by which he wishes to oppose the claims of the faith, would not only preclude the facts of Scripture, but the very intelligibility of any facts about any subject whatsoever. For that reason Van Til was adamant that the apologist not make the mistake of pretending to be neutral or autonomous in reasoning, but present his factual defense in the right way and in the right light to the unbeliever. "Christianity does not thus need to take shelter under the roof of a scientific method independent of itself. It rather offers itself as a roof to methods that would be scientific."2
If the intelligibility of the inductive, empirical reasoning used by the unbeliever to oppose the faith is to make any philosophical sense, the unbeliever will need to affirm the Christian faith as his presupposition or worldview! The efforts of unbelievers should be turned against their own unbelief. That is simply the presuppositional way of defending the faith and pressing evidential arguments.
Is the evidential power of (say) Christ's resurrection lost when the evidential argument for it is presented to the unbeliever within the context of Biblical presuppositions? Not at all. Presuppositional apologetics calls for the Christian and non-Christian to set side by side their two worldviews and do an internal examination of them both (and their respective "inner logics"). In such a comparison the evidential power of Christ's resurrection is easily set forth.
Yet somebody might wonder: "But if the presuppositions already require that the Bible be true and thus that Christ rose from the dead, how could the evidence be impressive?" Well, after the game-winning shot at the buzzer has become a matter of past history, and even though we know the outcome of the game, we are still astounded by that shot and can watch it in awe when we observe the videotape reply of the game. The shot is still impressive, even when you know the context and outcome. And the resurrection of our Lord is far more impressive, even when we approach it within the context of the Bible's presupposed truth.
Christians should readily say to unbelievers: "Within our worldview the evidence shows that God raised Christ from the dead! (even more amazingly, He did it out of saving love for sinners like us) -- and your worldview has nothing as impressive as that, but actually makes nonsense out of history and science and reasoning." The choice should be obvious.
1. The Protestant Doctrine of Scripture, p. 51.
2. Christian Theistic Evidences, p. 56.