Since neutrality is unattainable for either the unbeliever or believer, and since they have conflicting ultimate standards for judging claims to knowledge, the task of apologetics will ultimately be carried on at a presuppositional level. Contrasting worldviews are being debated. Each worldview has its presuppositions about reality, knowledge, and ethics; these mutually influence and support each other. There are no facts or uses of reason which are available outside of the interpretive system of basic commitments or assumptions which appeals to them; the presuppositions used by Christian and non-Christian determine what they will accept as factual and reasonable, and their respective presuppositions about fact and logic will determine what they say about reality. Thus there can be no direct proof offered for the truth of either perspective; direct appeals to fact and reason are emptied of argumentative strength by the opponent’s presuppositions (with which he understands and accepts facts and logic in a different light altogether). The argument between believer and unbeliever must then be indirect, admitting the impossibility of a neutral approach to reasoning and facts which allegedly outside of an interpretive system. The argument must pit the unbeliever’s system of thought as a unit over and against the believer’s system of thought as a unit. Their overall perspectives will have to contend with each other, rather than debating isolated points in a piecemeal fashion.
When the Christian sets forth his outlook he will stress the kind of God to whom he is committed, the nature of the world in relation to God, and the nature of man as God’s creature.
~Greg Bahnsen (Presuppositional Apologetics: Stated and Defended; ch 1, pgs 15-16)