At bottom, it is really quite simple. As presuppositionalists employ the word, “presupposition” can be used both objectively and subjectively. Employed objectively, it refers to the actual transcendental foundation of universal meaning and intelligibility, namely, the triune God. Used subjectively, it refers to a person‘s most basic personal heart commitment, this commitment having (1) the greatest authority in one’s thinking, being the least negotiable belief in one’s network of beliefs, and (2) the highest immunity to revision. In matters of ultimate commitment then, if one is consistent, the intended conclusion of one’s line of argument will also be the standard or presupposition which governs one’s manner of argumentation for that conclusion—or else the intended conclusion is not one’s ultimate commitment at all. Something else is. For the Christian presuppositionalist, “the two concepts coincide, for his basic commitment is allegiance to the One who really is the foundation of all universal intelligibility.”
Believing that “the fear of the Lord is the beginning of knowledge” (Prov. 1:7), that “all the treasures of wisdom and knowledge are hidden in Christ” (Col. 2:3), and therefore that the triune God (and/or the self-attesting Christ) is the transcendental, necessary ground of all meaning, intelligibility and predication, the presuppositional apologist maintains that the truth of God’s self-authenticating Word should be presupposed from start to finish throughout one’s apologetic witness. Accordingly, while the presuppositionalist values logic he understands that apart from God there is no reason to believe that the laws of logic correspond universally to objective reality. While he values science he understands that apart from God there is no reliable basis for doing science. While he values ethics he understands that apart from God moral principles are simply changing conventions and today’s vices can become tomorrow’s virtues. While he affirms the dignity and significance of human personhood he understands that apart from God man is simply a biological machine, an accident of nature, a cipher. And while he values the concepts of purpose, cause, probability and meaning he understands that apart from God these concepts have no real basis or meaning. Therefore, he thinks the Christian evidentialist is being untrue to his own faith when he grants to the unbeliever the hypothetical possibility of this being a non-theistic world that can successfully function and be rightly understood in terms of the laws of logic and the human sciences. And to suggest that the law of noncontradiction, the “law of causality,” and “the basic reliability of sense perception” are more non-negotiably certain in this world than God himself is to deny the existence of the sovereign God of the universe “for whom and through whom and to whom are all things” (Rom. 11:36). To do so is also to abandon the Christ who “is before all things, in whom all things consist” (Col. 1:17), “in whom are hidden all the treasures of wisdom and knowledge” (Col. 2:3), and without whom man can do nothing (John 15:5). He reminds the evidentialist that it is not God who is the felon on trial; men are the felons. It is not God’s character and word which are questionable; men’s are (Job 40:1, 8; Rom. 3:4; 9:20). And it is not the Christian who is the unauthorized intruder in this world. This is his Father’s world, and the Christian is “at home” in it.
It is not then the Christian primarily who must justify his Christian presence in the world but the non-Christian who must be made to feel the burden of justifying his non-Christian views.
By presupposing the Triune God of the Christian Scriptures and the Scriptures of this God, with all of its truth statements, the presuppositionalist does not have to begin by developing intricate in-depth arguments to justify his employment of the law of noncontradiction, the law of causality, and the general reliability of the senses, for the Scriptures as God’s certain Word justify these matters for him. To illustrate, the Scriptures justify the legitimacy of the law of noncontradiction, first, by its assertion that every person, because he is the image of God, innately possesses the laws of reason as the bestowment of the divine Logos himself (John 1:3, 9), second, by the fact that the God of truth employs the Hebrew, Aramaic and Greek languages—which presuppose the laws of reason—to communicate his truth to the human mind, and third, by its many uses of various kind of logical argument and logical inference. It justifies the idea of causality with its employment of such words as כִּי, ki, יַעַן כִּי, ya˓an ki–, the preposition עַל, ˓al, with the infinitive, ὅτι, hoti; γάρ, gar; διά, dia, with the accusative case, and the causal participle. And it attests to the general reliability of the senses by declaring that all of man’s senses are of divine origination (Ex. 4:11; Ps. 94:9; Prov. 20:12), and these are represented in Scripture as playing a regular role in the acquisition and build-up of knowledge (Luke 24:36–43; John 20:27; Rom. 10:14–17; 2 Pet. 1:16–18; 1 John 1:1–3; 3:14).
The presuppositional apologist believes that his propagation and defense of the faith should be worked out then in a way which is consistent with his most fundamental commitment lest it become incoherent and ineffective. Accordingly, he does not believe that he can improve upon the total message that God has commissioned him to give to fallen men. Taking very seriously all that the Scriptures say about the inability of fallen man to understand the things of the Spirit (1 Cor. 2:14; see also Rom. 8:7–9; Eph. 4:17–18), he speaks God’s message, not to the so-called rational, neutral man who claims to be standing before him (this is fallen man’s erroneous presupposition about himself), but to the spiritually blind, spiritually hostile, and spiritually dead person who God says is standing before him. And he does this with the confidence that God’s Spirit, working by and with God’s Word, will regenerate the elect and call them to himself. Should the evidentialist object that the presuppositionalist is only “throwing gospel rocks at the unbeliever’s head” when he insists that the unbeliever must accept his biblical criteria for truth verification, the presuppositionalist, undaunted, will respond that he must continue to follow this approach just as the psychiatrist must continue to reason with a mental patient even though the latter lives in his own dreamworld and believes that it is the therapist who is out of his mind.
In his argumentation with the unbeliever the presuppositionalist is happy to employ all the biblical data and their implications for nature and history as (divinely preinterpreted) evidence for the truthfulness of the Christian position (and it is powerful evidence indeed). But he is unwilling to answer the “biblical fool” (that is, the unbeliever) according to his folly, that is, he will not argue the case for Christian theism utilizing the tests for truth of the unbeliever’s world-and-life-view, lest “he become like the fool” (Prov. 26:4). When he does “answer the fool according to his folly,” he does so only as an ad hominem, to show him the unintelligibility of this world without God and the dire results of living consistently with his godless world-view (of course, no unbeliever, as Francis Schaeffer consistently argued through the years, is living or can live consistently with his anti-theistic world view), and the presuppositionalist does so in order to keep the unbeliever from “becoming wise in his own eyes” (Prov. 26:5).
In conclusion, the presuppositionalist wishes the evidentialist would recognize that he too has his presuppositions as do all other people, and that he too reasons circularly. For instance, though the evidentialist will not permit the Bible to be self-authenticating, he presupposes (wrongly) that sensory data (cosmic, historical, archaeological, etc.) are self-authenticating, and thus he is as much a “dogmatist” on sensory experience as the presuppositionalist is on revelation. Hence the objection of circularity that the evidentialist levels against the presuppositionalist applies to himself with equal force. But his method, starting where it does, namely, with “uninterpreted” brute sensory data, is rendered logically invalid for the reasons stated in this introduction and thus can never arrive at the one living and true God or get the facts either.
~ Robert L. Reymond, A New Systematic Theology of the Christian Faith (Nashville: T. Nelson, 1998), 145-49.