At the beginning of Chapter 1 of his “An Introduction to Systematic Theology” Van Til immediately states the main presuppositions upon which all apologetic activity – ultimately, all rational thought – rests.
Firstly, God exists. Secondly, He has revealed himself to Man in Scripture. Thirdly, Van Til presupposes that Reformed theology is the most consistent and complete systematization of Biblical truth (although he would surely claim that this point is demonstrable rather than merely a presupposition). Systematic theology is that discipline which considers Scriptural revelation as a whole and the truth about God then ordered into a coherent system. This point is important since the task of apologetics is to defend such a system of truth, not merely isolated propositions or facts.
To defend a false system of truth using the presuppositional method will necessarily fail since such a system will, at some point or other, be shown to be self-contradictory. To defend only a part of Scriptural truth will also fail unless that part gains its meaning from the wider context of the whole counsel of God. Defending the Christian “system” as a whole is a key step in the presuppostional apologetic method.
Scripture is not Man-centered. Nor, Van Til says, is it Christ-centered. Scripture is God-centered. Although it is true that we can only come to a knowledge of God through Christ alone, Christ is himself fully God and an inseparable member of the Godhead. All of Christ’s work, and the role that Man plays in the history of redemption, is a means to an end: to reveal and to glorify God.
Before we engage in an apologetic defense of the system of truth as expressed by Reformed theology, we must come to a knowledge of God. Scriptural revelation must not return to Him void, if that were possible. Truth is not merely to be defended but known, understood and believed. Our goal is to gain knowledge of the God who has revealed Himself in Scripture, first and foremost.