Although the light of nature, and the works of creation and providence, do so far manifest the goodness, wisdom, and power of God, as to leave men inexcusable; yet are they not sufficient to give that knowledge of God, and of His will, which is necessary to salvation; therefore it pleased the Lord, at sundry times, and in divers manners, to reveal Himself, and to declare that [revelation] His will unto His church; and afterwards for the better preserving and propagating of the truth, and for the more sure establishment and comfort of the church against the corruption of the flesh, and the malice of Satan and of the world, to commit the same [revelation which He had declared to be His will unto His church] wholly unto writing; which maketh the Holy Scripture to be most necessary; those former ways of God’s revealing His will unto His people being now ceased. (Westminster Confession of Faith, I/i)

The Confession begins by asserting that although all men and women know God at some level of consciousness or unconsciousness because of God’s revealing work both within them—that is, “the light of nature” within men and women (John 1:9; Rom. 2:14–15)—and all around them in both his creation and providential care (Ps. 19:1; Acts 14:17; Rom. 1:20), yet this general revelation is not sufficient to give to them the knowledge of God that is necessary for salvation. All it does is leave them in their idolatry without excuse (Rom. 1:20).

Therefore, the Confession continues, God revealed himself (propositionally) at many different times and in different ways and declared the content of that special revelatory activity to be his will for his church. This makes the Holy Scripture to be “most necessary,” the Confession contends (over against Rome and the Anabaptist mystics), “those former ways of God’s revealing His will unto His people being now ceased.”

These verses imply that it is unnecessary for the Christian to try to prove the existence of God to people. They would suggest rather that every human being already knows at some level of consciousness or unconsciousness that God “is really there.” The unregenerate, of course, do all they can to suppress this knowledge (Rom. 1:18), although they are never completely successful. It is for this reason that the Bible speaks of the unregenerate person as both knowing God (Rom. 1:21, 32; 2:14–15) and not knowing Him (1 Cor. 1:21; 2:14; 1 Thes. 4:5; 2 Thes. 1:8) at the same time, that is, he knows God is really there but he does not know Him savingly. Obviously, there is some psychological complexity here: “The unbeliever knows things at one level of his consciousness that he seeks to banish from other levels … he knows God, he knows what God requires, but he does not want that knowledge to influence his decision, except negatively: knowledge of God’s will tells him how to disobey God” (John M. Frame, Apologetics to the Glory of God [Phillipsburg, N. J., Presbyterian and Reformed, 1994], p. 8). Consequently, to argue as the classical apologist does that proving the existence of God is necessary, at least for some if not for everyone, is to imply that some people do not know God exists, that they are not “religious people,” and therefore that they are not guilty before God for refusing to worship Him—facts belied by Romans 1:18–2:16 as a whole.

Much more could be said about methodological natural theology, but suffice it here to say that nowhere does the Bible endorse the notion that general revelation was given to provide people the data by which they might, beginning from themselves, reason their way to God. The Bible introduces general revelation alongside special revelation to emphasize man’s guilt. The entire effort of Thomistic natural theology to discover God by natural reason apart from Jesus Christ must be judged not only a failure (see 1 Cor. 1:20–21) but also as an unwitting handmaid of the entire revolt of human philosophy against the necessity of special revelation. See Robert L. Reymond, The Justification of Knowledge (Phillipsburg, N.J.: Presbyterian and Reformed, 1984), 118–30...

Here is an affirmation of the necessity of Holy Scripture—necessary certainly for salvation and a knowledge of God’s will for his church, its most immediate areas of application within the context of the confessional statement itself—but necessary also for the justification of all knowledge and of personal meaning itself.

It is important that we clearly see that the Confession grounds its doctrine of the necessity of Scripture in two antecedent conditions that obtain at the present time, namely, (1) the insufficiency of general revelation, and (2) the cessation of special revelation. If general revelation is insufficient to provide that knowledge of God and of his will that is essential to salvation, and if special revelation has ceased, then one must go to Scripture if he would learn those things which are “necessary to be known, believed, and observed, for salvation” (I/vii). Moreover, it must be noted that to the degree that one believes that God still speaks directly to men and women today through prophets and glossolalists, just to that same degree he is saying that he does not absolutely need the Bible for a word from God, and accordingly he has abandoned the great Reformation principle of sola Scriptura.

Excerpts from Reymond's New Systematic Theology of the Christian Faith