“Some say that God can be known from nature; others say that he can be known only by studying the Bible. What is the correct viewpoint?”
There are two vantagepoints to be considered by this question. God is revealed by both nature and the Bible — but in different ways.
First, it is clear that there is a threshold level of revelation that can be detected from a consideration of the data manifest in nature. The marvelous order characteristic of the Universe suggests an Orderer — a force of intelligence who “framed” it (cf. Heb. 11:3). This intelligence logically suggests a personality. David affirmed that “the heavens declare the glory of God; and the expanse shows his handiwork” (Psa. 19:1).
Paul argued that the pagan is “without excuse” in the worship of idols. And why was that indictment handed down? “For the invisible things of him since the creation of the world are clearly seen, being perceived through the things that are made” (Rom. 1:20). If it is the case that one can reason that “every house is built by someone” (Heb. 3:4), surely the logical person is forced to conclude that some Intelligence produced this Universe of which we are a part.
If a pair of pliers, consisting of only four parts, could not have made itself, how could a human body, with 100 trillion living cells, have been formed by accident (cf. Psa. 139:14)? That is not a sensible deduction.
The “fingerprints” of a Divine Being are all over the creation and only the fool denies that fact (Psa. 14:1).
From these considerations, however, one can only arrive at certain limited conclusions. He may surmise that the Force who made the world is both intelligent and powerful. From these basic facts, though, he can deduce nothing of the Creator’s character, or of his plan for humanity. The revelation of nature is only abstract.
On the other hand, the inspired documents, that collectively constitute the Bible, are an index into the moral qualities of the creative Force behind the Universe, who is specifically identified in the Scriptures as “God.”
In the Scriptures, which have been buttressed with a great variety of evidences that establish their claim of divine origin, we learn of Heaven’s love (1 Jn. 4:8; Jn. 3:16), as well as his mercy (Eph. 2:4), and goodness (Acts 14:17). We discover that we were created in the very image of God himself (Gen. 1:26-27), and endowed with freedom of will. And even though that freedom was grossly abused, and through sin we have fallen from our original communion with the Creator, the Lord has provided for us a way back to him — through the redemptive mission of Jesus Christ. These are concrete facts of historical revelation, and they can be learned only from the Scriptures.
And so, the final answer is this: God has made himself known in a general sense in the intriguing mechanisms of the created world, and he has revealed himself in a more specific way by means of the written documents of the Bible.
The two are not in conflict; rather, they complement one another.