Every once in a while, I like to post an article on Biblical epistemology. This is from IVP Dictionary of Apologetics.
“Unregenerate Knowledge of God,” by John M. Frame
Good teaching proceeds from the known to the unknown. So a good apologist will want to have some idea of what an inquirer already knows about God. Do non-Christians have any knowledge of the true God? If so, what do they know? In what ways does that knowledge manifest itself?
Scripture says that unbelievers know God (Rom. 1:21), but it also says they do not know him (1 Cor. 2:14, 15:34, 1 Thess. 4:5, 2 Thess. 1:8, compare 2 Tim. 3:7, Tit. 1:16, 1 John 4:8). Evidently, then, we must make some distinctions, for in some sense or senses, knowledge of God is universal, and otherwise it is not.
Rom. 1:18-32 is the classic text on this question. Here Paul stresses the clarity of God’s revelation to the unrighteous. God reveals his wrath to them (verse 18), and makes truth about himself ‘plain to them’ (19), ‘clearly perceived’ (20). That revealed truth includes his ‘eternal power and divine nature’ (20). It also contains moral content, the knowledge of ‘God’s decree that those who practice [wicked things] deserve to die’ (32). Significantly, the text does not state that this revelation in nature communicates the way of salvation. Paul evidently believes that this additional content must come through the preaching of the gospel (Rom. 10:13-17). Thus he warrants the traditional theological distinction between general revelation (God’s revelation of himself through the created world) and special revelation (his revelation through prophecy, preaching, and Scripture).
The knowledge given by general revelation is not only a knowledge about God, a knowledge of propositions. It is a knowledge of God himself, a personal knowledge. For Paul says, not only that the wicked have information about God, but that “they knew God” (21).
Nevertheless, according to Paul, the wicked do not make proper use of this revealed knowledge. Rather, they ‘by their unrighteousness suppress the truth’ (18). He continues, ‘although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. Claiming to be wise, they became fools…’ (21-22). Paul describes their foolishness as idolatry (22-23). In his view, idolatry is not an innocent search for the divine or the result of honest ignorance. It is, rather, willfully and culpably turning away from clear revelation of the true God. So it is ‘exchanging the glory of the immortal God for images…’ (23), exchanging ‘the truth of God for a lie’ (25).
Because they willfully turned from God’s clear revelation, God ‘gave them up’ (24, 26, 28) to serious sin, particularly sexual. Even then, however, the original clear revelation continues to function, for it serves as a standard of judgment. As Paul says, it leaves them ‘without excuse’ (20).
From this passage, we can understand the senses in which the unregenerate do and do not know God. They know God as they are confronted by his revelation. Other Scriptures tell us that this revelation is found not only in the natural world, but in their own persons, for we are all made in God’s image (Gen. 1:27). So God’s revelation is inescapable. But apart from the special revelation and saving grace of God, people exchange this truth for lies and engage in such wickedness that they become enemies of God, not friends.