In the opening three chapters of Romans, Paul reasons his way to the conclusion that, “all have sinned and come short of the glory of God” (Roman 3:23), thus rendering all men everywhere and at all times justly condemned before God—whether they have heard the gospel or not; this sets up the need for all men to hear and respond to the gospel (Romans 1:16). Paul reaches his conclusion based on the witness of general revelation alone, which is and always has been available to all men (and which is consistently rejected by the natural man). This witness of general revelation comes in two forms: the creation (Romans 1) and human conscience (Romans 2). Consider Paul’s argument relative to the witness of creation in Romans 1:18-25.
The Universal and Sufficient Witness of Creation
In Romans 1:18, God asserts that the “ungodliness and unrighteousness of men” manifests itself as a “[suppression] of the truth in unrighteousness”. Note that it is not the case that some men do not have access to the truth, but that all men suppress the truth that they have. Furthermore, there is an agenda behind man’s suppression of truth; it is so that he can pursue “unrighteousness”.
In Romans 1:19, God asserts that He has supplied all men with a knowledge of Himself. God has not relied on men seeking Him, as He knows none will (Romans 3:11); rather, on His own initiative, God “hath shown it unto them”.
Romans 1:20 indicates this universal knowledge of God comes “from the creation” (i.e., the natural world all around us). Further, God asserts that this knowledge of Him is “clearly seen” and “understood”. The ramifications of this assertion are awesome. No one can legitimately claim they didn’t know or understand that their Creator God, to whom they are accountable, exists. Certainly many make this claim, but this is a “suppression of the truth” which they possess in their heart of hearts. It isn’t a matter of not knowing or understanding, but rather a case of “they did not like to retain God in their knowledge” (cf. Romans 1:28). This leads to the conclusion of the universal and just condemnation of all men.
Paul’s conclusion is that from the witness of creation alone, all men “are without excuse”. The Greek word apologia, rendered “excuse” in our English translation, means ‘a formal, reasoned, and logical defense’ (as in a legal, courtroom proceeding). Thus, there is no acceptable defense that can be offered for man’s rejection of the knowledge of God from creation. This alone renders all men under the just condemnation of God. Whereas no one can be saved apart from hearing and believing the gospel (Romans 1:16-17), all can be justly condemned whether they have heard the gospel or not. Put theologically, men can be condemned on the basis of general revelation (available to all), but men can only be saved on the basis of special revelation (available only to some).
Suppression of the Truth Necessarily Leads to Idolatry
Notice in Romans 1:21 how Paul’s reasoning proceeds from the preceding assertion (i.e., “they knew God” is now a presupposition from which he reasons). It is not the case that men don’t know God, they definitely do. Rather, the issue is that men who know God do not glorify or thank (i.e., acknowledge) Him.
It has often been observed that Scripture offers no formal proof for the existence of God, and the so-called philosophical proofs (i.e., the teleological, cosmological, ontological arguments) for the existence of God are not fruitful in leading men to believe in God (and even if they were valid, they only purport to prove the existence of ‘a god’, not the God of the Bible); it is not a matter of men lacking adequate information, but a suppression of the clear and sufficient information they have already. This has serious implications relative to evangelism and apologetics (which can never really be de-coupled). An evangelist/apologist ought never to accept an unbeliever’s demand for a proof for God’s existence before he will consider the claims of the Bible. The evangelist/apologist ought to begin with the presupposition that the unbeliever already knows God exists, but has willfully suppressed that truth in unrighteousness.
Furthermore, suppression of the truth (i.e., rejection of God’s clear revelation) always and necessarily leads to idolatry, introduced here as “vain . . . imaginations”. It is interesting that in the Greek text, the word translated “imaginations” comes from dialogismos, which connotes ‘reasoning with oneself’; it is not someone else that the unbeliever is trying to persuade that his unbelief is rational/logical, but above all it is himself that he is trying to persuade (i.e., he must rationalize his unbelief in his own mind). Realizing this helps us understand the essence of idolatry.
In both the Old and New Testaments, God’s priority in communicating His standard for man is always on the prohibition of idolatry (cf. Exodus 20:3; Deuteronomy 5:7; 1 John 5:21), even above immorality (per se). The reason behind this is that idolatry always (logically) takes place first, with immorality inevitably following (cf. Romans 1:18-32). Romans 1:18-20 indicates that God’s revelation of Himself in the creation (i.e., general revelation) is clearly seen by all men, everywhere. The unbelieving mind must re-engineer its perception of reality in order to suppress the implications of this clear revelation, which is his personal accountability to his Creator. This philosophical re-engineering of reality to suppress God’s clear revelation of Himself is the essence of idolatry . Once the creature’s accountability to his Creator has been rationalized away in his own mind, he becomes free to engage in any form of immorality ‘with a clear conscience’ (so to speak). This is why idolatry always comes first (even in our modern world), and this is why God’s prohibition of it always takes priority. In a certain sense, it is idolatry that intellectually enables immorality.
But this is foolishness (Romans 1:22). According to Scripture, the greatest possible folly is to deny the existence of the God of the Bible; “the fool hath said in his heart, there is no God” (Ps14:1; 53:1). Mark Twain, legendary for his skepticism toward Christianity and the Bible, offered the following definition: “faith is believing in what you know isn’t true”. By this he intended to imply that Christians know the Bible isn’t really true, but choose to believe it anyway; the Word of God asserts the opposite, that unbelievers know that their unbelief is foolishness, but pursue it anyway.
The unbeliever is compelled (being a rational creature since he has been created in the image of God) to rationalize his unbelief, and his construction of an alternate reality (Romans 1:23) to explain the basic questions of life is idolatry. In ancient times, this rationalization manifested itself as belief in pagan deities ; in modern times, it tends to manifest itself as so-called scientific theories purporting to explain the origin of the universe and all life in it by purely naturalistic mechanisms . Either way, once idolatry has rationalized away accountability to the God of the Bible, immorality emanating from “the lusts of their own hearts” quickly follows (Romans 1:24).
Finally, Romans 1:25 summarizes idolatry as the “[exchange of] the truth of God” (i.e., the revelation of God in the creation, in the human conscience, in Scripture, and in Christ) for “a lie”. The particulars of the “lie” have changed down through history. Today, they are most notably present in the wide-spread acceptance of the Big Bang cosmogony, evolution as the explanation of all life, and (as a result) secular humanism as the guiding ethic. But whether the rationalization is a pantheon of pagan gods or the godless assertions of modern science, it’s idolatry none the less.
 Even if man’s idolatry gives lip service to other ‘gods’, they are always gods made by men, fashioned after men’s likeness, acceptable to men, manageable by men (i.e., safe for sinners).
 No pagan belief system recognizes the Creator-creature distinction revealed in the Bible. Pagan deities may be quantitatively superior to ordinary men (i.e., smarter, stronger, faster, etc.), but they are never qualitatively different than men (Cp., Numbers 23:19).
 Richard Dawkins, arguably today’s most prominent apologist for atheism, has confessed that, “Darwin made it possible to be an intellectually fulfilled atheist”.