What is the significance of the statement in Romans 1:22 that "professing themselves to be wise, they became fools"?

Neither glorifying God in His works, nor thanking God for His temporal mercies, they lost the knowledge of God that they possessed. Refusing the witness of Creation, they fell back, as men are doing to-day, upon their own imaginations. Thus their foolish heart was darkened, that is, they lost the knowledge of God. Moral darkness is always, in Scripture, ignorance of God; even as light is the knowledge of God. The more foolish they became the more they professed to be wise: and the more they professed to be wise the bigger fools they became.

In the creation the Gentiles “knew God.” This is indeed not the conscious, vital knowledge derived only from new birth, but the distinct evidential knowledge that renders their guilt inexcusable. They wilfully refused to give God His own place: no pulsebeat of thankfulness would they have toward Him. They would receive His blessings, cut off the very hand that gave them, and proceed to pervert them to the full. The inward reasonings of their minds, because bent on following their own wills, dragged them into folly; and their hearts, wilfully without understanding, were colored by the darkness they chose. Moreover, the very reasonings that led them to such darkness they professed to be wisdom! — a profession which the more thoroughly declared them fools. This was their development — or evolution, if you will — “they became fools.”

Those peoples that are now heathen once knew God. Man's course has not been from polytheism to monotheism, as some dreamers would have us imagine, but the other way round. They have sunk out of light into the darkness. Once "they knew God", (v. 21) but the fact is, "they did not like to retain God in their knowledge." (v. 28.).

The root cause of their fall was that they did not wish to yield to God the glory that was his due, for they wished to pose as wise themselves — as we see in verses 21 and 22. In short, pride was the root and God has allowed them to make fools of themselves.

Their descent has been gradual. First vain thinkings: then, darkened understandings, gross idolatry, to be followed by outrageous sins in which they fell below the level of the beasts. Each generation went beyond the follies of their predecessors, thus ratifying for themselves the previous departure.

The next ground is not the knowable but the positively known. "Because, having known God, they glorified him not as God, nor were thankful, but became vain in their reasonings, and their unintelligent heart was darkened. Professing to be wise, they became fools, and changed the glory of the incorruptible God into a likeness of an image† of corruptible man and birds and quadrupeds and reptiles." (Ver. 21-23.) A traditional knowledge of God is in question; and as the former regarded man with evidence from the beginning calculated and adequate to indicate a divine First Cause, so the objective knowledge of God here spoken of was the portion of man even after the flood: indeed not till after that mighty event do we hear of idolatry. But man was unequal to the task of preserving the holy deposit; and this, because of his moral state. When they did know God, they neither glorified Him as such, nor were they thankful. This left room for vain reasonings, which again darkened the heart instead of leading it into light. It was the self-sufficiency, and so the folly, of the creature. For light is only seen in God's light, and man must sink into darkness when not morally elevated by looking up to One above him. The humbling proof appeared too soon; and philosophy but sealed the evil to which superstitious fear led the way. An unacknowledged Supreme was rapidly forgotten, and the glory of the incorruptible God exchanged for a likeness of an image of corruptible man, yea, into objects ever lowering till creation's lords, now the victims of this debasing delusion, worship the most loathsome reptile which eats the dust.

They knew God and glorified Him not. They turned away from the light. Here is the true law of evolution, not an evolution upward as taught so much at the present time, but an evolution downward. The ascent of man is a delusion; the descent of man is the truth. The only possible way of lifting man, who has fallen so low, yea beneath the beast, is the Gospel of Jesus Christ. "They became vain in their imaginations." The word imagination means, perverse, self-willed reasonings revealing the evil heart beneath from which they spring. Then their foolish heart was darkened. The next step down is that they professed themselves wise and became fools. Rejecting the light and turning away from God, they became philosophers and thought to find out things by searching. Idolatry was the next step. "A god, in some shape, is a natural necessity of man. His natural desire, in his first apostasy from truth, is a god after his own heart." A brief history of idolatry is given. First they changed the glory of the incorruptible God into a likeness of an image of corruptible man. But they did not stop with this, but they worshipped birds, four-footed beasts and creeping things. Birds, flying through the air, therefore considered nearer heaven, are put above the quadrupeds, which walk on the earth and the creeping things, which cannot rise out of the dust and mire of the earth are the lowest form. They worshipped the serpent, as it is still done by the Indians in Arizona. And idolatry is not confined to the heathen nations, it is practised in that great apostate system Romanism. A piece of bread, under an elaborate ritual, is lifted up and claimed to be changed by a few words of a sinful man, into the body and soul of the Son of god; then they fall down and worship. The mass is a blasphemous idolatry.

The Comtean worship reveals more than this (for in truth it is humanity that man, fallen away from God, everywhere worships. He may invest this with more or less of the attributes of deity: because he is not a being groping his way out of native darkness, as so many would persuade us; the inspired version of heathenism is more honoring to God, if more condemnatory of the creature, that "when they knew God, they glorified Him not as God, but became vain in their imaginations, and their foolish heart was darkened." They had not to invent God, but rather to invent the god that they desired; and the god that they desired was one like themselves, a being who could sympathize with the lusts and passions of a corrupt nature. Hence "professing themselves to be wise, they became fools, and changed the image of the incorruptible God into an image made like to corruptible man."

Idolatry, therefore, is apostasy. The only development that Scripture records is a development away from God. "When they knew God, they glorified Him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened. Professing themselves to be wise, they became fools, and changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things." Notice the order here. Idolatry makes progress, but it is in degradation. First, man who was made in the image of God is deified; then birds of the air, fourfooted beasts, down to the groveling, creeping insects, show the progress of degradation. Thus, in the magnificent temples of Egypt, where architecture reached its culmination of grandeur, we have stately avenues leading up to grand temples with their outer court and inner sanctuary, but enthroned in the innermost recess of this magnificence is a hideous scarabus, a creeping thing, as though Satan delighted to insult God by such a similitude.

Now it is a fact that there is inborn in the human race the feeling that the shock of death does not kill the soul, but that beyond death individual conscious existence will continue. This and the sense that there is a higher and unseen power have been the most potent instincts in the hearts of men throughout all their generations The earliest records that have been discovered by the excavators show that this was the dominating factor in the lives of the ancients, the master-thinkers of Greece, before Christ came, incorporated it with their systems of philosophy, and it matters not how degraded men may have become from their primitive dignity, or what they may have lost of the knowledge that their forefathers possessed, they have not forgotten this. The missionary from Christian lands has no need to tell the aborigines of Australia or the cannibals of the South Sea Islands that death will not be the end of them, they know it already. It is a fact that cruelty and superstition are associated with their belief of it, but the secret as to this is revealed in Romans 1:21-22, “Because that when they knew God, they glorified Him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened. Professing themselves to be wise they became fools.” The darkness that is the result of turning from God to the devil has deepened about the minds and hearts of these poor wretches as the centuries have rolled on. Yet this remains embedded in their very consciousness, that the soul of a man survives the death of his body.

The position was this. A new and terrible form of evil had been introduced into the world since the flood in the shape of idolatry. Men did not like to retain God in their knowledge, and so fell helplessly into the hands of Satan. "Professing themselves to be wise, they became fools." Idol-worship is in reality demon-worship (1 Cor. 10:20). Both Noah and Shem were still living when this new departure began, but their influence appears to have been nil. The new torrent of iniquity swept all before it. Then it was that God stepped in, and made Himself known to Abram, in grace giving him magnificent promises, which went far beyond his own need, comprehending in their scope the world at large to the utmost bounds of time.

For instance, the heathen often are spoken of as groping after the light and unable to find it; and it is looked upon as their misfortune, not their sin, because they are bound down by circumstances too hard for them. Now that is not really so. The truth is, "There is none that seeketh after God." God's account of it in the first chapter of the Epistle to the Romans is a totally different one. God states there by His apostle that, "When they knew God, they glorified Him not as God, neither were thankful, but became vain in their imaginations, and their foolish heart was darkened." That was the beginning of heathenism. It is man,not seeking God, but endeavoring to escape from God, and has escaped, so to speak, into the darkness. The darkness is the darkness of resisted light, not the absence of light. The light has not been absent. The very character of the darkness shows that it has not.