For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness;
Because that which may be known of God is manifest in them; for God hath showed it unto them.
For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
Because that, when they knew God, they glorified him not as God, neither were thankful; but bacame vain in their imaginations, and their foolish heart was darkened.
Professing themselves to be wise, they became fools,
And changed the glory of the incorruptible God unto an image made like to corruptable man, and to birds, and four-footed beasts, and creeping things.
Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonor their own bodies between themselves:
Who changed the truth of God into a lie, and worshiped and served the creature more than the Creator, who is belssed for ever, A-men.
For this cause God gave them up unto vile affections: for even their women did change the natural use into that which is against nature:
And likewise also the men, leaving the natural use of the woman, burned in their lust one toward another; men with men working that which is unseemly, and recieving in themselves that recompense of their error which was meet.
And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient;
Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers,
Backbiters, haters of God, despiteful proud, boasters, inventors of evil things, disobedient to parents,
Without understanding, covenant- breakers, without natural affection, implacable, unmerciful:
Who knowing the judgement of God, that they which comit such things are worthy of death, not only do the same, but have pleasure in them that do them.Romans 1:18-32 KJV, emphasis by me
They know, they always knew, and so do/did so many in our nation, as this passage describes them 2000 years before the fact. The problem with humanity is not that we don't know God, the problem is that we reject the knowlege of God.