Everyman is "enlightened" to God in some way or some manner through the pages of history all the way back to Adam. No man has an excuse to say there is no God.
1. God is revealed in nature. The creation of Earth and the creation of humanity "revealed" the Creator. The history of the Bible proves man (Jew and Gentile) is a violator to nature and the natural laws of Creation. Rom 1:19-20...Because that which may be known of God is manifest in them; for God hath shewed 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.
2. God is revealed through the standard of man since the Fall of Adam in the Garden. How? Man's natural inclination is in total rebellion to the Creator. The conscience of man is guilty, without strength, without hope, and helpless without God. Rom 2:12-15...For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law;(For not the hearers of the law are just before God, but the doers of the law shall be justified. For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another;) Man is a violator to the conscience.
3. God was revealed in the Law of Moses given to Israel on Mt. Sinai. The Law was given to reveal man's guilt and unholiness. Man could only keep the Law with his natural will and intellect. Israel was "enlightened" to God by the authority of the Torah before the Church was purchased and the Holy Spirit was given in the New Testament. God was also revealed in the flesh when Christ came during His earthly ministry. Rom 3:19-20...Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God. Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin. Israel was a violator of the Law of Moses before and during Christ's Earthly ministry.
4. God is revealed presently through the ministration of the Holy Spirit under the Grace Covenant...in the body of Christ, the Church. God is revealed to the heart of man through the Gospel message that pertains to the death, burial, and resurrection of Christ. Man is enlightened to God by the truth of the Word and the power of the Holy Spirit in the human soul that convicts, regenerates, and sanctifies.
5. No man anywhere on the planet Earth has the right to say there is no God.
6. Everyman is accountable to God...according to the enlightenment that has been revealed to his heart. All men will be judged according to their enlightenment. Rom 14:10-12...for we shall all stand before the judgment seat of Christ. For it is written, As I live, saith the Lord, every knee shall bow to me, and every tongue shall confess to God. So then every one of us shall give account of himself to God.