DON’T READ IF YOU HAVEN’T SEEN IT
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. For what can be known about God is evident within them, because God has made it evident to them. For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. For 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.
These verses imply that it is unnecessary for the Christian to try to prove the existence of God to people. They would suggest rather that every human being already knows at some level of consciousness or unconsciousness that God “is really there.” The unregenerate, of course, do all they can to suppress this knowledge (Rom. 1:18), although they are never completely successful. It is for this reason that the Bible speaks of the unregenerate person as both knowing God (Rom 1:21, 32; 2:14-15) and not knowing Him (1 Cor 1:21; 2:14; 1 Thes. 4:5; 2Thes. 1:8) at the same time, that is, he knows God is really there but he does not know Him savingly.
Obviously, there is some psychological complexity here: “The unbeliever knows things at one level of his consciousness that he seeks to banish from other levels… he knows God, he knows what God requires, but he does not want that knowledge to influence his decision, except negatively: knowledge of God’s will tells him how to disobey God.”
–A New Systematic Theology of the Christian Faith : Dr. Robert L. Reymond
Obviously there is some psychological complexity here. When I first read that, I wondered what exactly that looks like. After watching Shutter Island, now I know. Shutter Island and the Noetic Effects of Sin