It (truth) is written into their members, hard wired into their brain.
Atheist = Liar in denial of what he knows is the truth.
Romans 1
18For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness; 19Because that which may be known of God is manifest in them; for God hath shewed it unto them. 20For 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:
Atheist = Liar in denial of what he knows is the truth.
Romans 1
18For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness; 19Because that which may be known of God is manifest in them; for God hath shewed it unto them. 20For 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:
The people referenced in Rom 1, who hold the truth in unrighteousness, are backsliding, born again children of God. If we cannot see the possibility of ourselves, by our fleshly nature, in these scriptures, perhaps we are not as humble, as we ought to be.
The unregenerate, before he has been quickened by God, still has a heart of stone, that cannot be pricked, by God, to feel guilty of breaking one of God's spiritual laws. In regeneration God exchanges the heart of stone to a fleshy heart that can be pricked to feel guilty of breaking one of God's laws.
The different response of these two hearts, when being confronted with the accusation of crucifying Christ, is revealed in Acts 2:37 (the fleshy heart) and Acts 7:54. (the heart of stone).