15 who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them)
15 who [who are of such quality—the very ones who]
These kinds of people are a case that could occur at any time.
show the work [singular = requirement] of the law written in their hearts,
The word “show” indicates that Gentile conduct demonstrates something of what God put on their hearts. “The work of the law” is some degree of disclosure about God mentioned in verse 14. “Written” parallels written on tablets of stone. While these Gentiles do not have written revelation from God, they do have a form of knowing God to which they are accountable.
It is not the law itself that is written on the hearts of Gentiles but the “work” (requirement) of the law. The manifestation of what is in the law is in the conscience of people in general.
their conscience [knowledge with self] also bearing witness [with],
The conscience is knowledge within the person that evaluates what is right. “Conscience” comes from two words: know and with. The conscience here is not a norm or standard of truth but an inner witness that indicates whether something is right or wrong. The conscience confirms instinctive knowledge about God.
The main argument of chapter two is that God will reveal His righteous judgment (2:5). What God writes on the heart finds a response in conscience. This inner sense of what is right is enough to pronounce judgment on people.
and between themselves their thoughts accusing or else excusing them)
The Gentile has a debate with himself. At some point he judges himself and at another point excuses himself. Both “accusing” and “excusing” (defending) are legal terms used in courts of law for defending self.
The simple point is that those without law have convictions about what they do. Gentiles have some form of guidance. They stand at the bar of their own judgment. Their conscience either adduces their character or condemns their character.
God gives man an inner monitor to assess what is right.
The conscience is an essential part of human nature, but it is not a completely trustworthy gauge of God’s will. It is possible to corrupt the conscience (Ti 1:15) and sear the conscience (1 Ti 4:2). There is, therefore, no man without the knowledge of God’s will.
We live in a day when people manipulate their consciences. This places the self at a supreme position. Any course of action is permissible in this case on the grounds that it does not offend our conscience. This is a subjective orientation.
He 9:14, how much more shall the blood of Christ, who through the eternal Spirit offered Himself without spot to God, cleanse your conscience from dead works to serve the living God?