Conscience involves a recognition of personal responsibility (2 Cor. 5:10). We all have a conscience because we all must give an account for what we do with the freedom and power God has given us.
How do we know what God expects?
We first learn what God expects from the law. God gave us the law to assist us in looking at ourselves through His eyes. The law shows us that sin is repulsive in God’s eyes. A guilty conscience is one that looks at its own soul through the eyes of the law and sees the stain of sin.
The law, however, is not the final measure of conscience. It is only a "tutor" that leads us through childhood toward a more mature relation in which we come to see God as a Father. (Gal. 4:1-7)
We learn to see God as a Father by looking at ourselves through the eyes of his Son. Jesus perfectly reveals what God expects. When we look at ourselves through His eyes, we see that, in spite of our sins, God loves us and wants to forgive us. That is why the gospel is good news! Those who accept God's love receive power to conquer sin and be free of guilt. We are authorized to look at ourselves as new persons, as sons of God, and joint heirs with Christ.
No one grasped the implications of this better than the apostle Paul. He was the first person on record to claim to have a "good conscience." (Acts 23:1) He did that while on trial before the Sanhedrin. When he did so, the High Priest — presumably in good conscience — immediately ordered someone to "strike him on the mouth." (Acts 23:2) People have disputed appeals to conscience ever since.
Conflict with the Sanhedrin was inevitable for Paul. He was using a different standard by which to measure conscience. The Sanhedrin measured their consciences by a law that was written by the finger of God on tablets of stone. Paul was measuring his conscience by the Spirit of Christ whose finger he felt clearly on his own heart.
Paul’s dispute with the Sanhedrin should serve as a signal for caution when matters of conscience are being weighed. We will all give an account for what we do with the freedom and power God has given us.
We will all be held personally responsible for every inflammatory opinion we express, for every incendiary action we take, and for every uncharitable vote we make. Those missing or absent when issues of conscience are raised will not escape accountability.
Until that final account is made, each person is required to examine their own conscience. The best way to do that is to measure it by what Jesus revealed that God expects.
That's why Paul says we must appear before the judgment seat of "Christ." It's also the best reason for asking "What would Jesus do?"
When you truly do what Jesus would do, you’ll have a good conscience.
Having a clear conscience, however, is no guarantee that your conscience is good. Some people have a clear conscience when others correctly believe they shouldn't. Another may have a conscience that is clear and good when others incorrectly think he shouldn't.
In the end, we all have to live with our own consciences.
That's why the best we can try to do is strive to have a good conscience.
Ultimately, judging the goodness of consciences belongs to God.