Built into our nature is an internal judicial system, the conscience, that commends us when we do right and condemns us when we do wrong. But this vital monitor of morality does not say the same thing to everyone. In some cultures vengeful killing is seen as honorable. In others, a person is still considered good even when he betrays a friend.
A story from The Philadelphia Inquirer illustrates this problem. A 12-year-old boy was caught stealing a watch. He told police that previously he had shoplifted a gift for his mother, and he felt he had to do the same for his dad. Although troubled about slighting his father, he had no qualms about stealing.
Because of sin, conscience is unreliable and needs a continual adjustment. This begins with a right relationship to God through faith in Jesus Christ. He paid sin’s penalty, and now our hearts are “sprinkled from an evil conscience” (Heb. 10:22). But this does not make conscience obsolete. As we study the Scriptures, the Holy Spirit puts our inner monitor on a frequency that brings us in tune with the words, deeds, and attitudes of the Lord Jesus.
“Let your conscience be your guide” is valid only if God’s Word is guiding your conscience.
There is a treasure you can own
That's greater than a crown or throne:
A conscience good with which to live,
That only God Himself can give. —Isenhour
Conscience is like a sundial: when the truth of God shines on it, it points in the right direction.