According to the Merriam-Webster On-Line dictionary, conscience is defined as:

1 a : the sense or consciousness of the moral goodness or blameworthiness of one’s own conduct, intentions, or character together with a feeling of obligation to do right or be good

1 b : a faculty, power, or principle enjoining good acts

1 c : the part of the superego in psychoanalysis that transmits commands and admonitions to the ego

That is the conscience as the world sees it, but what does the Word of God say about conscience?

Hebrews 10:22  Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water.

The Word of God ties the conscience to the condition of our heart. On September 11^th, 2001, terrorist boarded American Airlines Flight 11, United Airlines Flight 175, crashing into the World Trade Center towers and American Airlines Flight 77, which crashed into the Pentagon. These were acts of an evil conscience. These are extreme examples but reflect the principle that serves to prove a point. The conscience is nothing more than a reflection of the heart. If ones heart is evil, the conscience is also evil and will not exhort you to good deeds.

Luke 11:34 Your eye is the lamp of your body. When your eyes are good, your whole body also is full of light. But when they are bad, your body also is full of darkness.

Do you think those men saw what they were doing as being an evil thing? Their conscience told them what they were doing was good and right, and that they would be rewarded for giving their lives in their cause. A conscience does evil if the heart is evil. The conscience is a function of the mind. It is a reasoning power which weighs character against desire.