This English term is related to the Latin conscientia, literally, "to know together" or "joint knowledge." It corresponds to the Greek suneidesis (found thirty times in the New Testament), which essentially has the same meaning.
The conscience is an inward faculty, unique to human beings, that either accuses or excuses a person's thoughts, words, and actions (Rom. 2:15). The conscience does not determine what is right or wrong (Prov. 14:12; Acts 23:1), but merely recognizes guilt based upon the standard of conduct adopted by the individual.
Divine revelation (the Scriptures) must educate and cultivate the conscience to remain sensitive to truth (Eph. 4:19; 1 Tim. 4:2; Heb. 5:14). Because the conscience is a very sensitive instrument, it is wrong to violate it even in matters of expediency (Rom. 14:23).
Peter indicates that when one surrenders to the gospel plan of salvation (particularly in the culminating act of baptism), he is appealing to God for a clear conscience (1 Pet. 3:21 ASVfn), which is cleansed ultimately by the blood of Christ (Heb. 9:14).