The conscience is defined as that part of the human psyche that induces mental anguish and feelings of guilt when we violate it and feelings of pleasure and well-being when our actions, thoughts and words are in conformity to our value systems. The Greek word translated “conscience” in all New Testament references is suneidēsis, meaning “moral awareness” or “moral consciousness.” The conscience reacts when one’s actions, thoughts, and words conform to, or are contrary to, a standard of right and wrong.
There is no Hebrew term in the Old Testament equivalent to suneidēsis in the New Testament. The lack of a Hebrew word for “conscience” may be due to the Jewish worldview, which was communal rather than individual. The Hebrew considered himself as a member of a covenant community which related corporately to God and His laws, rather than as an individual. In other words, the Hebrew was confident in his own position before God if the Hebrew nation as a whole was in good fellowship with Him.
The New Testament concept of conscience is more individual in nature and involves three major truths. First, conscience is a God-given capacity for human beings to exercise self-evaluation. Paul refers several times to his own conscience being “good” or “clear” (Acts 23:1; 24:16; 1 Corinthians 4:4). Paul examined his own words and deeds and found them to be in accordance with his morals and value system, which were, of course, based on God’s standards. His conscience verified the integrity of his heart.
Second, the New Testament portrays the conscience as a witness to something. Paul says the Gentiles have consciences that bear witness to the presence of the law of God written on their hearts, even though they did not have the Mosaic Law (Romans 2:14–15). He also appeals to his own conscience as a witness that he speaks the truth (Romans 9:1) and that he has conducted himself in holiness and sincerity in his dealings with men (2 Corinthians 1:12). He also says that his conscience tells him his actions are apparent to both God and the witness of other men’s consciences (2 Corinthians 5:11).
Third, the conscience is a servant of the individual’s value system. An immature or weak value system produces a weak conscience, while a fully informed value system produces a strong sense of right and wrong. In the Christian life, one’s conscience can be driven by an inadequate understanding of scriptural truths and can produce feelings of guilt and shame disproportionate to the issues at hand. Maturing in the faith strengthens the conscience.
This last function of the conscience is what Paul addresses in his instructions regarding eating food sacrificed to idols. He makes the case that, since idols are not real gods, it makes no difference if food has been sacrificed to them or not. But some in the Corinthian church were weak in their understanding and believed that such gods really existed. These immature believers were horrified at the thought of eating food sacrificed to the gods, because their consciences were informed by erroneous prejudices and superstitious views. Therefore, Paul encourages those more mature in their understanding not to exercise their freedom to eat if it would cause the consciences of their weaker brothers to condemn their actions. The lesson here is that, if our consciences are clear because of mature faith and understanding, we are not to cause those with weaker consciences to stumble by exercising the freedom that comes with a stronger conscience.
Another reference to conscience in the New Testament is to a conscience that is “seared” or rendered insensitive as though it had been cauterized with a hot iron (1 Timothy 4:1–2). Such a conscience is hardened and calloused, no longer feeling anything. A person with a seared conscience no longer listen to its promptings, and he can sin with abandon, delude himself into thinking all is well with his soul, and treat others insensitively and without compassion.
As Christians, we are to keep our consciences clear by obeying God and keeping our relationship with Him in good standing. We do this by the application of His Word, renewing and softening our hearts continually. We consider those whose consciences are weak, treating them with Christian love and compassion.
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.