QUESTION: What is conscience?
ANSWER: We understand "conscience" to be the inward moral sense of good and evil. "To know good and evil" is God's way of describing the acquisition of conscience when man fell (Gen. 3:22). Man naturally, therefore, has a conscience. When merely knowing that what he has done is wrong, he has a defiled conscience (Titus 1:15). When he learns that God judges it to be evil, he has an evil conscience.
When, however, through believing God's testimony concerning the blood of His Son, he is assured by God's Word that he has remission of sins, he has a purged conscience—"How much more shall the blood of Christ, who through the eternal Spirit offered Himself without spot to God, purge your conscience" (Heb. 9:14). After this, in walking in obedience to the Word of God, he has a good conscience, he has the intuitive perception that he is doing God's will and has the testimony that he pleases God. Happy are those who exercise themselves in keeping a conscience void of offense both toward God and toward men (Acts 24:16).
With regard to "thoughts," the Christian needs both watchfulness and decision lest the dreadful sin of unbelief be allowed or Satan's fiery darts admitted. The spiritual Christian disallows evil thoughts, judges them in the presence of God, and thus great evils are often nipped in the bud. One of faith's activities is "casting down imaginations![ reasonings], and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ" (2 Cor. 10:5).