We find that, in the Apostle's time, there were characters who held faith, or rather what they called faith, and put away "good conscience." He mentions by name, "Hymeneus and Alexander, whom he had delivered unto Satan," that is, excommunicated them out of the Church, as heretics and blasphemers. But if to have put good conscience away, stamps a man as unfit for the visible Church of God, it behoves us to search whether we have this weapon at our side, and in our hand.
What does the Apostle, then, mean by "a good conscience?" I believe he means a conscience alive in God's fear, a spiritual conscience, a tender conscience, what he calls, in another part, "a pure conscience;" "holding faith in a pure conscience," that is, purified from ignorance, from guilt, from the power of sin, "a conscience void of offence toward God and men." Wherever, then, there is living faith in the soul, there will be united with it "a good conscience." The Lord never sends forth a soldier to fight his battles with the weapon of faith only; he puts faith in one hand and "a good conscience" in the other. And he that goes forth with what he thinks to be faith, and casts aside "a good conscience," will manifest himself to be one of those characters, who, "concerning faith make shipwreck."
But why is it called "a good conscience?" Because it comes down from God, who is the Author of all good, the Giver of "every good gift, and every perfect gift." There is none good but he, and there is nothing good but what he himself implants and communicates. This weapon of a good conscience, that the Lord arms his soldiers with, works with faith, as well as proves the sincerity of faith, and tests its genuineness and reality. Faith, without a good conscience, is dead. It bears upon it the mark of nature, and however high it may rise in confidence, or however it may seem to abound in good works, it is not the faith of God's elect, of which the end is the salvation of the soul.
But it may be asked, How does a good conscience work with faith? What is the connection between these two weapons, and how do they mutually support and strengthen each other? In this way. What faith believes, good conscience feels; what faith receives, good conscience holds; what faith embraces, good conscience rivets fast; when faith is weak, good conscience is feeble; and when faith is strong, good conscience is active. They grow and they wane together, and like two stems from one root together do they flourish and fade. He then alone wars the good warfare, who goes forth with faith in the one hand, and "good conscience" in the other; faith strengthening conscience, and conscience strengthening faith; each doing their separate office, but still tending to one end; each accomplishing the work which the Lord has appointed, and yet each fighting the Lord's battles, and bringing the soldier safe and victorious over his enemy.