I cannot recommend the works of John Flavel enough. He is simply brilliant. Below is an excerpt from a forty page appendix, if you can believe it, to a treatise he wrote on England’s Duty. This appendix is, again, forty pages commenting on Romans 1:18. He delves into the purpose of the conscience and its function as the divine ethical compass. I think we could throw in John 1:9 as more backup to his talk here. I’ve never liked the statement, “Let your conscience be your guide” mainly because the definition of the conscience seems to have evolved into “follow your heart” or “do what makes you happy” because if your happy, then you must have a clear conscience, right?
Well, Flavel is very helpful here. And in true Puritan style, he looks at the conscience as that part of man, made by God, to point man to God, and his law, which is in itself, God’s self-revelation. Here’s Flavel:
Conscience, therefore, is a high and awful power, it is…next and immediately under God, our judge; riding, as Joseph did in the second chariot. And concerning conscience, he saith to every man, as he did to Moses, with respect to Pharaoh, See, I have made thee a god to Pharaoh, Exod. 7:1. The voice of conscience is the voice of God. What it bindeth or looseth on earth,…, is accordingly bound or loosed in heaven, 1 John 3:21. The greatest difference and precise obedience is due to its command. Its consolations are, of all, the most sweet, and its condemnations (only excepting those by the mouth of Christ in the last judgement) most terrible.
Zuinglius spake not without ground, when he said, “What death would I not rather chuse? What punishment would I not rather bear? Yea, into what a profound abyss of hell would I not rather enter, than to witness against my conscience?” It is like he had felt the terrors of it to be more bitter than death. How many have chosen strangling, rather than life, under the terrors of conscience? Wherever you go, conscience accompanies you; whatever you say, do, or but think, it registers and records, in order to the day of account.
When all friends forsake thee, yea, when thy soul forsakes thy body, conscience will not, cannot forsake thee. When thy body is weakest and dullest, thy conscience is most vigorous and active. Never more life in the conscience than when death makes its nearest approach to the body. When it smiles, cheers, acquits and comforts, oh, what a heaven it doth create within a man! And when it frowns, condemns, and terrifies, how doth it becloud, yea, benight all the pleasures, joy, and delights of this world?
O Conscience! how glad would the damned be to have taken their last farewell of thee, when they bid this world and all its inhabitants farewell, at death! And what had become of all the sufferers and martyrs, when shut up from friends in dungeons, had it not been for the cheering cordials and comforts thou there administered to support them!
It is certainly the best of friends, or the worst of enemies in the whole creation. This is conscience, these are its powers and offices………
– John Flavel, works vol. 3, page 272, Banner of Truth