The unrenewed man does not oppose sin out of a hatred for it as sin, so his opposition is only levelled against some sins, specially the gross and scandalous sins, those that are infamous or contrary to moral honesty, or his natural disposition. A natural conscience will tremble at murder consummated, but not at every degree of it, not at secret inward sins, nor at the first motions of sin, not at lucrative sins, and such as a profane age has made an vulgarly made honourable. And especially not at unbelief. It is true, a natural man may be sensible of the sin of his thoughts, of inward disorders, conviction, disturbance, or led to something that abhors. But, it’s not with every degree of sin, with unbelief that keeps him out of heaven. It is not for the sinfulness of the motions of these sins, he sees them as the disease of nature, not his sin. He may be displeased with the stirring of sins, but not with the root of them. If he can restrain the acts, he will be contented. But with the godly it is different, for sin opposes every gracious act, so grace opposes every known sin, and does so secretly, though we may not always be sensible of it. Grace in the heart, feels that to be sin, and contrary to its nature, which knowledge in the head doesn’t discern to be sin (the law written in the heart, always goes further than what’s in the head), like eating what one dislikes will trouble us, though we may not know we dislike it, but more so if we eat it.