The last thing a soul has to give up, when seeking salvation or sanctification, is "an evil heart of unbelief" (Heb. iii. 12). This is Satan's stronghold. You may drive him from all his outposts and he does not care much, but when you assail this citadel he will resist with all the lies and cunning he can command. He does not care much if people do give up outward sin. A respectable sinner will suit his purpose quite as well as the most disreputable.
