I've been struck a few times in the last few days with the role of the conscience for preaching and evangelism. Most recently I found a helpful section in Russ Moore's article "The Child Not Taken" in the current issue of Touchstone Magazine.
Moore writes, "For the unbeliever, the conscience is not Disney's Jiminy Cricket, offering a friendly, understanding, welcome guide. Instead, it is a universal gnawing within the heart that points to a coming judgment, which men and women desperately want to deny exists at all. It is found everywhere, in all people in all places at all times--and it is always smothered by people who do not want to hear its voice."
"This is the Achilles' heel of so much of our preaching and witness. Some of us try to reach the culture by offering 'life principles,' twelve steps to personal peace and so forth. Some of us try to offer rigidly organized doctrinal explanations of Christianity. Some of us (though far fewer) try to scare unbelievers into thinking aobut how miserable hell will be. None of these is the way the apostles preached."
"Jesus said that through the gospel the Spirit 'convicts the world of sin and righteousness and judgment.' Paul said that his preaching explicitly appealed to the consciences of his hearers. These consciences are 'seared' by years of self-justification, but it is the forthright proclamation of the gospel that pierces through this satanic deception."
Though you can only read the rest of this article in Touchstone Magazine, you can read more of Moore at The Carl F.H. Henry Instutute for Evangelical Engagement.