I've always been very intrigued by Jesus's words from the Sermon on the Mount, " Let your light shine before men, that they may see your good deeds and praise your Father in heaven." I take Jesus to mean what he says, which means here that our actions/behaviour cause the world to turn to God and praise Him. Now, I guess we would normally say that it is very important that Christians live holy lives that validate the preaching of the gospel. Yet, it seems here that it is the actions themselves that cause the faith/praising in others. The actions themselves are a form of preaching.
Now, what kind of actions are these? It would seem to me they must be actions that are so unusual, so unique, so different, that onlookers must say as a result "wow, this can only be explained by there being a God and this God working among them." This is not just Christians being nice and good. This behaviour must be beyoned ordinary, natural explanation - otherwise unbelievers would not be convicted into praising God. This is unnatural virtue - or supernatural virtue.
What might this be? Well, we find out in the Sermon on the Mount itself. It is love for enemies. It is real forgiveness. It is the courage to take a slap and be mistreated for love. It is the life of the beatitudes and of mercy. These things cannot be explained in any ordinary kind of a way. There is something unworldly about them. This is not natural virtue found simply because we're made in the image of God. It is behaviour that has a gospel shape to it. It reveals extraordinary grace to a world that lives by works righteousness. It is so extraordinary that it preaches the reality of God and the gospel. It causes people to praise God for my life!
I am in no way saying we do not need cogent, clear, powerful preaching of the word, nor am I saying our lives are a replacement for preaching the word, but it would seem to me that we also need cogent, clear, powerful preaching of Christ's grace through our character. And it also seems that we should not underestimate the power of our character to preach the grace and mercy of God. Of course, that will happen only when we demonstrate extraordinary character shaped by extraordinary grace.