Two related habits of thought will render a Christian useless to his neighbors more quickly than just about any others. The first is the idea that our blessed hope is a disembodied existence strumming harps on clouds somewhere East of Mount Olympus for eternity. “This world is not my home, I’m just a’passing through,” as Jim Reeves sang. The other is that Christians are not citizens of this world in any moral sense, but live by an alien law from a different city.

I don’t mean this in the way Augustine did. His “city of man,” which was founded when Adam ate the fruit and established when Cain fled with the blood of his brother on his hands, has always been at war with the City of God. I am talking about a view that identifies the city of man with everything that is not the Church. In this view, anything not explicitly Christian becomes suspect, and our non-Christian neighbors are seen as moral cripples incapable of walking any road but Romans.

Anyone who is in the business of “engaging the culture” has either encountered this habit of thought or will very soon. There’s an obvious tension between any effort to restore and redeem our shared public life with unbelievers and the notion that unbelievers are incompetent for that shared public life. After all, what’s the use in trying to influence government, commerce, the academy, medicine, or entertainment for good if no one is going to understand what “good” means until they’ve given their lives to Jesus? In that case, we should be preaching the Gospel, not engaging the culture!

When morality becomes the exclusive province of Christians and Christianity, it collapses our mission in this world to evangelism, and turns all our efforts at good citizenship into a branding exercise. It leaves us with a Christian way of living and a non-Christian way of living, and nary the twain shall meet.

Depending on their personality and zip-code, believers who accept the idea that Jesus came to found a revolutionary new way of life alien to this world will adopt one of two postures. Either they will cordon off most of life as “secular” or “public,” and reserve a little private corner for their religion and its moral beliefs, or they will declare all of life sacred and go about attempting to set up a theocracy on their block. I’ll tackle the second group, first.

You’ve probably read a book or article in which the author so emphasized the unique contribution of Christianity in the world (for instance, in ending infanticide, elevating the status of women, or giving rise to the concept of human rights), that he or she leaves the impression that Christianity invented right and wrong. Those who want to emphasize how good Christ’s religion is for the world (and it is!) often come dangerously close to denying Paul’s teaching in Romans 1-2 that all of mankind has access to a culpable knowledge of God and the requirements of His moral law. For them, the Greeks and Romans weren’t exposing baby girls in defiance of a universal and natural law against murder, which they were suppressing. They simply had not received word from Jesus that baby-killing is wrong! Thus, Christianity becomes a replacement for nature, an ethical gnosis confined to the enlightened, a higher plane of existence—rather than the grace to restore the nature God put in His world at creation.

Then there are the apologetic battering rams, the type who use Van Tillian siege engines to tear down unbelievers’ pretensions of having any right to talk about good, evil, truth, or falsehood. “By what standard?” they demand of agnostics who think Christians are jerks for not baking gay-wedding cakes. The unbeliever often doesn’t have a very good answer, it’s true. That’s why the question keeps getting asked. And the apologist may come away from the exchange looking clever. But in my experience, the end result is rarely an unbeliever on his knees before the presuppositional kung fu master, asking “what must I do to be saved?”  It’s usually an unbeliever who thinks of Christians from then on as high-strung con artists who won’t level with you and talk about the real world until you’re baptized.

Then there are the timid sorts, the ones I mentioned earlier who rope off a little nook of their lives for Christian standards and live everywhere else as if Bill Maher is lord. You will hear these Christians talk about their religious beliefs as “deeply personal” and they will frequently mention that Sunday school class they taught or how they were altar boys, before they pivot to the separation of church and state and assure all within earshot that they’re not interested in imposing their beliefs on anyone, goodness gracious! You will often find them berating fellow Christians in blog posts, reminding us that we mustn’t hold the lost to a “Christian” standard, as if not dismembering children or engaging in same-sex relations were moral revelations given during the Sermon on the Mount. These incognito believers are especially common in my generation, who are quick (you have no idea) to explain that although they’re personally pro-life and think marriage in the church is between a man and a woman, they also accept a woman’s right to control her own body and are glad their gay friends can get married.

At first glance, these stealth Christians may seem like the opposite of the moral revolutionaries and the battering rams, but they actually share the foundational belief that “Christian morality” is a supernatural revelation that has little to do with those who don’t share our religion. For all three of these camps, our job as the Church isn’t really to persuade our neighbors of an ethical position or to write just laws, or to promote human flourishing, or even to be good citizens in general, but to overhaul worldviews. It’s useless to try to convince pagans of Christian standards of behavior, this thinking goes, because such standards are foreign to them, blossoming as they do in the soil of beliefs revealed by Scripture—beliefs which no one can share until they submit to Christ. The real problem, say proponents of “Christian morality,” is upstream from opinions on babies and bedposts. They all see conversion as a prerequisite for discussions about right and wrong. The only thing they disagree on is how Jesus and Bill Maher will divvy up jurisdictions.

But what if morality doesn’t need a modifier? What if serious discussion of right and wrong is not the exclusive domain of religion, but part of living in this world? What if Jesus came not to introduce a new way of life, but to restore God’s original and good design, which has been broken?  And what if this distinction makes Christianity more relevant to the world, not less?

One thing is certain: If morality is uniquely Christian, then “engaging the culture” is a fool’s errand. Jerusalem has nothing to do with Athens, or any other city, for that matter. But if right and wrong are intelligible concepts to the unbeliever—concepts the unbeliever is responsible for ignoring—and if there are natural reasons why marriage has a definition, why killing unborn children should be illegal, why boys cannot become girls, and why people should not be forced to say things they don’t believe, then Christians have something to do with this world. We are its moral citizens by birth, and its best citizens by rebirth. And we are here not only to announce that God is repairing human nature. We’re here to demonstrate what that looks like.