Martin Luther was once approached by a working man who wanted to know how he could serve the Lord. Luther asked him, "What is your work now?" The man replied, "I'm a shoemaker."
Much to the cobbler's surprise, Luther replied, "Then make a good shoe and sell it at a fair price."
He didn't tell the man to make "Christian shoes." He didn't tell him to leave his shoes and become a monk.
As Christians, we can serve God in a variety of vocations. And we don't need to justify that work, whatever it is, in terms of its "spiritual" value or evangelistic usefulness. We simply exercise whatever our calling is with new God-glorifying motives, goals, and standards.
Outwardly there may be no discernible difference between a non-Christian's work and that of a Christian. A transformational approach to culture doesn't mean every human activity practiced by a Christian (designing computers, repairing cars, selling insurance, or driving a bus) must be obviously and externally different from the same activities practiced by non-Christians.
Rather, the difference is found in the motive, goal, and standard. John Frame writes, "The Christian seeks to change his tires to the glory of God and the non-Christian does not. But that's a difference that couldn't be captured in a photograph."
So, while Christians are to separate from the self-glorifying motives and God-ignoring goals of the world (our spiritual separation), we're not to separate from the peoples, places, and things in the world (a spatial separation). We're to be morally and spiritually distinct without being culturally segregated. In the famous words of Abraham Kuyper, "There is not one square inch in the entire domain of our human existence over which Christ, who is Sovereign over all, does not cry, 'Mine!'"
For church leaders, this means that we make a huge mistake when we define a person's "call" in terms of participation inside the church—nursery work, Sunday school teacher, youth worker, music leader, and so on. We need to help our people see that their calling is much bigger than how much time they put into church matters. By reducing the notion of calling to the exercise of spiritual gifts inside the church, we fail to help our people see that calling involves everything we are and everything we do—both inside and, more importantly, outside the church.
I once heard Os Guinness address a question about why the church in the late 20th century was not having a larger impact in our world when there were more people going to church than ever before. He said the main reason was not that Christians weren't where they should be. There are plenty of artists, lawyers, doctors, and business owners that are Christians. Rather, the main reason is that Christians aren't who they should be right where they are.
"Calling", he said, "is the truth that God calls us to himself so decisively that everything we are, everything we do, and everything we have is invested with a special devotion, dynamism, and direction." When we reduce the notion of "calling" to work inside the church, we fail to equip our people to apply their Christian faith to everything they do, everywhere they are.
As has often been said, "If Christ is not Lord of all, he's not Lord at all."
Because God created peoples, places, and things, and because sin has corrupted peoples, places, and things, God intends to redeem people and their cultural sphere. In Christ, God intends to redeem not only environmentalists but also the environment; not just lawyers but also law; not simply government officials but also government itself (Isa. 9:6-7).