The condition of being externally identified with Christianity — born into a Christian family, raised in Christian culture, attending church, affirming Christian values, occasionally reciting Christian prayers — without actual regeneration, living faith, or personal submission to Christ as Lord. The cultural Christian carries Christian vocabulary, Christian ethics in selective areas, and a Christian social identity, but has never truly believed the gospel. Cultural Christianity is the biggest category in nominally-Christian nations: the American churchgoer who is "Christian like I'm Irish," the European whose baptism and Christmas attendance mark a heritage but not a new birth.
Cultural Christianity is the single greatest mission field inside nominally-Christian nations. Several implications. (1) It is a false assurance. Being raised in a Christian home, baptized, catechized, and comfortable at church are no guarantee of saving faith. Jesus said to Nicodemus — a Pharisee of Pharisees, the most cultural-religious man imaginable — "you must be born again" (John 3:7). (2) It is often harder to reach than pagan unbelief. A pagan knows he is outside the faith; the cultural Christian is inoculated against the gospel by the small dose of Christianity he has received. He thinks he already has what he lacks. The Pharisees who crucified Jesus were cultural Judaism of the highest grade; the Samaritans, pagans, Gentiles, and sinners welcomed the gospel more readily. (3) It should not be mocked or written off. Some cultural value in a Christian-influenced society is better than none — laws protecting the unborn, marriage, and religious liberty; charitable tradition; ethical instincts about honesty and generosity — these are common-grace benefits of a Christianized culture. Tom Holland's Dominion argues the whole Western moral vocabulary is downstream of Christianity. Defend these. But cultural Christianity is not the gospel and will not save anyone. It must always be pressed toward personal faith in the crucified and risen Christ. The cultural Christian is closer geographically but no closer spiritually than the atheist; both need conversion.