Nearly two decades ago, the "homogeneous unit principle" of church growth entered the vocabulary of the American church. Its disarmingly simple premise: like attracts like. Therefore, Christians will best reach other people who share their essential racial, social, and economic traits.

Countering that idea are those who emphasize the gospel's mandate for reconciliation, not simply growth. Therefore, they urge, people must go beyond racial, economic, and social barriers and learn to worship and fellowship with one another as Christians.

The discussion affects all church leaders, because America is growing ever more diverse. Already, according to Time magazine, "More than 100 languages are spoken in the school systems of New York City, Chicago, Los Angeles, and Fairfax County, Virginia." Time predicts that within sixty years, "the descendants of white Europeans … are likely to slip into minority status."

America is also, to many observers, growing more tense over racial and ethnic issues. ...