THE PRACTICE OF UNITY
Having established that racial and social unity is the theological ideal that should be manifested in the Church, we are still left with the thorny question of how to most effectively and edifyingly put into practice this ideal in the everyday contexts in which missionary and local church ministry take place.
When faced with the reality of the global church, it is tempting to accept homogeneous churches as an inescapable element of the evangelical landscape. As Wagner observes, “There is no question that the vast majority of the world’s Christian churches are culturally homogeneous. If the exact data were available, I would not be surprised if they showed that something on the magnitude of 95 to 98 percent of the congregations in Christendom are made up basically of one kind of people.”  Even in a place as culturally diverse as the United States, “According to the 1998 National Congregations Study, about 90 percent of American congregations are made up of at least 90 percent of people of the same race.”  And yet, due in great part, no doubt, to the theological reasons presented in this paper, Schnabel observes, “The popularity of the ‘people group principle’ is waning among missiologists.” 
At the same time, however, a sincere desire for gospel faithfulness and effectiveness in the evangelistic task given by Jesus to his disciples has led many to seek practical handles for the carrying out of their missionary ministry by way of church growth principles and a focus on reaching the unreached people groups of the world for Christ. There is, undoubtedly, some degree of legitimacy behind this focus. The example of Jesus as the Good Shepherd who came to “seek and to save the lost” (Luke 19:10) and who leaves the ninety-nine sheep in the fold in order to seek out the one that was lost (Luke 15:1–7) is surely instructive to us as his followers who have been sent with the same mission, just as he was sent by his Father (John 20:21). We are to “go to the street corners and invite to the banquet anyone [we] find” to come to the feast he has prepared (Matthew 22:1–14). Most assuredly, there is a message here concerning the imperative to penetrate cultural, social, and linguistic barriers in order to seek out the “hidden peoples” of the world, doing our best to make sure every individual has the opportunity to hear the gospel message in a way that makes sense to them and inviting them to form part of the people of God.
If our evangelistic methods are placing unbiblical barriers in front of people becoming faithful disciples of Jesus, we must do what we can to eliminate these barriers. It is at this point that a focus on people groups has some important missiological value. As Schnabel affirms,
The sociological focus of the church-growth movement is certainly helpful in one respect. It challenges churches to analyze and study the various social groups and subgroups that live in the city, region, province and country. A local church should know which social groups their members belong to, which social groups are underrepresented and which social groups are totally ignored. As the pastors and teachers of the church seek to preach the whole counsel of God, they want to reach all people who are willing to listen to the news of Jesus. They do not want to reach only Jews or only Greeks but both Jews and Greeks, not only slaves or only the free but both slaves and free, not only men or only women but both men and women. 
We may conclude that a “people group” approach has positive value when used as a tool for opening doors for the inclusion of more and more people into the realm of God’s kingdom, but can have negative consequences when used for excluding people from full fellowship with other members of the Body of Christ.
The Need for Understandable Gospel Communication
An overriding principle governing this process is the need to make the communication of the gospel as comprehensible as possible. An obvious application of this principle has to do with language differences. If the gospel is going to be clearly communicated, it must be communicated in a language that is understandable to the hearers. While on the Day of Pentecost each of the hearers was miraculously enabled to understand the messages spoken in tongues by the disciples of Jesus , the norm for modern-day missions is an intentional and concerted effort on the part of the proclaimers of the gospel to learn the languages of the hearers and to present the message in a way that is comprehensible to them.
While with some degree of effort, through the use of interpreters, bilingual (and even trilingual) gospel meetings and worship services are a viable option, in many settings a truly multilingual meeting that reflects the full linguistic diversity of the surrounding community would only result in cacophony. For this reason, it would appear that the presence of linguistic differences, in at least some cases, is a sufficient motive for justifying some degree of homogeneity along language lines. 
By the same token, the case can be made that not only language but also cultural differences can in various ways obstruct the accurate hearing of the gospel message. Cornett and Edwards argue that differences in worldview can present a major obstacle for clear communication, and may thus form one legitimate reason for homogeneous unit churches.  It is due to this factor that missiologists have long pointed to the need to contextualize the proclamation of the gospel in a way that is meaningful and relevant for those to whom it is being proclaimed. While this is undeniably true, it is also true that biblically faithful contextualization must not in any way obscure or distort the transcultural, universally valid essence of the gospel message being communicated. Correspondingly, if (as has been argued above) the message of racial and social reconciliation is a non-optional core element of the gospel, it must be asked in each case to what extent an intentional segregation of gospel hearers and worshipers facilitates a correct understanding of the gospel and/or simultaneously obstructs a correct understanding of the gospel.
HUP Dynamics Around the World
McGavran maintains that the HUP is universally applicable in whatever context of the world one might find oneself.  While the human tendency toward ethnocentrism may indeed be universal, it is much more difficult to demonstrate that the use of the HUP as a missiological principle has produced universally positive consequences.
One interesting case in point is that of the country of Rwanda. Before the violent uprisings and tragic massacres of 1994 in which between 500,000 and 1,000,000 Tutsis and Hutus lost their lives, Rwanda was held up by both McGavran and Wagner as a prime example of the positive effects of the missiological use of the HUP.  Due to an “effective” Christianization of the various people groups present in Rwanda along ethnic lines, an unusually high percentage of the population claimed at least nominal adherence to Christianity at large and membership in one church or another. When asked several years after the genocide to reflect on lessons learned as a result of the tragedy, however, evangelical statesman Tokunboh Adeyemo wrote that, among other lessons, “The church must seek unity. There must be neither Jews nor Greeks (no racism, tribalism, or sexism). There must be neither bond nor free. Homogeneous church growth formulas, like the old missionary comity arrangements, should be discouraged. Such methods only reinforce tribalism.” 
The United States
The North American context, drastically different in many aspects from that of Rwanda, provides another interesting case for study. The history of racial conflict, especially between blacks and whites, in the United States is well-documented. Indeed, because of this history, in certain circles racial reconciliation between blacks and whites in the United States has become the cause célèbre for the church at large. Such an emotionally charged atmosphere has led Wagner to remark that “Christian opposition to the homogeneous unit principle in America derives more from American civil religion than from purely biblical or theological sources.” 
The fact of the matter, however, is there are certain elements of popular religion in the West, manifested in a particularly noteworthy fashion in the United States, that have favored the development of a peculiar expression of homogeneity among Christian churches. These elements may perhaps best be described by the term “consumerism.”  It appears that the consumeristic mindset representative of American society at large has made inroads among the church in the form of congregational “niche marketing” designed to attract a “clientele” matching up with a certain “demographic profile.” This mentality has produced such ecclesiological novelties as “cowboy churches,” “drive-in churches,” “youth churches,” and “seeker churches,” not to mention the thousands of other garden-variety homogeneous unit churches dotting the American ecclesiastic landscape.
In an interesting turn of events, it appears that this approach to church is making a bigger impact in the Global South than in Europe. Tom Zimmerman makes the following observation: “The limited usefulness of the homogeneous unit principle in Europe is also clear. Rarely are there enough interested people from one target group to start a thriving evangelical church. Many of the existing churches purposely choose to avoid homogeneity, so that they can appeal to a broader spectrum of society.”  On the other hand, Mark Noll, in his book The New Shape of World Christianity, documents how the exportation of much of the American approach to religion, including consumeristic Christianity, has in recent years played a major role in the spectacular growth of the church in the Global South. 
The Muslim World
Writing from a Muslim context, David W. Shenk observes that the relative lack of ethnic loyalties on the part of certain people from Muslim backgrounds and a desire to be more individualistic in their outlook has made them more open to Christianity in general, and more particularly to churches that provide “a primary fellowship which is also genuinely universal, and . . . affirm the integrity of personhood.”  Similarly, he references certain contexts in East Africa where the use of Swahili in place of more ethnically specific tribal languages as well as a transethnic and transcultural approach to church has proven to be a positive factor for numerical church growth.” 
Rural Areas and Isolated Tribal Groups
An additional situation that calls for a unique perspective is that of rural areas and/or isolated tribal groups in which the surrounding community is composed of only one racial group. In such a setting, a de facto practice of the HUP on a local basis is practically inevitable and need not be discouraged. On the other hand, this particular circumstance should not be allowed to become an excuse for exclusivistic racism or intentional isolation from the broader Body of Christ, whenever opportunities for wider fellowship present themselves. 
A final case in point that some have claimed warrants exceptional treatment is that of immigrant populations. DeYoung et al., for example, regard the “unique circumstances of first-generation immigrant groups” as one of the few exceptional justifications for homogeneous unit churches.  While in certain situations, especially where there are language barriers present, this proviso may well be valid, in my personal experience, I have not always found this to be the case. During my missionary experience in Spain in the 1990’s and 2000’s a flood of immigrants from Spanish-speaking countries in Latin America led to a concurrent growth of many pre-existing evangelical churches as well as the establishment of new congregations comprised almost exclusively of homogeneous groups of newly arrived immigrants. Though the adjustments were often difficult, both for the long-time Spanish believers as well as the newly arrived immigrants, several congregations with which I am acquainted were able to successfully integrate large groups of immigrants, bringing a special blessing that included both numerical and spiritual growth on the part of many, as well as a golden opportunity to bear witness to the reconciling power of the cross of Christ in the surrounding community.
 Wagner, “How Ethical Is the Homogeneous Unit Principle?,” 12.
 Michael O. Emerson and Christian Smith, Divided by Faith (Oxford: Oxford University Press, 2000), 135–36.
 Schnabel, Paul the Missionary, 405–06.
 Ibid., 413.
 Though some interpreters understand the biblical narrative as indicating a miracle of understandable hearing on the part of the hearers, and others a miracle of understandable speech on the part of the speakers, the point is moot with regard to the present discussion. Apart from an obvious miracle on the part of God, clear gospel communication in a multilingual setting requires gospel communicators to learn the languages of the hearers and defer to them in their presentation of the gospel.
 Ortiz, One New People, 37.
 Terry Cornett and Robert Edwards, “When Is a Homogeneous Church Legitimate?,” EMQ 20, no. 1 (January 1984): 24.
 McGavran, The Bridges of God, 161.
 Ibid., 6–7. C. Peter Wagner, Your Church Can Grow (Glendale, Ariz.: Regal, 1976), 128; Wagner, Our Kind of People, 11.
 Tokunboh Adeyemo, “Lessons on Rwanda for the Church in Africa,” EMQ 33, no. 4 (October 1997): 430.
 Wagner, Our Kind of People, 53.
 Emerson and Smith, Divided by Faith, 136–37, 140; DeYoung et al., United by Faith, 133.
 Tom Zimmerman, “Willow Creek or Lima? Europe’s Church Planters Ask,” EMQ 27, no. 4 (October 1991): 398.
 Mark A Noll, The New Shape of World Christianity: How American Experience Reflects Global Faith (Downers Grove, Ill.: IVP Academic, 2009).
 David W. Shenk, “The Muslim Umma and the Growth of the Church,” in Exploring Church Growth (ed. Wilbert R. Shenk; Grand Rapids: Eerdmans, 1983), 152.
 Ibid., 151–52.
 DeYoung et al., United by Faith, 143. See also Sidney H. Rooy, “A Theology of Humankind,” in Exploring Church Growth (ed. Wilbert R. Shenk; Grand Rapids: Eerdmans, 1983), 203–04.
 DeYoung et al., United by Faith, 143.