14
races from their membership, and there is a church growth principle called the "homogeneous
unit principle" that, if not carefully applied, can encourage such practices.
48
Catholicity in
membership and ministry is also one factor that distinguishes churches from parachurch groups.
While a church as a matter of strategy may target a specific group, and be better equipped in
certain areas of ministry than others, its call still is to catholicity. It cannot exclude anyone
because of age or background It is ecclesiologically invalid for a church to admit only high
school students to its membership, or to minister only in the area of relieving physical needs. It
does not have the option to be like Young Life or World Vision; its missiological boundary calls
upon it to offer all types of ministry to all types of people.
7. The Structural Boundary. While this aspect of ecclesiology is not addressed as
repeatedly or clearly as some other aspects in Scripture and other resources, it still deserves
mention as a part of evangelical ecclesiology. Virtually all evangelicals recognize that the
church is mroe than a mass of people; it has some structural, organizational form. Almost all
denominations have some form of authorized leadership.
49
Almost all recognize the need for
some lines of authority, whether delineated in a congregational, presbyterian, or episcopal
manner. Indeed, a structure with some source of authority (under Christ's headship and ultimate
authority) would seem to be presupposed in the idea of church discipline.
Beyond the bare affirmations of structure and authority, perhaps there is little that could
be said that would apply to all evangelicals. Honest differences in church government have been
a long-standing area of disagreement among evangelicals. But there is at least one pertinent
application. The idea of a divinely given structure and authority in the church provides another
point of distinction between churches and parachurch groups and another reason why those in
parachurch groups need the church. The church is authorized to shepherd believers, to provide
48
For the homogeneous unit idea, see Donald A, McGavran, Understanding Church
Growth (Grand Rapids, MI: Eerdmans, 1970).
49
In On the Councils and the Church, Luther does include the calling of ministers,
bishops, pastors or preachers as one sign or mark of the church. See Luther, Luther's Works, vol.
41, 154.