When I say the word "church," what comes to mind? A small red brick building with a cross standing high above a steeple, or a large, Gothic, European cathedral? An enormous suburban megachurch or a small but crowded Asian home?

Depending on our cultural context and personal experiences, different images pop in our head when we think about a church, but hopefully we all understand that those buildings are not a church. With such contrasting pictures in our minds, however, how can we tell what truly constitutes a church? That's where ecclesiology comes in.

Ecclesiology, the theological study of the church, is a big theological term, and rightly so. It must bear a great deal of theological weight. What we believe about ecclesiology shapes the way the church is structured, how the people relate to one another, and how it goes about accomplishing its mission.

Historically, ecclesiology has been an important aspect of Christian theology. Every generation has outlined certain distinguishing marks of a church. The Reformers said it was "the right administration of the sacraments" and "the right preaching of the word." Catholics pointed to, among other things, apostolic succession. For 2,000 years, people have been talking about what makes a church a church—until recently.

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Regretfully, the extent of the ecclesiology in most of our churches today is weak. People identify a church simply because it meets and has the word "church" in its name. But beyond that, there is an acute misunderstanding as to how we identify biblical churches.

For the most part, we deem gatherings of people with any inherent focus on Jesus as churches, and that is an unhelpful practice. A church is something to be a church, but our understanding of how that is applied must be both flexible and biblical.

A Flexible Understanding of Church

Contrasted with a biblical mark (or required attribute), there is no one definitive model for a biblical church that can be prescribed as the way to be the church. Churches need to look different according to their cultural context. Flexibility in our ecclesiology is good and necessary, but there is an innate danger in our flexibility, namely, the inability to define or recognize a biblical church.

The church has changed much more rapidly in the last few decades than ever before, and many of the designations we once used to define churches are no longer adequate without additional information.

The labels we use, and in effect, the ways in which we define church, are being reshaped and rethought in innovative ways. Churches are challenging numerous long-held traditional understandings of how we define church.

However, part of the challenge is that some, in their rush to innovate, are often not thinking about God's intention for the church. In Ephesians 3:10, Paul says God has chosen the church to make known His manifold wisdom. The church is the tool, the instrument, the vessel for carrying out God's agenda in the world, but churches frequently make adjustments that do not take that agenda into consideration.

I don't think those pushing past the boundaries have nefarious intentions. They are simply making assumptions about biblical texts instead of thinking through the implications for their churches. We need to address those deficits in our thinking for the sake of God's mission.

You may be asking why it even matters that we have a well-defined ecclesiology. As we engage in church planting, church revitalization or growing and multiplying healthy churches, there is one common factor, one word we see in each of those things that matters—church.

Ed Stetzer, Ph.D., holds the Billy Graham Chair of Church, Mission and Evangelism at Wheaton College and serves as executive director of the Billy Graham Center for Evangelism. He has planted, revitalized and pastored churches, trained pastors and church planters on six continents, holds two master's degrees and two doctorates and has written dozens of articles and books. Read more about Ed at EdStetzer.com.

This article originally appeared at edstetzer.com.

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