The Greek word for church [ekklesia] means “the called-out ones.” The Church as an assembly of people called by God.
The church does not always reflect what its name implies. Jesus said the church in this world is made up of a combination of wheat and tares, and while the church is called to pursue purity, Christ warned against overzealous church discipline that, in seeking to root out the tares, might do harm to the wheat (Matthew 13:24-30).
THE INVISIBLE AND VISIBLE CHURCH
The term invisible church refers to those who are true believers. By contrast, the visible church is the body of all who claim to believe in Jesus and who identify with the church. The invisible church is so-called, because we are not able to see a person’s heart. We can evaluate a person’s profession of faith and commitment to Christ only on the basis of outward appearances. If someone tells me he is a Christian, I must assume he is telling the truth.
We must avoid the assumption that the invisible church and the visible church are separate entities. As Augustine observed, the invisible church is found substantially within the visible church. Thus, the invisible church is made up of true believers within the visible church.
There are a variety of reasons why some believers are not members of the visible church. Sometimes a believer is providentially hindered from joining a visible church. He might, for example, become a believer but die before he ever has a chance to join a church. Such was the case with the repentant thief on the cross. Some have never been taught the importance of belonging to a church. Some are frustrated with the institutional church. However, if anyone learns he is required to be in a church (Hebrews 13:17) but persists in remaining outside, we can rightly question whether that person is really a Christian.
Some Christians do not belong to a visible church because they have been excommunicated – the final step in the process of church discipline. Theoretically, true Christians can fall into sin and persist in it throughout the process of church discipline, such that the only thing that brings them to their senses is excommunication. This is the very purpose of excommunication.
The church was not started in the New Testament (Acts 7:38). It has its roots all the way back to the Garden of Eden. Adam and Eve, in the direct worship they offered their Creator, were the church. Wherever we find people who trust God for their salvation through Christ (or, in the case of the Old Testament saints, the promise of Christ), there we find the church.
[Adapted from R.C. Sproul, Everyone’s a Theologian]