This is a question that I have been thinking about much on this afternoon. The main reason being that some involved in our church plant have been challenged by long time "churchgoers" that they aren't going to a "real church." The reasoning behind this charge is that we do not have a building and have begun meeting in homes until we are ready to secure a more permanent meeting facility. But what about churches that never move out of homes? Are the home churches in China not churches? And what about passages like Romans 16:5 which clearly teach that churches in the New Testament did in fact meet in homes (they had to because they didn't own any property as churches). The mindset that ties the church to a building is a troubling one indeed. I don't care how often people in church say, "The church isn't a building, it's people," the message we are sending to an unbelieving world often contradicts this truth we claim to hold to.
What would the average unchurched person say if you were to ask them what makes someone a Christian? In there answers, perhaps the first thing our of their lips, you will hear "you go to church." Yes, part of this is due to the fact that unbelievers do not have the Holy Spirit and cannot discern biblical truth on their own. However, could it be that the reason they think this is because "church people" rarely tell them about Jesus, but are constantly "inviting them to church?" When I talk to adults who have grown kids who have left the faith they usually say something like "they just need to get back into church." No, they need to repent and believe in Jesus. As Keith Green used to say, "Going to church doesn't make you a Christian any more than going to McDonald's makes you a hamburger." So what is a church? The Reformers had a good answer to this as they presented three marks of a true church.
First, a true church has the mark of the proper administration of the Word of God. Paul commands Timothy to "Preach the Word!" This does not mean that at some point during the meeting a Bible verse is read. This does not mean that some jack-leg preacher reads a text and then says whatever he wants to say, pretending that he is preaching a biblical message. This does not mean that you preach the Bible as moralism or as me-centeredness (I previously linked a great article by J.D. Greear on this topic). Rather, it means that not only does the preacher preach the text, but the text is what preaches itself. The pastor is to allow the sermon dictate the text, not the other way around. Every text has one main point. In fact, the Bible has a main point. Every passage in the Bible points to the person and work of Jesus Christ. This is what the Bible is about and He is what is to be preached week in and week out.
Second, a true church has the mark of the proper administration of the ordinances. There are two ordinances that must be practiced regularly and properly in order for a church to be a church, they are Baptism and the Lord's Supper. Both were commanded by our Lord and are essential in the life of the church. The Bible is clear that all believers are to be baptized, it does not mandate how often we should celebrate the Lord's Supper. It does seem that many churches aren't celebrating the Lord's Table whenever they can but as least often as they can. Many home churches partake of the Lord's Supper every Sunday while many "churches" with buildings only celebrate (if you can call it that) communion quarterly or even less (one church I know only takes it every fifth Sunday, which relegates the sacred event to the level of a honky tonk gospel sing).
Third, a true church has the mark of church discipline as given by Jesus in Matthew 18. This disqualifies at least 90% of American churches as being churches! We don't take sin seriously. A church cannot be a church with that kind of mentality.
Notice their is no mark that includes having a building or an organ or a budget. None of these things are wrong in and of themselves, but they aren't essential in making you a church. We need to think biblically about the church. It is not the church that decides what a church is, it is the teaching of the Bible.