However, there is another reason why the unity of the church is a serious imperative for us that I have not so often heard discussed. (Perhaps this is simply because I have not been listening to the right conversation; but, nevertheless, from what I have heard I think this issue deserves greater emphasis.) That reason is the connection between the unity of the church and the success of the mission of the church to evangelize the nations.
Christ has commanded his people to "go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost, teaching them to observe all things whatsoever I have commanded you" (Matthew 28:19-20). And he has promised that in doing so "I am with you always, even unto the end of the world." The Scriptures promise that the preaching of the gospel will be accompanied with success. The one who promises to be with us is the one to whom all authority in heaven and earth has been granted. We are not to go out preaching the gospel expecting only a few among the nations to be converted, while the majority of the earth goes on in paganism. Rather, the testimony of the prophets is that the coming of the Messiah would mean the conversion of the nations. The whole of the earth has been granted to Christ as his inheritance (Psalm 2, Psalm 110). His kingdom, when it comes in the time of the Roman Empire, will grow to fill the whole earth (Daniel 2:31-35). It is like a mustard seed that starts out small but grows into a large tree, or like leaven which works its way through the whole of the dough (Luke 13:18-21). Christ is reigning with all authority and he will continue to reign until all his enemies are under his feet (1 Corinthians 15:25). We look forward to his future reign over the entire earth (Revelation 20:46), when he will have conquered all nations by the sword that comes out of his mouth, his holy word (Revelation 19:15, 21). God has given us the enormous (and undeserved) privilege of being his ambassadors, the ones who preach the gospel which goes forth with power for the overcoming of the nations.
In Christian history, we have seen these promises at work. Christ's disciples started out a small group of unimportant men in Judea. For hundreds of years, they were persecuted not only by the Jews but by the mighty Roman Empire. The Empire commanded them to submit to Caesar as the ultimate Lord, but the church refused, instead demanding that the Empire submit to Christ as the ultimate Lord. Who would we expect to have won this contest? Humanly speaking, the church had no chance. But by God's power and grace, in accordance with his promises, it was the Empire which eventually submitted, declaring that Christ indeed is Lord. Many other examples of God's power through the preaching of the gospel throughout history could be given. The very fact that most of us are Gentiles living in what to ancient Israel would have been considered the remote corners of the earth, and yet here we are discussing how to glorify the true God in his church, is a dramatic testimony of God's faithfulness in making his Messiah a light to the nations.
But the work of the church is not finished. There are nations yet to be converted. And within nations that once were converted, there is much backsliding. Of course, until the end of the world we should never expect to see perfection, since God has promised us that sin will be with us until the end. But in the present day, at least in some parts of the world (such as Europe and America), it almost appears that the attainments of the church are regressing rather than progressing. When we see this happening, we ought to ask, why?
A definite answer to this question that covers all the causes cannot be given. God has his plans, and he will carry them out as he sees fit apart from any timing we may wish to see. God often allows apparent setbacks to the accomplishment of the good goals he has laid out to occur, even when men are faithful. This is true both for individuals (think of Job) and for nations. However, whenever we see such setbacks, whether in our own lives or in the life of the church and the world at large, we ought to examine ourselves to see if there is any "sin in the camp."
I think there is a very significant sin in our camp today. The church of God is in a deplorable state of division. The followers of Christ are divided into a myriad of conflicting denominations, refusing to formally recognize each others' legitimacy and in many ways in competition with each other. Christ has called us to be one in the truth, and yet we have wandered off into doctrinal and practical errors that have created barriers to the unity we are all called to. When union is sometimes achieved between denominations or groups of Christians, it is often accomplished not by repenting of and removing the real causes of division, but by papering over them in a spirit of apathy to the revealed truth of God. We have grown too comfortable with this state of things, and we continue in many ways to enagage in attitudes and practices that do nothing but hinder true unity.
Could this current state of the church have something to do with the setbacks we are seeing in the world today in terms of the conversion of the nations to a confession and practice of the pure Word of God? I think we must answer yes to this question. We know this is the case because Christ himself promised that it would be the case. In John 17:20-23, in the middle of his so-called high priestly prayer for his people, Jesus says something very startling: "Neither pray I for these alone, but for them also which shall believe on me through their word; that they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me. And the glory which thou gavest me I have given them; that they may be one, even as we are one: I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me."
Jesus ties the conversion of the world into the knowledge of the truth of the gospel to the unity of the church. When the church is properly one, then the world will believe that the Son was truly sent by the Father, and that the church is the people of God.
As we look around us today and wonder when things will turn around, as we wonder why more and more people are turning away from the faith of their fathers, and why the nations in which we live are becoming more and more corrupt all the time, and why the church is not more effective than it is at being a light to the nations, let us consider that our attitudes and actions with regard to the unity of the church, according to Christ's explicit words, should be seen as a cause of these problems. The unity of the church is not only an important ideal and duty in itself. It is an essential component in the church's goal to evangelize the nations. And we are told explicitly by Our Lord that we cannot expect the latter without the former. Let us, then, seek with great earnestness the true unity of the church--not in compromise and watering down of pure doctrine and practice, but in reform and repentance and loving dialogue that leads us all to move away, by God's grace, from our wicked ways and to unite in the purity of God's truth.