Having finished our study of baptism, we are now prepared to look more closely at the Lord’s Supper. Before we do that, however, we will take a break from our look at the biblical doctrines summarized in the Heidelberg Catechism for a brief study of the church, the people of God to whom the sacramental means of grace have been given. Dr. R.C. Sproul’s teaching series The Bride of Christ will help us understand different aspects of ecclesiology (the doctrine of the church). Scripture describes many attributes of the church, not the least of which is the church’s unity or oneness. Today’s passage is an important text on this subject. Jesus’ High Priestly Prayer in John 17 demonstrates how important it is to God that His church be united in its purpose and mission. In fact, this unity reflects the oneness of the Father and the Son. Moreover, Jesus says that the oneness of the church is one proof to the world that He came from our Father (vv. 20–21). Of course, the church is made up of sinners, and we have not always done a good job demonstrating the unity of the people of God in Christ. We see the visible church fragmented into many different denominations. This is surely regrettable, as sin is the root cause of all church divisions. In some church splits, a group breaks off because the church is guilty of denying the gospel. In other splits, the group that breaks off is the guilty party because it is in doctrinal error or has elevated nonessentials to matters of gospel truth. Sometimes, both parties are guilty. Consequently, many people try to overcome these divisions. Unfortunately, many do so at the expense of true unity, continuing to receive as brothers and sisters those who deny the essentials of the gospel. If unity is to mean anything, it must be unity grounded in the truth of God’s Word. This is the kind of unity for which Jesus prayed (vv. 17–19). Unity for the sake of visible oneness alone, however, is not pleasing to God. As the Apostle Paul demonstrates, there can be no compromise when the gospel of God is at stake (Gal. 1:6–9; 2:15–16). Unity in the gospel is the prerequisite for the unity of the church. Christians who affirm the essentials of the gospel are even now united invisibly, enjoying a special communion with one another across denominational lines.