The Bible speaks of two kinds of unity. A false unity that is based on man’s agenda to glorify self (Gen. 11:1-9). This is the ecumenical movement of the 21st century that is driven by apostasy, tolerance and the compromise of God’s Gospel. It is the false unity of the antichrist and must be earnestly resisted by God's people. 

There is also a true unity of the Spirit which all Christians are encouraged to keep (Eph. 4:3). Born-again Christians are baptized by the Holy Spirit into one body to serve one Lord, one God and Father of all. (Eph. 45-6; 1 Cor. 12:13). This is the unity of the one true and settled faith taught by the apostles. God's people are exhorted to "earnestly contend for the faith once delivered unto the saints" (Jude 3). There can be no unity between those who are sanctified by the truth and those who are not. When Christians attempt to practice unity with unregenerate professing Christians, there must always be compromise because true faith, based on the Word of God, causes division rather than unity. It is impossible to stand steadfast on the truth of God’s Word and to be ecumenical at the same time. The apostle Paul encouraged Christians to "let your manner of life be worthy of the Gospel of Christ, so are standing firm in one spirit, with one mind striving side by side for the faith of the Gospel” (Phil. 1:27). This is the kind of unity described in John 17. Jesus prayed to His Father that those who have been sanctified by the truth may all be one (John 17: 17, 21) This can only become a spiritual reality when genuine believers submit to the supreme authority of Christ and His Word.