Unity between Denominations? Part II: What kind of unity are we called to?

Last time, I looked at the problem posed by denominationalism: namely, how the unity among Christians demanded by Christ is possible while also preserving the one true faith.

Today we'll consider a collection of the descriptions of the kind of unity we are meant to have, straight from Sacred Scripture.

• Rom. 12:4-5 "For as in one body we have many members, and all the members do not have the same function, so we, though many, are one body in Christ, and individually members one of another."
• 1 Cor. 12 "For just as the body is one and has many members, and all the members of the body, though many, are one body, so it is with Christ. For by one Spirit we were all baptized into one body -- Jews or Greeks, slaves or free -- and all were made to drink of one Spirit. For the body does not consist of one member but of many... If one member suffers, all suffer together; if one member is honored, all rejoice together. Now you are the body of Christ and individually members of it."
• Eph. 4:1-6 "I therefore, a prisoner for the Lord, beg you to lead a life worthy of the calling to which you have been called, with all lowliness and meekness, with patience, forbearing one another in love, eager to maintain the unity of the Spirit in the bond of peace. There is one body and one Spirit, just as you were called to the one hope that belongs to your call, one Lord, one faith, one baptism, one God and Father of us all, who is above all and through all and in all."
• Phil. 1:27 "Only let your manner of life be worthy of the gospel of Christ, so that whether I come and see you or am absent, I may hear of you that you stand firm in one spirit, with one mind striving side by side for the faith of the gospel."

The Last Supper, where Christ prayed that we would be one. (Jn. 17)

• Phil. 2:2 "complete my joy by being of the same mind, having the same love, being in full accord and of one mind."
• Col. 3:14-15 "And above all these put on love, which binds everything together in perfect harmony. And let the peace of Christ rule in your hearts, to which indeed you were called in the one body. And be thankful." 
• 1 Cor. 10:16-17 "The cup of blessing which we bless, is it not a participation in the blood of Christ? The bread which we break, is it not a participation in the body of Christ? Because there is one bread, we who are many are one body, for we all partake of the one bread."
• 1 Cor. 1:10 "I appeal to you, brethren, by the name of our Lord Jesus Christ, that all of you agree and that there be no dissensions among you, but that you be united in the same mind and the same judgment."
• Jn. 10:16 "So there shall be one flock, one shepherd."
• Jn. 17:20-26 "I do not pray for these only, but also for those who believe in me through their word, that they may all be one; even as thou, Father, art in me, and I in thee, that they also may be in us, so that the world may believe that thou hast sent me. The glory which thou hast given me I have given to them, that they may be one even as we are one, I in them and thou in me, that they may become perfectly one, so that the world may know that thou hast sent me and hast loved them even as thou hast loved me."
• 1 Pet. 3:8 "Finally, all of you, have unity of spirit, sympathy, love of the brethren, a tender heart and a humble mind."

Again and again, we are called to be one, which seems to entail both visible (one body, one flock) and invisible (in the one Spirit) unity, through confession of one faith (without dissension!), unified celebration of sacraments (one Baptism, one bread), together bound up in love.

The picture painted here is, I think, very different to what we see today.

Part III: The Witness of the Early Church in the New Testament