I’d like to advance two theses. First, there is a great theological difference between churches and the Church. Secondly, the Baha’i Faith is the Church; or framed differently: The Baha’i Faith is the Return of the Church.
So what’s the difference between churches and the Church?
The Bible speaks of many churches. There is the church at Jerusalem, the church at Antioch, Rome, etc. These are the different communities, the diverse sites that believers can be found. But beyond that there is a greater sense in which the word church is used. This sense employs a relationship not only between human beings and their physical locations, but also, with Jesus, the one who calls the Church together. The unity of Christ is the unity of the Church. “Church” refers to a spiritual, not a social bond. It concerns the relations between other people only through the mediation of their relation to the Messiah. I address this in greater depth in the entry, “The Church and her Truth,” posted below. That entry examines Paul’s critique of sectarianism among the Corinthian faithful. Though the believers may divide themselves this way and that they are still participants in only one Church. Related to this is the way Paul conceives of the Church as a body. In the same epistle, he discusses the unity of the community in the diversity of its members. In these statements what unites the diverse aspects is always their connection with God, rather than the human bonds between its individual members.
"There are many different gifts, but it is always the same Spirit; there are many different ways of serving, but it is always the same Lord. There are many different forms of activity, but in everybody it is the same God who is at work in them all..."
"For as with the human body which is a unity although it has many parts- all the parts of the body, though many, still making up one single body- so it is with Christ. We were baptized into one body in a single Spirit, Jews as well as Greeks, slaves as well as free men, and we were all given the same Spirit to drink."
The Church may have many social and doctrinal cleavages within it. But still there is only one Church by way of its members’ other-worldly connection with the Messiah. Paul writes in his letter to the Collosians,
He exists before all things and in him all things hold together, and he is the Head of the Body, that is, the Church.
The Church is a Communion extending between heaven and earth, and on earth between souls joined in the Spirit with the Messiah. This means that no earthly power can dissolve the Church. Its fundamental unity is in Christ. The social breakup of communities and institutions is only an outward scar on its Body. The Messiah is the beginning of the Church and he is its end. Only through him, can its fundamental reality be altered. With that in mind it is possible to see how the Baha’i Faith is the Return of the Church. In the act of returning, Baha’u’llah restores his relationship to the faithful. Those who are united with him are the continuation of this sacred body. Communities of Christians may reject or remain unaware of Baha’u’llah, (for now, it’s usually the latter) but inasmuch as they are in the Church, they participate in the sanctity of its life by way of Baha’u’llah. And just as the one Church may have many social divisions without dissolving itself as Church, so too the Church can extend across the dividing lines of religions and still be Church.
 1 Cor 12.4-6
 1 Cor 12.12-14
 Col 1.17-18