Per the Nicene Creed:
We believe in one holy, universal, and apostolic Church
Per the Holy Bible:
The human body has many parts, but the many parts make up one whole body. So it is with the body of Christ. Some of us are Jews, some are Gentiles, some are slaves, and some are free. But we have all been baptized into one body by one Spirit, and we all share the same Spirit.
So now you Gentiles are no longer strangers and foreigners. You are citizens along with all of God’s holy people. You are members of God’s family. Together, we are his house, built on the foundation of the apostles and the prophets. And the cornerstone is Christ Jesus himself. We are carefully joined together in him, becoming a holy temple for the Lord. Through him you Gentiles are also being made part of this dwelling where God lives by his Spirit.
Now these are the gifts Christ gave to the church: the apostles, the prophets, the evangelists, and the pastors and teachers. Their responsibility is to equip God’s people to do his work and build up the church, the body of Christ. This will continue until we all come to such unity in our faith and knowledge of God’s Son that we will be mature in the Lord, measuring up to the full and complete standard of Christ.
Then we will no longer be immature like children. We won’t be tossed and blown about by every wind of new teaching. We will not be influenced when people try to trick us with lies so clever they sound like the truth. Instead, we will speak the truth in love, growing in every way more and more like Christ, who is the head of his body, the church. He makes the whole body fit together perfectly. As each part does its own special work, it helps the other parts grow, so that the whole body is healthy and growing and full of love.
With all these things in mind, dear brothers and sisters, stand firm and keep a strong grip on the teaching we passed on to you both in person and by letter.
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Contrary to the signs outside all the church buildings around the world that proclaim different denominational names and conferences and traditions, there is only one Church, and it spans all man-made distinctions and trivial divisions. Christ is the head of this one Church, which is comprised of all persons who have been joined to him through faith. The Church is not limited to any particular time, place, ethnic group, language, religious heritage, denomination, or institution.
As for the word "apostolic"? It comes from the Greek word for people who are sent on a mission (apostello). As Christ was sent into the world, he has sent his followers into the world (John 17). The Church is apostolic not only because we are sent on a mission, but because the teachings of the first apostles - those called and sent by Jesus himself - are authoritative for the Church. The New Testament Scriptures have apostolic authority and are God-breathed.
Truth is...No matter what side discussions and opinions about controversial subjects may seek to divide us, the Church stands united by the Love of the Father, the Lordship of Jesus, and the Leading of the Holy Spirit. The main things are the plain things and the plain things are the main things.