Let me clear this up, for a moment. First, apostolic is neither ‘Catholic’ nor, well, ‘Apostolic.’ It simply means a church that goes back to the time of the Apostles. Granted, that word, like ‘catholic’ takes on a different meaning later in life.
Just to emphasis this: one means unity.
The church throughout all the world, having its origin firmly from the apostles, perseveres in one and the same opinion with regard to God and his Son. Irenaeus, Against Heresies 3.12.17
Between us we have but one church; we are united in heart; we are inseparable in concord. What bishop would not, there fore, rejoice in the honors of his brother bishop as if they were his very own? Where is the community of brothers who would not take delight in the joy of their fellows? Cyprian, Letter 60.1
Blessed are you, O church, for Isaiah also exulted in you in his prophecy: Behold, a virgin shall conceive and bear a child whose name is a mighty symbol. O the meaning revealed in the church! Two names, which have united and become one, Emmanuel, God with you at all times, since he united you with his members. Ephrem the Syrian, Hymns on the Nativity 25.5
Look on the prophets and the apostles, how like they are to each other! The prophets gave the name of God to the flock of God, and the apostles gave the name of Christ to the church of Christ. Ephrem the Syrian, Nisibene Hymns 20.7
This section was filled with lots of long quotes, longer than I cared to type, but each one important. They strong for unity, not around men or ideals, but around Truth, around Christ. Would that we do the same.