Now I beseech you, brethren, by the name of our Lord Jesus Christ, that ye all speak the same thing, and that there be no divisions among you; but that ye be perfectly joined together in the same mind and in the same judgment. For it hath been declared unto me of you, my brethren, by them which are of the house of Chloe, that there are contentions among you. Now this I say, that every one of you saith, I am of Paul; and I of Apollos; and I of Cephas; and I of Christ. Is Christ divided? was Paul crucified for you? or were ye baptized in the name of Paul? (1 Corinthians 1:10-13)
The Scriptures are not thrilled with the idea of people joining sects. Rather, the church is to be one and live in unity. While there is diversity amidst the Body, we are not to join into clubs and cliques within the catholic church and separate ourselves from each other.
And yet that is precisely what must happen if we think of the church the way the semi-congregationalists in the modern Reformed churches do. They see the de jure visible church as nothing other than a large conglomeration of independent denominations, with no formal, organic unity and mutual accountability. In this way of thinking, it is impossible to join the catholic church without at the same time joining some particular sect within it, for it does not exist outside of its independent sects. So, for example, if I go to an OPC church where semi-congregationalist thinking prevails and I ask to join the catholic church, they will proceed to lead me to join the OPC. If I ask them if the OPC is the same as the catholic church, they will say, "No, we are only one part of it. There are lots of other denominations--such as the PCA, the RPCNA, the FCC, the RCJ, etc., etc.--which are also parts of it." If I tell them that I don't wish to join a particular sect within the catholic church but simply to join the catholic church, they will look at me blankly, for there is nothing in their view which corresponds with what I am asking. And yet there should be. Why should I have to join "the OPC club" when what I want is to join the one, holy, catholic, and apostolic church? Where is the biblical requirement that I must join a particular club within the church when I join the church? Sure, I ought to join some particular congregation if I can, but where is the biblical warrant for having inter-congregational clubs that are independent from each other and have independent church courts and one of which I must join with to be a member of the catholic church? There is no such biblical concept. Rather, the Bible condemns the forming of separated groups within the catholic church and calls the whole Body to exist in unity.
This situation points us to the need to rethink our modern "Reformed" semi-congregationalist attitudes. For more, see here and here.