God’s method and means of fulfilling His eternal purpose is by way of “the church, which is His (Christ’s) body”. The Church is definitely stated to be “the fullness of Him that filleth all in all”. That universal fullness of Christ is determined to be revealed and expressed in and through a vessel called the Church. What is this Church?
Firstly, it is said to be an elect company of people. Leaving all theories of election, let us be content, for the moment, to see that God has eternally determined to have such a company, and that election is related to purpose, not primarily if at all to salvation. God knows, He cannot help knowing, the ultimate reactions of people to His presentations, and according to His foreknowledge He has foreordained to His purpose. But God has never said to any unsaved person that he or she is so foreordained. He only calls. The Church is the company of the called who obeyed.
Secondly, the Church is something greater than the churches. The Church is essentially a spiritual thing; not sectarian, denominational, “ecclesiastical,” traditional, etc. It is the spiritual relatedness as of a living organism; a body possessing one life; it is a single entity, an “all one in Christ”. The measure of light does not make for a more or less membership of that Body, although that may affect functioning. The apprehension of “Church Truth” does not constitute Church membership, although it will greatly affect the matter of fullness. Vital relatedness to Christ is the basis of Body actuality.
But when we have said that, we must point out how important the recognition of the Church is. Next to the revelation of Christ personally in His greatness, the revelation of the Church is bound up with our practical progress toward fullness. Paul has a far greater fullness in his writings than any other Apostle, and this is mainly due to the specific revelation of the Church which was given to him. What arises from this revelation is that Christ and the Church are one, as Head and members of one Body.
For more excellent teaching on The Church: https://www.youtube.com/watch?v=mXOuWz2AnUI