The Church is one. Her unity follows of necessity from the unity of God; for the Church is not a multitude of persons in their separate individuality, but a unity of the grace of God, living in a multitude of rational creatures, submitting themselves willingly to grace. Grace, indeed, is also given to those who resist it, and to those who do not make use of it (who hide their talent in the earth), but these are not in the Church. In fact, the unity of the Church is not imaginary or allegorical, but a true and substantial unity, such as is the unity of many members in a living body.
The Church is one, notwithstanding her division as it appears to a man who is still alive on earth. It is only in relation to man that it is possible to recognize a division of the Church into visible and invisible; her unity is, in reality, true and absolute. Those who are alive on earth, those who have finished their earthly course, those who, like the angels, were not created for a life on earth, those in future generations who have not yet begun their earthly course, are all united together in one Church, in one and the same grace of God; for the creation of God which has not yet been manifested is manifest to Him; and God hears the prayers and knows the faith of those whom He has not yet called out of non-existence into existence. Indeed the Church, the Body of Christ, is manifesting forth and fulfilling herself in time, without changing her essential unity or inward life of grace. And therefore, when we speak of the Church visible and invisible, we so speak only in relation to man.
The Church visible, or upon earth, lives in complete communion and unity with the whole body of the Church, of which Christ is the Head. She has abiding within her Christ and the grace of the Holy Spirit in all their living fullness, but not in the fullness of their manifestation, for she acts and knows not fully, but only so far as it pleases God.
Inasmuch as the earthly and visible Church is not the fullness and completeness of the whole Church which the Lord has appointed to appear at the final judgment of all creation, she acts and knows only within her own limits; and (according to the words of Paul the Apostle, to the Corinthians, 1 Cor. 5. 12) does not judge the rest of mankind, and only looks upon those as excluded, that is to say, not belonging to her, who exclude themselves. The rest of mankind, whether alien from the Church, or united to her by ties which God has not willed to reveal to her, she leaves to the judgment of the great day. The Church on earth judges for herself only, according to the grace of the Spirit, and the freedom granted her through Christ, inviting also the rest of mankind to the unity and adoption of God in Christ; but upon those who do not hear her appeal she pronounces no sentence, knowing the command of her Saviour and Head, not to judge another man’s servant (Rom. 14. 4).
[Read it all at the link above.]