Ecclesiology for people in the churches is an underdeveloped, and even undeveloped teaching for most. Unless a Christian person is self-motivated to pursue study of this important doctrine they will most likely live their Christian existence within the darkness of absence (of teaching). I think this, in fact, has a lot to do with many so-called Protestant Christians swimming the shallow end of the Tiber River; i.e., to become members of the Roman Catholic church. In nuce, Roman Catholic ecclesiology entails the notion that the Roman church itself prolongates the incarnation of Jesus Christ. That is to say, that the Roman ecclesia, for proponents of Roman Catholic theology, believe that its church is the visible embodiment of Jesus Christ Himself; thus, their reference to the mystici corporis Christi (‘mystical body of Christ’). Here is a snippet of a longer encyclical that Pope Pius XII wrote for the Catholic church with reference to understanding just what the Roman Catholic understanding of the Church is:

But if our Savior, by His death, became, in the full and complete sense of the word, the Head of the Church, it was likewise through His blood that the Church was enriched with the fullest communication of the Holy Spirit, through which, from the time when the Son of Man was lifted up and glorified on the Cross by His sufferings, she is divinely illumined. For then, as Augustine notes, [39] with the rending of the veil of the temple it happened that the dew of the Paraclete’s gifts, which heretofore had descended only on the fleece, that is on the people of Israel, fell copiously and abundantly (while the fleece remained dry and deserted) on the whole earth, that is on the Catholic Church, which is confined by no boundaries of race or territory. Just as at the first moment of the Incarnation the Son of the Eternal Father adorned with the fullness of the Holy Spirit the human nature which was substantially united to Him, that it might be a fitting instrument of the Divinity in the sanguinary work of the Redemption, so at the hour of His precious death He willed that His Church should be enriched with the abundant gifts of the Paraclete in order that in dispensing the divine fruits of the Redemption she might be, for the Incarnate Word, a powerful instrument that would never fail. For both the juridical mission of the Church, and the power to teach, govern and administer the Sacraments, derive their supernatural efficacy and force for the building up of the Body of Christ from the fact that Jesus Christ, hanging on the Cross, opened up to His Church the fountain of those divine gifts, which prevent her from ever teaching false doctrine and enable her to rule them for the salvation of their souls through divinely enlightened pastors and to bestow on them an abundance of heavenly graces.[1]

The Roman Catholic church maintains, as indicated by Pope Pius XII, that the Holy Spirit, as the enlivener and Creator of the Church has so mystically tied Himself into the visible manifestation of the Roman See, along with all of her sacraments, hierarchy of pastors, so on and so forth, that the only ‘place’ union with God in Christ can obtain is if someone is brought into union with the mystical body of Jesus Christ; or, in the Roman view, with the Roman Catholic church herself. This union is supervened by the bishops and priests of the Catholic church, not least of which, is the Pope himself. Once inducted and confirmed into the Catholic church, through baptism and partaking in the Mass of the sacraments, it is at this time that the Catholic convert becomes a ‘feeder’ on and mystical participant within the visible body of Christ on earth; or the Roman Catholic church. In this sense, and per Pius XII’s aforementioned words, there is a real sense wherein the Roman ecclesiology, with its insistent assertion on their status as the visible body of Christ on earth, that the Church itself becomes a prolongation of the incarnation. That is, for the Roman, the Church has become and is so entwined with the notion that Roma is now the apple of God’s eye, that she alone is God’s visible body on earth; that in order for communion with God to obtain for humanity, would-be Christians must come into, again, union with the mystical body of Christ; which is none other, according to Roman doctrine, but the Latin Catholic church.

Protestants, on the other hand, rooted in a radical theology of the Word of God, maintain that the body of Christ is fully present within the vicarious humanity of Jesus Christ; indeed, even as Christ has resurrected with that body, ascended with that body, intercedes in priestly session at the right hand of the Father with that body, and will come again with that body; His glorified body. For the Protestant, thusly, there is no prolongation of the incarnation of Christ as a mystical body of Christ, but rather its concrete existence in the flesh and blood of Imannuel’s veins as He has freely elected to be for us, with us, and not God without us in Jesus Christ.

Hence, Protestants are not burdened with the notion that we must present some type of mystical body of Christ to each other and the world writ large, as if that body is constituted by a physical address in Vatican City, Italy. On the contrary, Protestants understand that the esse of the Church is constituted by the literal body of Christ Himself for us. Resultantly, the Protestant doesn’t seek to point a would-be or already Christians to a particular iteration or expression of the Church in the world as the Roman does. The Protestant understands that their respective Christian existence is constituted, indeed by the Holy Spirit, by way of union with Christ immediately, directly. The Protestant bears witness to the finished work of God in Christ as the reality (res) of the Church in the triune God. Karl Barth writes on this status of the Protestant Christian similarly,

. . . Their existence in the world depends upon the fact that this alone is their particular gift and task. They have not to assist or add to the being and work of their living Saviour who is the Lord of the world, let alone to replace it by their own work. The community is not a prolongation of His incarnation, His death, and resurrection, the acts of God and their revelation. It has not to do these things. It has to witness to them. It is its consolation that it can do this. Its marching-orders are to do it.[2]

Barth rightly notes that the work of the Church is absolutely finished in the work of Jesus Christ. It is His work of salvation, of building His Church, that He has already accomplished; the Church’s task, by the Spirit, is to bear witness to this, her reality, in her Head and reality, Jesus Christ. The Roman church, alternatively, believes that it constitutes itself by re-presenting the Mass, the death of Jesus Christ, through the primary sacraments of baptism and the eucharist. There remains an unfinished work within the Catholic ecclesiology which makes the prolongation of the incarnation of Jesus Christ the most organic outcome. That is, because their remains a proving ground, so to speak, of the Christian’s worth to inherit eternal life through the treasuries of Christ’s merits, over and beyond the work of Christ’s atonement. And so, for the Catholic Christian, the Mass and its sacraments remain the portal whereby salvation might be constantly offered, affirmed, reaffirmed, over and again, as the Christian seeks to establish a level of sanctification whereby they are found worthy enough to in fact become real and ultimate participants within the mystical body of Christ. If the Church, as it is for the Roman, is a prolongation of the incarnation, then the incarnation, logically, requires further re-establishment and curation by the faithful; if in fact, the body of Christ can be shown to be the true body of Christ in the world today.

This requires further fleshing out. But hopefully there has been enough provided for the reader to start to digest.

[1] Pope Pius XII, MYSTICI CORPORIS CHRISTI: ENCYCLICAL OF POPE PIUS XII ON THE MISTICAL BODY OF CHRIST TO OUR VENERABLE BRETHREN, PATRIARCHS, PRIMATES, ARCHBISHOPS, BISHIOPS, AND OTHER LOCAL ORDINARIES ENJOYING PEACE AND COMMUNION WITH THE APOSTOLIC SEE, published by, The Holy See, accessed 05-05-2026.

[2] Karl Barth, Church Dogmatics IV/1 §59 [318] The Doctrine of Reconciliation: Study Edition (London:T&T Clark, 2010), 312.