Silo-ettes
Protestant ecclesiology is an outgrowth of papal ecclesiology.
First, medieval theologians distinguished three concepts that, in their view, had been conflated in the term "Body of Christ": the natural human body of Jesus Christ, the Eucharistic mystery, and the Church.
The application of the concept of "body" to the Church was developed in accordance with the concept of "corporation" inherited from Roman law and distinguished from the body of Christ in the sense of the Eucharistic mystery. The Church as corpus would, in effect, become a juridical corporation. As explained by Ernst Kantorowicz, medieval theologians and jurists, in order to justify the continuity of the organic unity of an institution through time, distinguished three temporal modalities: aeternitas, aevum and tempus. Within the scope of aevum, the ecclesial corporation acquires the dimension of perpetuity common to angels and celestial intelligences, being neither eternal like God nor strictly temporal like individual men (cf. Vatican I: "the perpetuity of the primacy of blessed Peter in the Roman pontiffs"). It is in this sense of aevum that the epithet mysticum henceforth came to be applied to the Church. The Church as a legal corporation is what is denoted by the syntagma corpus mysticum. As Henri de Lubac demonstrated, the adjective mysticum, originally belonging to the sacramental sphere in the West, was gradually transferred to the legal sphere of the institution.
As a unitary juridical entity distinct from its constituent members, the Church as a corporation acquires the legal status of a persona ficta. Yet, insofar as the papal conception of the Church is monarchical, the persona ficta of the Church cannot but be the Pope himself. The Pope is, in this sense, the head of the ecclesial juridical corporation, endowed with a legal personality independent of its members. This legal personification of the Church implies a surreptitious separation and subsequent hypostatization of its dual divine-human reality, whose new relation of representation recalls the Nestorian notion of the "prosopic union" of the human and the divine in Christ.
Papal ecclesiology further articulated this legal and corporate notion through the dual conception of the Church as Ecclesia militans β the visible Church β and Ecclesia triumphans β the invisible Church. Submission and obedience to the Pope, as the foundation of membership in the visible corporate Church, became the necessary condition for access to the triumphant Church, the invisible and heavenly counterpart of the visible Church on earth.
Eucharistic communion ceases to be the operative means by which the faithful are incorporated into the Body of Christ. The body of Christ present in the Eucharistic mystery ceases to be the sacramental foundation of the Church and is relegated to a secondary role, becoming merely a sign of belonging to the corporate Church, whose foundation is obedience to the Pope.
Reformers such as Luther and Calvin would adopt this notion, though now to designate the Church as a mystical body (spirituale et arcanum Christi corpus) β spiritual and invisible β, as opposed to the Church as a political and visible body (corpus politicum dumtaxat).
This idea of the mystical and invisible Church would also be appropriated by the esoteric movements of the seventeenth century, such as Rosicrucianism, and later by Freemasonry.
The separation of the Church from the eucharistic body of Christ opened the door to the conception of an esoteric and mystical ecclesia distinct from the Body of Christ as such. Contrasted with the representation of the Catholic Church as a merely political and external institution, this notion would come to assume the contours of an ecclesia not confined to Christianity itself, but transcending it, with Christianity conceived as an exoteric religion.
In the context of the Protestant movements, the emphasis on understanding the Church as the invisible Church β the true corpus mysticum of Christ, distinct from and opposed to the corrupt papal institution β resulted in the impossibility of drawing institutional boundaries between Church and State, since the Church, as corpus mysticum interpreted in this new sense, possessed no visible earthly form. Thus, all political and institutional aspects of the Protestant denominations were necessarily left in the hands of the princes who protected the various congregations and, ultimately, in the hands of the state.