Apologeticae sive Theologiae Fundamentalis, Tomus II (Pars Altera): Demonstratio Catholica

The discussion is not about mathematical unity, by which the Church is one, but about moral unity, by which it is undivided. That the Church is one we have already proved. It remains, however, to be shown that by Christ's institution it is undivided, or morally one, both by the unity of creedal confession and by the unity of social communion: by the unity of confession, which recoils from heresy, and by the unity of communion, which forbids schism.

It is to be presumed that the Church excels by the confession of one faith, since it follows the one Christ as teacher and is subject to the one magisterium established by Christ. The following expressly require the unity of the symbolic confession:

1. Christ. Christ commanded the apostles to "teach all nations", and indeed to "teach all things, whatsoever He commanded", and to preach the "gospel" in its entirety "to every creature".¹ To these precepts He simply adds: "He who believes and is baptized will be saved; but he who does not believe will be condemned."² Therefore the teaching Church is bound to preach the same evangelical doctrine everywhere and to all men, and the learning Church, in its entirety and everywhere, is bound to profess the same evangelical doctrine. And this with the added sanction of eternal salvation and eternal punishment. From this there undeniably arises the unity of the symbolic confession, whereby every heresy is kept away from the Church.

2. Paul. Paul, solicitous about the unity of faith, teaches the Ephesians: "One Lord, one faith, one baptism, one God and Father of all"³ He reproaches the Galatians: "I marvel that you are so quickly transferred from him who called you into the grace of Christ, to another gospel, which is not another; but there are some who trouble you and want to pervert the gospel of Christ. But even if we or an angel from heaven preach to you a gospel other than that which we preached to you, let him be anathema."⁴ He warns Titus: "Avoid a heretical man after one and a second admonition, knowing that one who is such is subverted and sins, being condemned by his own judgment."⁵ He entreats Timothy: "O Timothy, guard the deposit, avoiding profane novelties of words and oppositions of knowledge falsely so called, which some promising have erred concerning the faith."⁶

3. Christian antiquity. From the innumerable testimonies that bear upon this matter we draw out these few. St. Irenaeus says: "The true and universal Church holds one and the same faith throughout the whole world."⁷ He describes the preaching of the Church as "everywhere constant and equally persevering".⁸ Theodoret explains: "Just as any city contains within itself many houses divided among themselves and yet is called one city, so the churches are infinite and innumerable, on the islands and on the continent, and at the same time all are brought back into one, united by the consonance of true dogmas."⁹ St. Augustine writes about the Church: "The raiment of this queen [the Church] … is precious and varied: the sacraments of doctrine in all the various languages … But just as all the variety of the garment agrees in unity, so too all languages [agree] unto one faith … Whatever the variety of languages, one gold is preached: not diverse gold, but variety from gold. For all languages preach the same wisdom, the same doctrine and discipline. Variety in the languages, gold in the sentences."¹⁰ Above the testimonies of these and of other individual fathers stand the creeds prescribed to the whole Church by the first ecumenical councils for the preservation of unity. Such a creed the first Nicene council already prescribed to be professed, adding an anathema against those who would believe otherwise.¹¹

By these texts of Christ, of Paul, and of antiquity, the unity of the symbolic confession is not only demanded but also defined, so that it extends to the whole revealed doctrine and to it alone. To the whole revealed doctrine: whence certain Protestants wrongly contend that for the unity of faith in the Church, and likewise for attaining eternal salvation, agreement on the "fundamental" articles suffices, while the "non-fundamental" ones can be denied without detriment to unity and salvation.¹² To the revealed doctrine alone: whence the unity of the Church can be perfect, although various ecclesiastical laws, various liturgical forms, various theological opinions, etc. are found. Provided that all things which Christ revealed are preached and believed everywhere and by all.

The social communion of the Church consists in this, that all the faithful, through one and the same hierarchical government, are gathered together into one and the same organism, with every schism excluded. The following expressly require this unity of social communion:

1. Christ, because He instituted the Church as a society properly and strictly so called, and everywhere describes it by the metaphors of a kingdom, a city, a house, a sheepfold, a flock. All of which presuppose the social unity of the Church. To obtain this unity among His own and to strengthen it forever, Christ poured forth a prayer to the Father: "Holy Father, keep them [the apostles] in thy name, whom thou hast given me, that they may be one, as we also are … And not for them only do I pray, but for them also who through their word shall believe in me: that they all may be one, as thou, Father, in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me. And the glory which thou hast given me, I have given to them: that they may be one, as we also are one: that they may be made perfect in one and the world may know that thou hast sent me and hast loved them, as thou hast also loved me."¹

2. Paul. For he describes the Church, as we already know, very often by the metaphor of the human body, signifying that it is one moral whole, just as the human body is one physical whole. "For as the body is one and has many members, and all the members of the body, whereas they are many, yet are one body: so also is Christ [the mystical = the Church]. For in one Spirit were we all baptized into one body … The members indeed are many, but one body. And the eye cannot say to the hand: I have no need of thy works: or again the head to the feet: You are not necessary to me … that there may be no schism in the body, but the members might be mutually solicitous one for another … But you are the body of Christ, and members of member.² Just as all the members of the body coalesce in an orderly and intimate manner into one body; just as the individual members have their own office and are helped and fostered by the other members; just as there is no schism in the body, but a mutual unity of communion and charity: so also is the mystical body of Christ, i. e. the Church.

3. Christian antiquity. The Fathers exceedingly abhorred schisms and forbade every communion of the faithful with schismatics, e. g. already s. Ignatius: "If anyone follows one who makes a schism, he shall not obtain the inheritance of the divine kingdom."³ The faithful who were about to travel abroad, that they might be admitted in foreign churches, were furnished with letters, as they called them, canonical communicatory or formatae.⁴ By similar letters given and received the bishops testified to union with other bishops and other churches;⁵ but above all they proved social communion with the universal Church by formatae sent to the Roman pontiff and received in turn from him.⁶

In truth, the unity of creedal confession and of the social communion of the whole Church is ultimately effected, preserved, and demonstrated solely by union with the supreme pontiff. The members of the human body constitute one body, inasmuch as through every joint of supply they cohere to the head;⁷ the faithful of the Church visibly constitute one mystical body of Christ, inasmuch as through the bishops they cohere to the supreme pontiff, the visible head of the Church.