UNITY OF THE CHURCH. - The Church is one, that is, undivided in herself and distinct from every other society. Therefore unity is an essential property of the Church and one of her distinguishing marks. The unity of the Church can be considered from within, that is, as it appears to her own consciousness of herself (a rather dogmatic point of view); and from without, as it manifests itself to those who are outside her (a rather apologetic point of view).
I. THE UNITY [U.] AS AN ESSENTIAL PROPERTY. - 1. Notion of the unity of the Church. - The unity of the Church is determined by its nature as a supernatural society founded by the Son of God. Just as the human race forms a unity of all the descendants of the first Adam and of Eve, the "mother of all the living" (Gen. 3:20), so the Church, the society or community of the regenerate, forms a unity of all the descendants of the second Adam, Christ, the children of the second Eve, Mary, who is both the representative and the type of the Church (John 19:25-27; Rev. 12). The Church is therefore one in Christ, as also in its priesthood and sacrifice, which is that of Christ. It is one in its Sacraments, especially in Baptism, through which man is incorporated into the unity of the Church and separated from the rest of humanity. Then it is one in the Sacrament of Order, through which there is unity with the past, the apostolic succession, and which is the indispensable condition for the Sacrament of Sacraments, the Eucharist, which unites with Christ and with all those who are in Christ; whence it is called by excellence "the Sacrament of unity."
The Church, one in all its ontological reality, is also one in its truth, in its magisterium and in its faith. Furthermore, the Church is one in its organic hierarchical government. The unity of the magisterium and of government is essentially concentrated in the one visible head of the Church, the Roman Pontiff, Vicar of the one invisible head Christ and sole successor of Peter, to whom the principate of the apostolic succession goes back. The characteristic unity of the Catholic hierarchy, of bishops and priests, and of the Catholic laity, consists in union with the successor of St. Peter.
Other kindred notions enter into the scope of unity. The uniqueness of the Church is its unity insofar as it excludes any other like it. Then the unity of the Church can be considered in the succession of time, insofar as the Church of today is identical with that of yesterday and tomorrow (v. CHURCH); it can be considered in the grouping of many classes into a whole, in its diffusion through space according to geographical extension among different peoples and nations (v. CHURCH); and it can be considered in its spiritual depth, that is, as union with God through the Grace of Christ (v. HOLINESS OF THE CHURCH). In short, the unity of the Church as such concerns all the bonds by which it is joined as a body to its head Jesus Christ; a truth that St. Paul recalls in Col. 2:19, exhorting us to hold fast "to the head, from whom the whole body, being supplied and knit together through the joints and ligaments, grows with a growth that is from God." The proximate efficient cause of the unity of the Church is the will of Christ, who intended to found one Church only; the ultimate cause is the will and good pleasure of the triune God, Father, Son and Holy Spirit, source and ultimate foundation, in its one divine essence and in its free will, of every existing organic unity; the final cause is indicated by St. Paul when he affirms that all things will be subjected to the Son, as the Son will be subject to the Father, "so that God may be all in all" (1 Cor. 15:28).
2. The sources of Revelation on the unity of the Church
a) Sacred Scripture. - In the Old Testament the Church is prefigured as one in the ark of Noah, the only one saved from the universal flood; in the one chosen people, saved from the Egyptian captivity and led, through the desert, into the promised land; the Church is spoken of when Isaiah announces that "in the last days the mountain of the house of the Lord shall be established on the top of the mountains" (Isa. 2:2). In the Song of Songs the bride is spoken of as a figure of the Church: "One is my dove, my perfect one, she is the only one of her mother, the chosen of her that bore her" (Cant. 6:8). In the New Testament, Jesus speaks twice of the Church, and uses the article (Matt. 16:18 and 18:17). He says expressly that he intended to build "his Church" upon Peter the rock, therefore a single one, distinct from any other that might claim to be a foundation of the "Son of the living God" (Matt. 16:16). St. John reports the discourse of Jesus in which he calls himself "the good shepherd," who foretells that there "will be one fold and one shepherd" (John 10:11; 14; 16), a fold that the risen Jesus entrusts, with all "his lambs" and all "his sheep," to the care of Peter (John 21:15 ff.).St. Paul speaks either of the Church in the singular, meaning the one and universal Church, or of the Churches in the plural, in the sense of particular or local Churches, forming part of the same Church (for example: Rom. 16:16: "all the Churches of Christ salute you"); therefore when he speaks in the singular, the Apostle indicates the Church as one: "Christ is the head of the Church" (Eph. 5:23), which is, according to the same apostle, "his body," "and he is the savior of his body" (ibid. v. 23); he immediately adds: "Husbands, love your wives, as Christ also loved the Church, and delivered himself up for it..." (ibid. v. 25); "for no man ever hated his own flesh: but nourisheth and cherisheth it, as also Christ doth the Church: because we are members of his body, of his flesh, and of his bones" (ibid. vv. 29-30). St. Paul compares the Church to a "bride of Christ"; by this he demonstrates its unity and uniqueness. The bride, being in herself one physical person, is joined to the bridegroom, another physical person, by bonds that are first of all moral; but, furthermore, "the two shall be one flesh" (Matt. 19:5; Gen. 2:24; Eph. 5:31). The body, on the other hand, distinguished by its head, forms, together with it, a unity that is more than moral, that is, organic and physical. From the intertwining of these two images it follows that the unity of the Church is more than purely moral (cf. encyclical Mystici Corporis: AAS, 35 [1943], p. 222).
According to the same St. Paul, the conscious moral union of Christians must correspond to the ontological union of the Church; whence he exhorts the Ephesians to be "careful to keep the unity of the Spirit in the bond of peace. One body and one Spirit, as you are called in one hope of your calling. One Lord, one faith, one baptism. One God and Father of all, who is above all, and through all, and in us all" (Eph. 4:3-6; cf. 1:22-23). In the cited text other exegetes understand "spirit" as said of the Holy Spirit. The unity of the Church therefore comprises the body and the spirit of the faithful, consists in faith and in Baptism and, as still more clearly results from 1 Cor. 12:12-13, in the bond with the Holy Spirit, with Christ and with God the Father: "For as the body is one, and hath many members, and all the members of the body, whereas they are many, yet are one body, so also is Christ. For in one Spirit were we all baptized into one body, whether Jews or Gentiles, whether bond or free: and in one Spirit we have all been made to drink." And as in Baptism, so in the Eucharist the unity of the Church is manifested: "For we, being many, are one bread, one body, all that partake of one bread" (1 Cor. 10:17).
b) Definitions and documents of the Church. - As in the Apostles' Creed, so in all the creeds the profession of faith is made "in the Church" - not in the Churches - "in one Church," "in the one Church." In the Constantinopolitan Creed: "in one, holy, catholic and apostolic Church" (Denz-U, 86). In the profession prescribed for the Waldensians (1208, under Innocent III): "We confess a Church not of heretics, but the holy Roman, catholic and apostolic [Church]” (Denz-U., 423). Famous is the bull “Unam sanctam” of 1302 by Boniface VIII, in which Cant. 6, 8 and Ps. 21, 21 are applied to the Church: “Erue... de manu canis unicam meam,” Io. 19, 23: the “tunica inconsutila”: “hence of the one and only Church there is one body, one head, not two heads as if it were a monster, namely Christ and Christ's vicar Peter, and the successor of Peter” (Denz-U., 468). Three documents must also be recalled: the letter of the Holy Office on the u. d. C. (uniqueness) of 1864 (Denz-U., 1686), the encyclical of Leo XIII Satis cognitum (v.) of 1896 on the u. d. C., an invitation that all return to the u. (Denz-U., 1954 suppl.), and the encyclical of Pius XII Mystici Corporis Christi, quod est Ecclesia of 1943 (AAS, 35 [1943], p. 193 ff.).
c) Christian antiquity. — Very clear on the u. d. C. is the testimony of Christian antiquity and of the Holy Fathers. Already in the Didache one sees, in connection with the Eucharist, in the one bread, gathered from many grains, a symbol of the unification of men in the Church (9, 4; 10, 5). St. Ignatius not only insists on the u. d. C. of the particular [Church] united under a single bishop with his clergy in the eucharistic bread (e.g., Philad., 4; Eph. 20, 2), but also speaks of the “one body of the Church” of Christ in general (e.g., Smirn., 1, 2). In the Shepherd of Hermas “the tower” is the Church (Vis., 3, 5, 1; Sim., 9, 17, 4). For St. Irenaeus the Church “dwells in one house,” has one soul and the same heart, “announces the faith and hands it down” possessing “one mouth” alone (Adv. haeres., 1, 10, 2). For Clement of Alexandria, as one is the Father, the Word, the Holy Spirit, so “she alone becomes a virgin mother: I love to call her Church” (Paedag., 1, 6, 42, 1). And he is of the opinion that “the true Church is one ... the one which the heresies strive to cut up into many” (Strom., VII, 17). According to Tertullian all the Churches descend from the first Church of the Apostles; they are “first and apostolic, if all together they prove the unity” in peace and brotherhood (De praescr. haer., 20, 4).
Most clear is the testimony of St. Cyprian, both in his letters and in the De catholicae Ecclesiae unitate. He writes: “God is one and Christ is one and the Church is one and one is the chair founded upon Peter by the voice of the Lord. One cannot constitute nor can a new priesthood be born outside the one altar and the one priesthood. Whoever gathers elsewhere scatters” (Ep., 43, 5). Or again: “The Church is one, which cannot be one (that is, the same) within and outside. If therefore it is with Novatian, it was not with Cornelius (Pope)” (Ep., 69, 3). In the De catholicum. Eccl. unitate, ch. 5: “The episcopate is one, of which from the individual (bishops) a part is held in solidum. The one Church...; the Church pervaded by the light of the Lord extends its rays throughout the whole world: yet the light is one which is diffused everywhere, and the unity of the body is not separated.” In the text St. Cyprian cites Cant. 6, 8 and Eph. 4, 4 and compares the Church to a fruitful mother, the Church as bride of Christ, and sees her prefigured in Noah's ark (ibid. 6; cf. however PRIMATO DI S. PIETRO E DEL ROMANO PONTEFICE).
Among the great Eastern Fathers and doctors of the 4th and 5th centuries numerous testimonies can be gathered on the u. d. C. of faith and communion of the universal Church. The Roman Primacy as a principle of u. is found there more expressed in facts (doctrinal and disciplinary appeals to the supreme authority) than in doctrine. On the u. of the Body of Christ St. Athanasius, St. Basil, St. Cyril of Jerusalem (explaining the Creed), St. Gregory of Nazianzus, St. Epiphanius are very explicit; St. John Chrysostom especially emphasizes the unity of communion and of charity; St. Cyril of Alexandria too is very explicit on this point. The Western doctors of the same time likewise point out the u. of the Body of Christ: St. Hilary, St. Ambrose, St. Jerome. One of the clearest on this is St. Optatus of Milevis, according to whom Peter, head of all the Apostles, called for that reason Cephas, was bishop of Rome “in whose chair unity is preserved by all, in opposition to the schisms” (Contra Parmenianum Donatistam, II, 2).
The richest, however, is the doctrine of St. Augustine, who illustrates the u. d. C. with various images drawn from Holy Scripture, and insists, in the struggle against the Donatists and Pelagians, on the doctrinal and disciplinary primacy of Rome as center of unity; this doctrine was then clearly expressed by St. Leo the Great, who explained his succession by affirming that Peter was chosen “so that, although in the people of God there are many priests and many pastors, Peter may properly rule them all” (Serm., IV, 2).
d) Theologians. — In the Middle Ages the theology of the u. d. C. was slowly perfected. In St. Thomas are found the great lines of the doctrine on the u. of the body of Christ (Sum. Theol., 3, q. 8). Noteworthy is the De regimine christiano (1301-1302) of James of Viterbo (v.), which treats in a special chapter (1, 3) of the u., seeing in the union of the multitude of the faithful rather a “union” than a “unity.” The first complete exposition on a theological-canonical foundation was written by John Torquemada (v.) in his Summa de Ecclesia, in which he vindicates the u. against the Western and Eastern schismatics.
In modern times, the great speculative theologians Cajetan, De Lugo, Suárez (Disp. IX de fide) set out the principles of the u. d. C. The apologists oppose to the false notes, asserted by the Protestants, the true notes, first of all the u. as the Catholic doctrine understands it. With polemical intent Suárez develops the argument in his Defensio fidei adversus Anglos, St. Robert Bellarmine, Cardinal Du Perron (against the theory of King James of England, that the Church was, in its u., similar to a confederation of religious societies agreeing on a minimum of beliefs), the Jansenist P. Nicole in his treatise De l'unité de l'Eglise ou Réputation du nouveau système de M. Jurieu (Paris 1687). In more recent times the notion of the u. d. C. was re-examined especially under the influence of the revival of patristic studies. One must recall the famous book of J. A. Möhler (v.), Die Einheit in der Kirche oder das Prinzip des Katholizismus, dargestellt im Geist der Kirchenväter der drei ersten Jahrhunderte (1825), by which, in all likelihood, the modern ecclesiologist of the dissident Russians A. S. Chomjakov was inspired in his brief treatise The Church is One (ca. 1845). Before and after the Vatican Council, down to our own day, many treatises De Ecclesia have appeared, which deal extensively with the u. But the impulse to more thorough investigations of the u. d. C. has come from the so-called “ecumenical movement” (v. ECUMENISMO) on the part of Christians now divided into innumerable denominations.
II. THE UNITY OF THE CHURCH AS A DISTINCTIVE NOTE
1. Disunion
Against unity stand schism (v.), cf. 1 Cor. 1:10 (agg.), heresy (v.), and laicization, that is, the gradual separation from the entire work of the Church.2. False concepts of unity
These arose in the course of the centuries, either from the desire to justify one's own schismatic or heretical position, or also from the attempt of Catholics to combat the separations or to clarify the traditional concept of unity. St. Cyprian, for example, in opposing the schism of Novatian clarified many essential traits of ecclesiastical unity, yet he did not always express with sufficient clarity and precision that the unity of government in the Church finds its full realization in the perpetuity of the Primacy of Peter. Thus in modern times Möhler, in explaining to Protestants the true unity of the Church, emphasized too exclusively the internal principle of unity, that is, the Holy Spirit, who brings about the mystical unity, neglecting the external and visible side; he thus arrived at a conception similar to that of St. Cyprian, which, however, he corrected and completed in his later work, the Symbolik (1832).The medieval conciliarism (v.), which placed the unity and authority of ecumenical councils above the Pope, is due in large part to the Western Schism (v.). Analogous is the conciliarism of the dissident Easterners, according to which the individual autocephalous national Churches, independent of one another in government, form a confederation of communities coordinated and connected only by certain bonds of charity that are for the most part rather weak and, from time to time, by an exchange of ideas. A very imperfect form of unity, which not infrequently becomes disunion and even schism (as, for example, the present hierarchy of the patriarchal Church of Moscow is in a state of schism with respect to the hierarchy of the metropolitan Anastasius, formerly resident at Karlovtsi in Yugoslavia, now in New York; the Church of Moscow is likewise in open struggle with the "Ecumenical Patriarch" of Constantinople).
The Easterners, therefore, began to conceive of the unity of the Church, especially from the time of the Slavophile Khomyakov (v.), in a vague and Protestantizing sense, as "sobornost'" (that is, etymologically "conciliarity," historically however identical with "catholicity"), meaning "unity in freedom and in love," allowing the visible unity of the Church to fall into the background; a conception already very close to the Protestant one, which sees the unity of the Church predominantly in the invisible elements of the Body of Christ.
While the dissident Easterners still exclude Catholics and Protestants from the unity of the true Church, that is, their own, because Catholics, according to Khomyakov, have exaggerated the principle of unity and Protestants that of freedom, ecumenism instead has as its basis the so-called "branch theory," according to which the Christian confessions are branches of the same tree. A theory condemned by Pius IX in 1864, insofar as it teaches that the universal unity of the Church should result from the three Christian communities together: the Roman Catholic, the Greek-Selamatic [sic], and the Anglican. Vladimir Solovyov too sometimes expressed himself as if the universal unity of the Church resulted only from the future union between Catholics, dissident Byzantine-Slavs, and Protestants; whence his axiom, "ceterum censeo instaurandam esse Ecclesiae unitatem," is true only in the sense that unity must be restored by the return of the separated to unity.
3. Apologetic value of unity. — Unity is not only an essential property of the Church, but for all those who are outside it, it is a mark of recognition, a way by which to find the true and only Church. It is: a) the most comprehensive mark; the other three (or more) marks can be considered as particular cases of unity (v. above); b) the true and full unity results only from the combination of all the bonds essentially existing in the Church (cf. Col. 2:19), that is, of the bonds of faith, of sacrifice and of the Sacraments, of a single and united government.
III. REALIZATION OF THE UNITY OF THE CHURCH
Besides the efforts and acts of union on the part of the Catholic Church, especially of the Papacy, defined by the Russian Chadayev (1794-1856) as "the visible sign of unity and, since separation has existed, also a sign of reunion," there are also attempts at union on the part of the dissidents, with their successors down to present-day ecumenism, full of genuine impulses, yet essentially fruitless, inasmuch as it seeks to do without the foundation of unity, that is, the rock placed by Christ himself as the foundation of his Church.No one can deny that there is more unity in the Catholic Church than in the dissident Eastern communities, and more among these than among the Protestants of the various denominations. Being unable to deny the fact of the greater unity in the Catholic Church, the dissidents sometimes seek to invalidate its spontaneous and natural apologetic value by asserting that Catholic unity is rather the effect of external coercion than the fruit of intimate conviction.
To reduce the separated to unity, two kinds of centripetal forces are needed: a) the objective ones, instituted by Christ himself, that is, internal Grace and the visible rock of Peter; b) the subjective ones, that is, the freedom of cooperation and the exercise of the Christian unitive virtues, especially of humility and fraternal charity, on both sides, and this in opposition to the centrifugal forces of pride and particularism, granting to all in the common house of God freedom wherever the obligatory unity of dogma is not in question, that is, freedom in rites and in ancient and venerable local customs and traditions. The centripetal and unitive force "par excellence" was taught by Jesus in the priestly prayer: "That they may all be one, as thou, Father, art in me, and I in thee, that they also may be one in us" (Jn 17:21).
BIBL.: sources
Chaillet, Paris 1939; E. Morsch, Le Corps Mystique du Christ, 2 vols., 2nd ed., Brussels 1936; id., La théol. du Corps Mystique, 2 vols., Paris-Brussels 1944; L. Cerfaux, La Théologie de l'Eglise suivant 1st Paul (Collection Unam Sanctam, 10), 2nd ed., Paris 1948; N. Flew, The Nature of the Church. Papers presented to the Theological Commission appointed by the Continuation Committee of the World Conference on Faith and Order, London 1952, Bernardo Schultze.