Christ endowed the Church, his body, with the fullness of the benefits and means of salvation. The Holy Spirit dwells in her, enlivens her with his gifts and charisms, sanctifies, guides and constantly renews her. The result is a unique and special relationship which, while not excluding the action of Christ and the Spirit outside the Church’s visible boundaries, confers upon her a specific and necessary role; hence the Church’s special connection with the kingdom of God and of Christ, which she has ‘the mission of announcing and inaugurating among all peoples’ (Lumen Gentium, 5). (John Paul II, Encyclical Redemptoris Missio, no. 11, December 7, 1990)

But we also know that the modern world is in the grip of change and upheaval. It is undergoing developments which are having a profound influence on its outward way of life and habits of thought. The great advances made in science, technology, and social life, and the various currents of philosophical and political thought pervading modern society, are greatly influencing men’s opinions and their spiritual and cultural pursuits. The Church itself is being engulfed and shaken by this tidal wave of change, for however much men may be committed to the Church, they are deeply affected by the climate of the world. They run the risk of becoming confused, bewildered and alarmed, and this is a state of affairs which strikes at the very roots of the Church. It drives many people to adopt the most outlandish views. […] An effective remedy is needed if all these dangers, which are prevalent in many quarters, are to be obviated, and We believe that such a remedy is to be found in an increased self-awareness on the part of the Church. The Church must get a clearer idea of what it really is in the mind of Jesus Christ as recorded and preserved in Sacred Scripture and in Apostolic Tradition, and interpreted and explained by the tradition of the Church under the inspiration and guidance of the Holy Spirit. (Paul VI. Encyclical Ecclesiam suam, no. 26, August 6, 1964)

But the danger remains. Indeed, the worker in the apostolate is under constant fire. The desire to come together as brothers must not lead to a watering down or whittling away of truth. Our dialogue must not weaken our attachment to our faith. Our apostolate must not make vague compromises concerning the principles which regulate and govern the profession of the Christian faith both in theory and in practice. An immoderate desire to make peace and sink differences at all costs (irenism and syncretism) is ultimately nothing more than skepticism about the power and content of the Word of God which we desire to preach. The effective apostle is the man who is completely faithful to Christ’s teaching. He alone can remain unaffected by the errors of the world around him, the man who lives his Christian life to the full. (Paul VI. Encyclical Ecclesiam suam, no. 88, August 6, 1964)

There exists an institution able to safeguard the sanctity of the law of nations. This institution is a part of every nation; at the same time it is above all nations. She enjoys, too, the highest authority, the fullness of the teaching power of the Apostles. Such an institution is the Church of Christ. She alone is adapted to do this great work, for she is not only divinely commissioned to lead mankind, but moreover, because of her very make-up and the constitution which she possesses, by reason of her age-old traditions and her great prestige, which has not been lessened but has been greatly increased since the close of the War, cannot but succeed in such a venture where others assuredly will fail. It is apparent from these considerations that true peace, the peace of Christ, is impossible unless we are willing and ready to accept the fundamental principles of Christianity, unless we are willing to observe the teachings and obey the law of Christ, both in public and private life. If this were done, then society being placed at last on a sound foundation, the Church would be able, in the exercise of its divinely given ministry and by means of the teaching authority which results therefrom, to protect all the rights of God over men and nations. […] The true peace of Christ can only exist in the Kingdom of Christ – ‘the peace of Christ in the Kingdom of Christ.’ It is no less unquestionable that, in doing all we can to bring about the re-establishment of Christ’s kingdom, we will be working most effectively toward a lasting world peace. (Pius XI. Encyclical Ubi arcano, December 23, 1922)

The universal Church cannot err, since she is governed by the Holy Ghost, Who is the Spirit of truth: for such was Our Lord’s promise to His disciples (Jn. 16:13): ‘When He, the Spirit of truth, is come, He will teach you all truth.’ (Saint Thomas Aquinas. Summa Theologica II–II, q. 1, a. 9)

These pan-Christians who turn their minds to uniting the churches seem, indeed, to pursue the noblest of ideas in promoting charity among all Christians: nevertheless how does it happen that this charity tends to injure faith? Everyone knows that John himself, the Apostle of love, who seems to reveal in his Gospel the secrets of the Sacred Heart of Jesus, and who never ceased to impress on the memories of his followers the new commandment ‘Love one another,’ altogether forbade any intercourse with those who professed a mutilated and corrupt version of Christ’s teaching: ‘If any man come to you and bring not this doctrine, receive him not into the house nor say to him: God speed you’ (2 Jn 10). For which reason, since charity is based on a complete and sincere faith, the disciples of Christ must be united principally by the bond of one faith. (Pius XI. Encyclical Mortalium animos, no. 9, January 6, 1928)

In these times of confusion and disorder, it is not unusual to see Christians, Catholics – even within the secular clergy and cloisters – who constantly have a word of conformity, of conciliation and negotiation on their lips. Very well! I do not hesitate to declare: these men are in error, and do not consider them to be the lesser enemies of the Church. We live in a corrupt and pestilent atmosphere and we must know how to preserve ourselves from it. Let us not allow ourselves to be contaminated by false doctrines, which lose all things under the pretext of saving all. (Pius IX. Address in the Church of Aracoeli, September 17, 1861)

But, God forbid that the sons of the Catholic Church ever in any way be hostile to those who are not joined with us in the same bonds of faith and love; but rather they should always be zealous to seek them out and aid them, whether poor, or sick, or afflicted with any other burdens, with all the offices of Christian charity; and they should especially endeavor to snatch them from the darkness of error in which they unhappily lie, and lead them back to Catholic truth and to the most loving Mother the Church, who never ceases to stretch out her maternal hands lovingly to them, and to call them back to her bosom so that, established and firm in faith, hope, and charity, and ‘being fruitful in every good work’ (Col 1:10), they may attain eternal salvation. (Denzinger-Hünermann 2865–2867. Pius IX, Encyclical Quanto conficiamur moerore, August 10, 1863)

Man’s relations with foreigners are twofold: peaceful, and hostile. […] The reason for this was that if foreigners were allowed to meddle with the affairs of a nation as soon as they settled down in its midst, many dangers might occur, since the foreigners not yet having the common good firmly at heart might attempt something hurtful to the people. (Saint Thomas Aquinas. Summa Theologica I–II, q. 105, a. 3)

Communication with a particular person is forbidden to the faithful, in two ways: first, as a punishment of the person with whom they are forbidden to communicate; secondly, for the safety of those who are forbidden to communicate with others. Both motives can be gathered from the Apostle’s words (1Cor 5:6). […] With regard to the second way, it seems that one ought to distinguish according to the various conditions of persons, circumstances and time. For some are firm in the faith; and so it is to be hoped that their communicating with unbelievers will lead to the conversion of the latter rather than to the aversion of the faithful from the faith. These are not to be forbidden to communicate with unbelievers who have not received the faith, such as pagans or Jews, especially if there be some urgent necessity for so doing. But in the case of simple people and those who are weak in the faith, whose perversion is to be feared as a probable result, they should be forbidden to communicate with unbelievers, and especially to be on very familiar terms with them, or to communicate with them without necessity. (Saint Thomas Aquinas. Summa Theologica II–II, q. 10, a. 9)

Islam is currently expanding rapidly, particularly due to migratory movements from countries with rapid demographic growth. Countries with a Christian tradition, where, except in Africa, population growth is slower or even negative, often see the increased presence of Muslims as a social, cultural or even religious challenge. […] True collaboration with Muslims on the level of culture in real reciprocity may foster fruitful relationships in Islamic countries and with Muslim communities established in traditionally Christian countries. Such collaboration does not dispense Christians from bearing witness to their Christological and Trinitarian faith in relation to other expressions of monotheism. (Pontifical Council for Culture. Towards a Pastoral approach to culture, May 23, 1999)

Let all remember that the flood of evil and disaster that has over-taken the world in past years was due chiefly to the fact that the divine religion of Jesus Christ, that provider of mutual charity among citizens, peoples and nations, did not govern, as it should, private, domestic and public life. If things have gone wrong on account of the desertion from Christ, public and private life must return to Him as soon as possible: if error has clouded the minds of men, they must return to that truth which, revealed from on high, indicates the right way to heaven: if hatred has brought them fatal results, they must return to Christian love which alone can heal their many wounds, and carry them over the crisis so filled with danger. (Pius XII. Encylcial Optatissima pax, no. 8, December 18, 1947)

However, the Church’s ‘missionary proclamation is endangered today by relativistic theories which seek to justify religious pluralism, not only de facto but also de iure (or in principle)’ (cf. Dominus Jesus, no.4). For a long time, the reason for evangelization has not been clear to many among the Catholic faithful (Evangelii Nuntiadi, no. 80). It is even stated that the claim to have received the gift of the fullness of God’s revelation masks an attitude of intolerance and a danger to peace. (Congregation for the Doctrine of the Faith, Doctrinal Note on Some Aspects of Evangelization, December 3, 2007)

We cannot, however, forget the transcendence of the Gospel in relation to all human cultures in which the Christian faith has the vocation to root itself and come to fruition according to all its potentialities. However great the respect should be for what is true and holy in the cultural heritage of a people, this attitude does not demand that one should lend an absolute character to this cultural heritage. No one can forget that, from the beginning, the Gospel was a ‘scandal for the Jews and foolishness for the pagans’ (1Cor 1:23). Inculturation which borrows the way of dialogue between religions cannot in any way pledge itself to syncretism. (International Theological Commission. Faith and inculturation, no. 14, December 1987)

The underlying question concerns the relationship between the Church and the world. […] The advanced secularization of society brings with it a tendency to blur the boundaries between the Church and the world. Certain aspects of the prevailing culture are allowed to condition the Christian community in ways which the Gospel does not permit. […] This often goes hand in hand with an uncritical approach to the problem of moral evil, and a reluctance to recognize the reality of sin and the need for forgiveness. This attitude embodies a too optimistic view of modernity, together with an uneasiness about the Cross and its implications for Christian living. The past is too easily dismissed, and the horizontal is so stressed that the sense of the supernatural grows weak. (John Paul II. Address to the Bishops of Australia on their ad limina visit, no. 3, December 14, 1998)

The Church’s task is described as though it had to proceed in two directions: on the one hand promoting such ‘values of the kingdom’ as peace, justice, freedom, brotherhood, etc., while on the other hand fostering dialogue between peoples, cultures and religions, so that through a mutual enrichment they might help the world to be renewed and to journey ever closer toward the kingdom. Together with positive aspects, these conceptions often reveal negative aspects as well. First, they are silent about Christ: the kingdom of which they speak is ‘theocentrically’ based, since, according to them, Christ cannot be understood by those who lack Christian faith, whereas different peoples, cultures and religions are capable of finding common ground in the one divine reality, by whatever name it is called. For the same reason they put great stress on the mystery of creation, which is reflected in the diversity of cultures and beliefs, but they keep silent about the mystery of redemption. Furthermore, the kingdom, as they understand it, ends up either leaving very little room for the Church or undervaluing the Church in reaction to a presumed ‘ecclesiocentrism’ of the past, and because they consider the Church herself only a sign, for that matter a sign not without ambiguity. (John Paul II, Encyclical Redemptoris Missio, no. 17, December 7, 1990)

The kingdom of God is not a concept, a doctrine, or a program subject to free interpretation, but it is before all else a person with the face and name of Jesus of Nazareth, the image of the invisible God. If the kingdom is separated from Jesus, it is no longer the kingdom of God which he revealed. The result is a distortion of the meaning of the kingdom, which runs the risk of being transformed into a purely human or ideological goal, and a distortion of the identity of Christ, who no longer appears as the Lord to whom everything must one day be subjected (cf. 1Cor 15:27). Likewise, one may not separate the kingdom from the Church. It is true that the Church is not an end unto herself, since she is ordered toward the kingdom of God of which she is the seed, sign and instrument. Yet, while remaining distinct from Christ and the kingdom, the Church is indissolubly united to both. Christ endowed the Church, his body, with the fullness of the benefits and means of salvation. The Holy Spirit dwells in her, enlivens her with his gifts and charisms, sanctifies, guides and constantly renews her. The result is a unique and special relationship which, while not excluding the action of Christ and the Spirit outside the Church’s visible boundaries, confers upon her a specific and necessary role; hence the Church’s special connection with the kingdom of God and of Christ, which she has ‘the mission of announcing and inaugurating among all peoples’ (Lumen Gentium, 5). (John Paul II, Encyclical Redemptoris Missio, no. 18, December 7, 1990)

Wherefore this people, while remaining one and only one, is to be spread throughout the whole world and must exist in all ages. […] It follows that though there are many nations there is but one people of God, which takes its citizens from every race, making them citizens of a kingdom which is of a heavenly rather than of an earthly nature. All the faithful, scattered though they be throughout the world, are in communion with each other in the Holy Spirit. […] Since the kingdom of Christ is not of this world the Church or people of God in establishing that kingdom takes nothing away from the temporal welfare of any people. On the contrary it fosters and takes to itself, insofar as they are good, the ability, riches and customs in which the genius of each people expresses itself. […] This characteristic of universality which adorns the people of God is a gift from the Lord Himself. By reason of it, the Catholic Church strives constantly and with due effect to bring all humanity and all its possessions back to its source in Christ, with Him as its head and united in His Spirit. (Vatican Council II. Dogmatic constitution Lumen gentium, no. 13, November 21, 1964)

In virtue of this catholicity each individual part contributes through its special gifts to the good of the other parts and of the whole Church. Through the common sharing of gifts and through the common effort to attain fullness in unity, the whole and each of the parts receive increase. Not only, then, is the people of God made up of different peoples but in its inner structure also it is composed of various ranks. This diversity among its members arises either by reason of their duties, as is the case with those who exercise the sacred ministry for the good of their brethren, or by reason of their condition and state of life, as is the case with those many who enter the religious state and, tending toward holiness by a narrower path, stimulate their brethren by their example. […] Between all the parts of the Church there remains a bond of close communion whereby they share spiritual riches, apostolic workers and temporal resources. […] All men are called to be part of this catholic unity of the people of God. (Vatican Council II. Dogmatic constitution Lumen gentium, no. 13, November 21, 1964)

The lay apostolate, however, is a participation in the salvific mission of the Church itself. Through their baptism and confirmation all are commissioned to that apostolate by the Lord Himself. […] Now the laity are called in a special way to make the Church present and operative in those places and circumstances where only through them can it become the salt of the earth. Thus every layman, in virtue of the very gifts bestowed upon him, is at the same time a witness and a living instrument of the mission of the Church itself ‘according to the measure of Christ’s bestowal’ (Eph 4:7). (Vatican Council II. Dogmatic constitution Lumen gentium, no. 13, November 21, 1964)

Pressed on to Our intent by Charity, that hastens fastest there where the need is greatest, We direct Our first thoughts to those most unfortunate of all nations who have never received the light of the Gospel, or who, after having possessed it, have lost it through neglect or the vicissitudes of time: Hence do they ignore God, and live in the depths of error. Now, as all salvation comes from Jesus Christ – for there is no other Name under Heaven given to men whereby we must be saved – Our ardent desire is that the most Holy Name of Jesus should rapidly pervade and fill every land. (Leo XIII. Encyclical Praeclara gratulationis, June 20, 1894)

We mean a perfect and complete union, such as could not subsist in any way if nothing else was brought about but a certain kind of agreement in the Tenets of Belief and an intercourse of Fraternal love. The True Union between Christians is that which Jesus Christ, the Author of the Church, instituted and desired, and which consists in a Unity of Faith and Unity of Government. (Leo XIII. Encyclical Praeclara gratulationis, June 20, 1894)

On this subject we need but recall for one moment the examples recorded in history. Of these facts there cannot be any shadow of doubt: for instance, that civil society was renovated in every part by Christian institutions; that in the strength of that renewal the human race was lifted up to better things – nay, that it was brought back from death to life, and to so excellent a life that nothing more perfect had been known before, or will come to be known in the ages that have yet to be. Of this beneficent transformation Jesus Christ was at once the first cause and the final end; as from Him all came, so to Him was all to be brought back. (Leo XIII. Encyclical Rerum novarum, no. 21, May 15, 1891)

Indeed, the Church, guided by charity and respect for freedom, must be primarily committed to proclaiming to all people the truth definitively revealed by the Lord, and to announcing the necessity of conversion to Jesus Christ and of adherence to the Church through Baptism and the other sacraments, in order to participate fully in communion with God, the Father, Son and Holy Spirit. (Congregation for the Doctrine of the Faith. Dominus Iesus, no. 22, August 6, 2000)

Indeed, in the piety of the people of America there are oftentimes many elements at odds with Christianity. These elements occasionally lead to a syncretism constructed on the basis of popular beliefs, or, in some cases, they cause believers to become disoriented and easily led astray by sects or para-religious movements. […] A secular mentality can also be detected in the matter of religion. Such an attitude is gradually leading people to moral relativism or religious indifference. […] The increasing religious indifference leads to the loss of the sense of God and of His holiness, which, in turn, is translated into a loss of a sense of the sacred, of mystery and of the capacity for wonder. These are human dispositions which predispose a person to dialogue and to an encounter with God. Such indifference almost inevitably leads to a false moral autonomy and a secularistic life-style which excludes God. (Synod of Bishops. Lineament of the Special Assembly for America, no. 18–19, August 1, 1996)