8. Vatican II and ecumenism

Introduction
The Second Vatican Council, more commonly known as Vatican II, is the 21st ecumenical council recognized by the Roman Catholic Church. It meets from 11th October 1962 to 8th December 1965 during the pontificates of John XXIII (1958-1963) and Paul VI (1963-1978), and aims to undertake an aggiornamento of the Catholic Church. If the Council makes for a relative modernization of the Catholic Church as well as an opening to the world, it faces conflicting criticisms: from the traditionalists, who reject what they perceive as a departure from the Tradition, as well as from the progressive side, regretting that the modernization of the Church didn't go further.
Source 1

Encyclical Ecclesiam suam

Ecclesiam sua is an encyclical published by Pope Paul VI (1963-1978) on 6th August 1964. Published during the last year of the Second Vatican Council, its purpose is to clarify the main objectives of this Council. Unlike other texts published during the Council, it is written by the pope, not by the Council Fathers.

“Our intense desire is to see the Church become what Christ intended it to be: one, holy, and entirely dedicated to the pursuit of that perfection to which Christ called it and for which He qualified it. In its pilgrimage through the world the Church must really strive to manifest that ideal of perfection envisaged for it by the divine Redeemer […].
The very external conditions in which the Church finds itself give added impetus to this striving for religious and moral perfection, for the Church cannot remain indifferent to or unaffected by the changes which take place in the world around. They influence, modify, and condition its course of action in all sorts of ways. As we know, the Church does not exist in isolation from the world. It lives in the world, and its members are consequently influenced and guided by the world. They imbibe its culture, are subject to its laws and adopt its customs. This intimate contact with the world is continually creating problems for the Church and at the present time these problems are extremely acute. The Christian life, as encouraged and preserved by the Church, must resist every possible source of deception, contamination, or restriction of its freedom. It must guard against these things as it would guard against contamination by error or evil. Yet at the same time it must not only adapt itself to the forms of thought and living which a temporal environment induces, one might almost say imposes, on it-provided, of course, such forms are not incompatible with the basic principles of its religious and moral teaching-but it must also strive to approach these forms and to correct, ennoble, encourage, and sanctify them. And this demands of the Church a continual process of self-examination and re-appraisal of its external conduct. This in fact is what the present era is demanding of the Church with such insistence and earnestness […].
It will be for the Council, naturally, to decide what reforms are to be introduced into the Church's legislation and discipline. The post-conciliar committees, or commissions-especially the Commission for the Revision of Canon Law, which has already been set up-will concern themselves with the task of formulating in concrete terms the recommendations of the Ecumenical Synod. It will be your duty, therefore, Venerable Brethren, to indicate to us what decisions are required for purifying and rejuvenating the Church's image. Let Us, for Our part, give public expression once again to this resolve of Ours to do all We can to sponsor this reform […].
First We must lay down a few rules to guide us in the work of reform. Obviously, there can be no question of reforming the essential nature of the Church or its basic and necessary structure. To use the word reform in that context would be to misuse it completely. We cannot brand the holy and beloved Church of God with the mark of infidelity. We must consider our membership in it as one of our greatest blessings. It testifies to our spirit "that we are the children of God." (Rom 8. 16.) […].
In this context, therefore, when we speak about reform we are not concerned to change things, but to preserve all the more resolutely the characteristic features which Christ has impressed on His Church. Or rather, we are concerned to restore to the Church that ideal of perfection and beauty that corresponds to its original image […].
We must strengthen these convictions in ourselves if we are also to avoid another danger which the desire for reform can produce, not so much in us pastors, who are restrained by the proper awareness of our sacred duty, as in many of the faithful, who think that the reform of the Church should consist principally in adapting its way of thinking and acting to the customs and temper of the modern secular world. The fascination of worldly life today is very powerful indeed, and many people regard conformity to it as an inescapable and indeed a wise course to take. Hence, those who are not deeply rooted in the faith and in the observance of the Church's laws, readily imagine that the time is ripe to adjust themselves to worldly standards of living, on the assumption that these are the best and only possible ones for a Christian to adopt. This craving for uniformity is observable even in the realm of philosophy (it is extraordinary how much weight is attached to fashion in a province where the mind ought to be free and independent, anxious only to arrive at the truth, and bowing to the authority of none but proved masters). It is observable also in the realm of ethics, making it more and more perplexing and difficult to define moral rectitude and the right conduct of life […].
We must be in the world, but not of it. These important words of Christ are especially relevant at the present time, difficult though they may be to put into practice […].
The purpose of this exhortation of Ours is not to lend substance to the belief that perfection consists in rigidly adhering to the methods adopted by the Church in the past and refusing to countenance the practical measures commonly thought to be in accord with the character of our time. These measures can be put to the test. We cannot forget Pope John XXIII's word aggiornamento which We have adopted as expressing the aim and object of Our own pontificate. Besides ratifying it and confirming it as the guiding principle of the Ecumenical Council, We want to bring it to the notice of the whole Church. It should prove a stimulus to the Church to increase its ever growing vitality and its ability to take stock of itself and give careful consideration to the signs of the times, always and everywhere "proving all things and holding fast that which is good" (1 Thes 5. 21.) with the enthusiasm of youth.”

Encyclical Ecclesiam suam.
http://www.vatican.va/holy_father/paul_vi/encyclicals/documents/hf_p-vi_enc_06081964_ecclesiam_en.html

Source 2a

Decree on ecumenism

Unitatis redintegratio (restoration of Unity), the Decree on Ecumenism, was adopted by the Second Vatican Council on 21th November 1964 with 2137 votes against 11. It constitutes an important shift in the relationship between the Catholic Church and other Christian denominations. Indeed, rather than seeing them as Christians in the wrong, Unitatis redintegratio encourages the opening of a dialogue with the hope to facilitate mutual understanding. That being said, it still understands Christian Unity as the result of guiding the "separated brethren" back into the Roman fold.

“The restoration of unity among all Christians is one of the principal concerns of the Second Vatican Council. Christ the Lord founded one Church and one Church only. However, many Christian communions present themselves to men as the true inheritors of Jesus Christ; all indeed profess to be followers of the Lord but differ in mind and go their different ways, as if Christ Himself were divided. Such division openly contradicts the will of Christ, scandalizes the world, and damages the holy cause of preaching the Gospel to every creature […].
Even in the beginnings of this one and only Church of God there arose certain rifts, which the Apostle strongly condemned. But in subsequent centuries much more serious dissensions made their appearance and quite large communities came to be separated from full communion with the Catholic Church - for which, often enough, men of both sides were to blame. The children who are born into these Communities and who grow up believing in Christ cannot be accused of the sin involved in the separation, and the Catholic Church embraces upon them as brothers, with respect and affection. For men who believe in Christ and have been truly baptized are in communion with the Catholic Church even though this communion is imperfect. The differences that exist in varying degrees between them and the Catholic Church - whether in doctrine and sometimes in discipline, or concerning the structure of the Church - do indeed create many obstacles, sometimes serious ones, to full ecclesiastical communion. The ecumenical movement is striving to overcome these obstacles. But even in spite of them it remains true that all who have been justified by faith in Baptism are members of Christ's body, and have a right to be called Christian, and so are correctly accepted as brothers by the children of the Catholic Church […].
The term "ecumenical movement" indicates the initiatives and activities planned and undertaken, according to the various needs of the Church and as opportunities offer, to promote Christian unity. These are: first, every effort to avoid expressions, judgments and actions which do not represent the condition of our separated brethren with truth and fairness and so make mutual relations with them more difficult; then, "dialogue" between competent experts from different Churches and Communities. At these meetings, which are organized in a religious spirit, each explains the teaching of his Communion in greater depth and brings out clearly its distinctive features. In such dialogue, everyone gains a truer knowledge and more just appreciation of the teaching and religious life of both Communions […].
We must get to know the outlook of our separated brethren. To achieve this purpose, study is of necessity required, and this must be pursued with a sense of realism and good will. Catholics, who already have a proper grounding, need to acquire a more adequate understanding of the respective doctrines of our separated brethren, their history, their spiritual and liturgical life, their religious psychology and general background. Most valuable for this purpose are meetings of the two sides - especially for discussion of theological problems - where each can deal with the other on an equal footing - provided that those who take part in them are truly competent and have the approval of the bishops. From such dialogue will emerge still more clearly what the situation of the Catholic Church really is. In this way too the outlook of our separated brethren will be better understood, and our own belief more aptly explained.”

Decree on ecumenism..
http://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_decree_19641121_unitatis-redintegratio_en.html

Source 2b

Declaration on the relations of the Church the non-Christian religions

The Declaration on the Relations of the Church with Non-Christian Religions Nostra ætate (In our Time) was adopted by the Second Vatican Council on 28th October 1965 with 2221 votes to 88, and 1 null vote. It goes beyond ecumenism by promoting interreligious dialogue. Nostra Aetate emphasizes what brings together these separate religions and encourages the development of common spiritual values. It points out the elements shared with other monotheistic religions, in particular ly the same faith in the God of Abraham. It stresses the fact that Christianity comes from Judaism and rejects any form of anti-semitism. On the subject of Islam, this declaration suggests forgetting past conflicts and highlighting common values instead.

“From ancient times down to the present, there is found among various peoples a certain perception of that hidden power which hovers over the course of things and over the events of human history; at times some indeed have come to the recognition of a Supreme Being, or even of a Father. This perception and recognition penetrates their lives with a profound religious sense […].The Catholic Church rejects nothing that is true and holy in these religions. She regards with sincere reverence those ways of conduct and of life, those precepts and teachings which, though differing in many aspects from the ones she holds and sets forth, nonetheless often reflect a ray of that Truth which enlightens all men. Indeed, she proclaims, and ever must proclaim Christ […].
The Church regards with esteem also the Moslems. They adore the one God, living and subsisting in Himself; merciful and all- powerful, the Creator of heaven and earth, who has spoken to men; they take pains to submit wholeheartedly to even His inscrutable decrees, just as Abraham, with whom the faith of Islam takes pleasure in linking itself, submitted to God […]. Since in the course of centuries not a few quarrels and hostilities have arisen between Christians and Moslems, this sacred synod urges all to forget the past and to work sincerely for mutual understanding and to preserve as well as to promote together for the benefit of all mankind social justice and moral welfare, as well as peace and freedom.
As the sacred synod searches into the mystery of the Church, it remembers the bond that spiritually ties the people of the New Covenant to Abraham's stock. Thus the Church of Christ acknowledges that, according to God's saving design, the beginnings of her faith and her election are found already among the Patriarchs, Moses and the prophets. She professes that all who believe in Christ -Abraham's sons according to faith - are included in the same Patriarch's call, and likewise that the salvation of the Church is mysteriously foreshadowed by the chosen people's exodus from the land of bondage. The Church, therefore, cannot forget that she received the revelation of the Old Testament through the people with whom God in His inexpressible mercy concluded the Ancient Covenant […].
Since the spiritual patrimony common to Christians and Jews is thus so great, this sacred synod wants to foster and recommend that mutual understanding and respect which is the fruit, above all, of biblical and theological studies as well as of fraternal dialogues. True, the Jewish authorities and those who followed their lead pressed for the death of Christ; still, what happened in His passion cannot be charged against all the Jews, without distinction, then alive, nor against the Jews of today. Although the Church is the new people of God, the Jews should not be presented as rejected or accursed by God, as if this followed from the Holy Scriptures. All should see to it, then, that in catechetical work or in the preaching of the word of God they do not teach anything that does not conform to the truth of the Gospel and the spirit of Christ. Furthermore, in her rejection of every persecution against any man, the Church, mindful of the patrimony she shares with the Jews and moved not by political reasons but by the Gospel's spiritual love, decries hatred, persecutions, displays of anti-Semitism, directed against Jews at any time and by anyone.”

Declaration on the relations of the Church the non-Christian religions.
http://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_decl_19651028_nostra-aetate_en.html