Christ clearly called his disciples to unity, so that all may believe (cf. Jn 17:21). In God's plan, the unity of all Christians, gathered together by the Spirit, was to reflect the unity of the Father and the Son, united by the same Spirit. But Christian unity has been undermined over the centuries: to a division between Catholics and Orthodox, in the year 1053 AD, was added a division between Catholics and Protestants, at the beginning of the 16th century. It is true that much work has been done to restore unity over the past hundred years, but many obstacles still prevent the return of the undivided Church.
Unity is the sign of good community health. It has a value in itself, because it is an actualization of the supernatural love that keeps the faithful together. It also has (or would have had) a prophetic function, because it reflects (or would have reflected) the unity of the gospel message, making it clearer for all. The disunity of Christians, on the contrary, makes evident the discordance between the discourses of the different Churches, and makes less clear the message we are called to spread throughout the world.
For the love of the people whom we seek to gather in God, we must therefore work for Christian unity. But this outreach risks being compromised today by divisions within the Churches themselves, split between different tendencies. Working for Christian unity can therefore only be done today by keeping in mind the challenge of internal unity. To disregard this challenge is to risk building on sand. Churches that want to serve as a “material” for the building of unity must be as solid as rock.
Working for Christian unity thus implies, at the same time, ensuring the unity of one's Church, which is particularly difficult at this time. However, we Catholics are blessed to have received, preserved and developed, according to God's will, the Petrine ministry, which is a source and a principle of unity. Around the Pope, Peter's successor, and in communion with the bishops, the successors of the apostles, unity is achieved. This is because the Pope has received a mandate from Christ Jesus to strengthen his brothers in the one Catholic faith (cf. Lk 22:32).
What does it mean, exactly, to "strengthen in faith"? It means to anchor the believer in the supernaturally revealed and lived knowledge of the true God manifested in Jesus Christ. This anchoring is ensured first of all by baptism, which gives us the Spirit of God, and thus the supernatural ability to understand God's revelation with God's understanding. "No one comprehends the thoughts of God except the Spirit of God," Paul says. "Now we have received not the spirit of the world, but the spirit which is from God, that we might understand the gifts bestowed on us by God.” (1 Cor 2:11-12)
But we know that baptism is only one step in the appropriation of the deposit of faith. Then comes the conscious and sustained effort to grow in the knowledge and love of God, through the reception of a solid catechetical teaching, irrigated by the prayer of the one who gives it as much as by that of the one who receives it. Obviously, this teaching proves its fruitfulness when it leads us to live uprightly and impels us to give ourselves to others, in a spirit of charity and service, both in the world and within the Church.
Thanks to an integral and ongoing formation based on the meditation of the Word that shapes the intelligence and the will, Christians find the truly supernatural capacity to go to the Temple "with one accord" (Acts 2:46), that is, to live and celebrate in the unity of the true faith - a faith constantly renewed at the sources of the sacraments, which are the usual means by which Jesus communicates his life to us. Clearly, integral and ongoing formation drives away the continuous risk of intellectual and moral deformation.
The effort for Christian unity begins, so to speak, at home, I mean in our own Church, whose authentically Christian wisdom we must appropriate, which alone can preserve us from moral and doctrinal deviations. In fact, rootedness in the apostolic tradition confirmed by Peter conditions our ability to embody the religion received from Jesus Christ and understood at the same time as a theology, a cult, an ethic and a spirituality enlivened by grace and manifested in active charity.
Christian unity therefore depends, first of all, within our Church, on the quality of the transmission of the deposit of faith and on the learning of the Christian virtues. It depends on the quality of Christian education and, of course, on the supernatural love that drives the ecclesial effort of transmission. “For apart from him we can do nothing” (cf. Jn 15:5). Him being, of course, the risen Christ, who teaches through the mouth of this enthusiastic priest, or who gives himself as a model to be imitated in the exemplarity of that devoted lay person, etc.
The theme of the Week of Prayer for Christian Unity 2021 is "Abide in my love and you shall bear much fruit" (cf. John 15:5-9). It reminds us that the fruit of unity will come only if we know how to expose ourselves to God's love and rest in him. This love is also communicated to us through the teaching of revealed truth, which the Church has the custody of. The study, meditation and deepening of the Catholic tradition is therefore offered to us as a path to unity. Internal unit, first, and, after that, external unit.
This effort to assimilate the deposit of faith will not simply lead to a familiarization with dogmatic formulas, whose function is to normatively define the content of Christian doctrine. The learning of "a common language of faith, normative for all and uniting all in the same confession of faith" (Catechism of the Catholic Church, 185) is certainly an obligatory stage for those who truly want to commune with other Christians. But, as a system of signs, this language points to a reality, and it is because it gives us real and mysterious access to this supernatural reality that it is so dear to us.
Surely, the common language of the Church can somewhat put us off. The technical terms of theology may seem too abstract to us. The very abstruseness of certain passages of Scripture (from which the Church's teaching is drawn) can discourage us from ever understanding anything. But to begin to see more clearly, we must remember that these truths of faith have been conquered in and through prayer, and that it is through prayer alone that they will be revealed to us as they are, that is, as sources of life.
Under the guidance of the Spirit of Truth, the strangest pages of the Bible suddenly reveal themselves to be of unprecedented depth and richness. And to more than mere transcendent truths, the dogmas, illuminated from within by the Spirit, give us access to the Transcendent itself. They root us in it, so that we can bear fruit. It is by this rooting in God, made possible by the revealed Word and the Spirit poured out, that we can most effectively work for the great cause of Christian unity.