As the week for Christian unity draws to a close - over the hubbub of insipid niceties and empty words - let us recall the doctrinal lessons on true unity in the Catholic Church. Pope Francis, drawing on the nearly complete text of what would have been the third encyclical by the venerable Pope Benedict XVI, promulgated in Lumen Fidei the following:
The unity and integrity of faith
47. The unity of the Church in time and space is linked to the unity of the faith: "there is one body and one Spirit… one faith" (Eph 4:4-5). These days we can imagine a group of people being united in a common cause, in mutual affection, in sharing the same destiny and a single purpose. But we find it hard to conceive of a unity in one truth. We tend to think that a unity of this sort is incompatible with freedom of thought and personal autonomy. Yet the experience of love shows us that a common vision is possible, for through love we learn how to see reality through the eyes of others, not as something which impoverishes but instead enriches our vision. Genuine love, after the fashion of God’s love, ultimately requires truth, and the shared contemplation of the truth which is Jesus Christ enables love to become deep and enduring. This is also the great joy of faith: a unity of vision in one body and one spirit. Saint Leo the Great could say: "If faith is not one, then it is not faith".
What is the secret of this unity? Faith is "one", in the first place, because of the oneness of the God who is known and confessed. All the articles of faith speak of God; they are ways to know him and his works. Consequently, their unity is far superior to any possible construct of human reason. They possess a unity which enriches us because it is given to us and makes us one.
Faith is also one because it is directed to the one Lord, to the life of Jesus, to the concrete history which he shares with us. Saint Irenaeus of Lyons made this clear in his struggle against Gnosticism.
The Gnostics held that there are two kinds of faith: a crude, imperfect faith suited to the masses, which remained at the level of Jesus’ flesh and the contemplation of his mysteries; and a deeper, perfect faith reserved to a small circle of initiates who were intellectually capable of rising above the flesh of Jesus towards the mysteries of the unknown divinity. In opposition to this claim, which even today exerts a certain attraction and has its followers, Saint Irenaeus insisted that there is but one faith, for it is grounded in the concrete event of the incarnation and can never transcend the flesh and history of Christ, inasmuch as God willed to reveal himself fully in that flesh. For this reason, he says, there is no difference in the faith of "those able to discourse of it at length" and "those who speak but little", between the greater and the less: the first cannot increase the faith, nor the second diminish it.
Finally, faith is one because it is shared by the whole Church, which is one body and one Spirit. In the communion of the one subject which is the Church, we receive a common gaze. By professing the same faith, we stand firm on the same rock, we are transformed by the same Spirit of love, we radiate one light and we have a single insight into reality.
48. Since faith is one, it must be professed in all its purity and integrity. Precisely because all the articles of faith are interconnected, to deny one of them, even of those that seem least important, is tantamount to distorting the whole. Each period of history can find this or that point of faith easier or harder to accept: hence the need for vigilance in ensuring that the deposit of faith is passed on in its entirety (cf. 1 Tim 6:20) and that all aspects of the profession of faith are duly emphasized. Indeed, inasmuch as the unity of faith is the unity of the Church, to subtract something from the faith is to subtract something from the veracity of communion. The Fathers described faith as a body, the body of truth composed of various members, by analogy with the body of Christ and its prolongation in the Church. The integrity of the faith was also tied to the image of the Church as a virgin and her fidelity in love for Christ her spouse; harming the faith means harming communion with the Lord. The unity of faith, then, is the unity of a living body; this was clearly brought out by Blessed John Henry Newman when he listed among the characteristic notes for distinguishing the continuity of doctrine over time its power to assimilate everything that it meets in the various settings in which it becomes present and in the diverse cultures which it encounters, purifying all things and bringing them to their finest expression. Faith is thus shown to be universal, catholic, because its light expands in order to illumine the entire cosmos and all of history.
49. As a service to the unity of faith and its integral transmission, the Lord gave his Church the gift of apostolic succession. Through this means, the continuity of the Church’s memory is ensured and certain access can be had to the wellspring from which faith flows. The assurance of continuity with the origins is thus given by living persons, in a way consonant with the living faith which the Church is called to transmit. She depends on the fidelity of witnesses chosen by the Lord for this task. For this reason, the magisterium always speaks in obedience to the prior word on which faith is based; it is reliable because of its trust in the word which it hears, preserves and expounds. In Saint Paul’s farewell discourse to the elders of Ephesus at Miletus, which Saint Luke recounts for us in the Acts of the Apostles, he testifies that he had carried out the task which the Lord had entrusted to him of "declaring the whole counsel of God" (Acts 20:27). Thanks to the Church’s magisterium, this counsel can come to us in its integrity, and with it the joy of being able to follow it fully.