Unity is the central focus of Pope Leo XIV’s vision. That was made obvious in his homily at his inauguration, but it goes back long before that, for he chose as his episcopal motto, In Illo uno unum, which means “In the One, we are one.” It is taken from St. Augustine’s meditation on Psalm 127, where he wrote, “Although we Christians are many, in the one Christ we are one. We are many and we are one — because we are united to Him.”

Vatican News reports: “In a 2023 interview with Vatican News’ Tiziana Campisi, then-Cardinal Robert Francis Prevost spoke about the significance of this motto: ‘As can be seen from my episcopal motto, unity and communion are truly part of the charism of the Order of Saint Augustine, and also of my way of acting and thinking,’ he said. ‘I believe it is very important to promote communion in the Church, and we know well that communion, participation, and mission are the three key words of the Synod. So, as an Augustinian, for me promoting unity and communion is fundamental.’[1]

Unity is also the first mark of the Church. In the Creed, we proclaim, “I believe in the one, holy, catholic and apostolic Church.” This unity of the Church flows from our belief in the one God, Father, Son and Holy Spirit. Belief in one God is the glorious heritage of Judaism: “Hear O Israel, the Lord is our God, the Lord is One” (Shema Yisrael Adonai eloheinu Adonai ehad) (Deuteronomy 6:4).[2] Jesus revealed that the one God is three Persons so totally united that he who sees the Son sees the Father.[3] This unity is brought about by the Holy Spirit, the Spirit that was poured out upon the Church at Pentecost. So we see that the unity of the Father and the Son is also the unity of the Church. Jesus prayed to His Father that His disciples might manifest this unity in their lives. “The glory that you have given me I have given them, so that they may be one, as we are one, I in them and you in me, that they may become completely one, so that the world may know that you have sent me and have loved them even as you have loved me.”[4] Commenting on this passage, St. Gregory of Nyssa writes, “That the Holy Spirit is called glory no one can deny if he thinks carefully about the Lord’s word: ‘The glory you gave to me, I have given to them.’ In fact, he gave this glory to his disciples when he said to them: ‘Receive the Holy Spirit.’ Although he had always possessed it, even before the world existed, he himself received this glory when he put on human nature. Then, when his human nature had been glorified by the Spirit, the glory of the Spirit was passed on to all his kin, beginning with his disciples.”[5]

How do we, as His disciples, manifest this unity? Since the unity of the Church is the grace of the Holy Spirit at work in the Church, we manifest that unity by cooperating with the graces that we receive from the Holy Spirit. The unity of the Church was made visible to the world on Pentecost, and in that same manifestation of unity, the multitudinous graces of the Holy Spirit were proclaimed. This is strikingly described in Luke’s account in the Acts of the Apostles: “When the day of Pentecost had come, they were all together in one place. And suddenly from heaven there came a sound like the rush of a violent wind, and it filled the entire house where they were sitting. Divided tongues, as of fire, appeared among them, and a tongue rested on each of them.”[6] Fire is one in its essence and here it is seen to be also multiple, the same fire resting individually on each of the disciples.

The effect of this united multiplicity is quickly made known: “All of them were filled with the Holy Spirit and began to speak in other languages, as the Spirit gave them ability. Now there were devout Jews from every nation under heaven living in Jerusalem. And at this sound the crowd gathered and was bewildered, because each one heard them speaking in the native language of each.”[7] Luke says both that the disciples “began to speak in other languages” and he also says that their hearers heard them each in his own language. Unity is proclaimed in multiplicity. The one Holy Spirit is manifested in multiple ways.

The Holy Spirit manifested His unity of being and of action at Pentecost as fire, and He also manifests Himself as water, for Jesus proclaimed, “Let anyone who is thirsty come to me, and let the one who believes in me drink. As [the scripture] has said, ‘Out of the believer’s heart shall flow rivers of living water.’ Now he said this about the Spirit, which believers in him were to receive.”[8]

St. Cyril of Jerusalem explains, “This is a new kind of water, a living, leaping water welling up for those who are worthy. But why did Christ call the grace of the Spirit water? Because…water comes down from heaven as rain, and although it is always the same in itself, it produces many different effects…In the same way the Holy Spirit, whose nature is always the same, simple and indivisible, apportions grace to each one as he wills…Although the Spirit never changes, the effects of his action, by the will of God and in the name of Christ, are both many and marvelous.”[9]

St. Paul says the same thing, using a striking analogy: “For just as the body is one and has many members, and all the members of the body, though many, are one body, so it is with Christ.”[10] The Holy Spirit is to the Church, the mystical body of Christ, as human DNA is to the individual human body: one’s DNA exists wholly in each cell of the body, at the same time making each cell to be uniquely what it is for the good of the whole body. The complete DNA makes a skin cell and a blood cell, a hair cell and a heart cell. In the same way, the Holy Spirit is present wholly in each believer and wholly in the whole Church.

We begin to see here the connection between unity and synodality. What is synodality? To begin with, what is it not? It is not, as some people apparently think, a democratic process for deciding what we believe. What we believe, the faith that we profess, is given by the Holy Spirit. That is the source of our unity. The faith is given. It is one because it is the knowledge of God and God is one, but the expressions of the faith are infinite because God is infinite. The Son incarnates God fully, while we each incarnate God partially as the Spirit gives us His graces. In synodal discussion, we can come to better expressions of the one faith. We can also come to a better understanding of how to live out that one faith. So we can say that synodality is the coordinated manifestation of the graces of God in the lives of all believers, graces that are received through the sacraments of the Church, through catechesis and through prayer. In other words, synodality is the life of the Trinity consciously and deliberately manifested in the members of Christ’s body.

Just as the overshadowing of the Holy Spirit brought about the incarnation of God the Son in the womb of the Virgin Mary, so too by His overshadowing in the souls and bodies of believers He incarnates the Son in the Church and thus manifests the life of God in the world. “When Christ is finally glorified, he can in turn send the Spirit from his place with the Father to those who believe in him: he communicates to them his glory, that is, the Holy Spirit who glorifies him. From that time on, this joint mission will be manifested in the children adopted by the Father in the Body of his Son: the mission of the Spirit of adoption is to unite them to Christ and make them live in him.”[11]

To return to St. Paul’s analogy of the body, “Indeed, the body does not consist of one member but of many. If the foot would say, “Because I am not a hand, I do not belong to the body,” that would not make it any less a part of the body.”[12] Each member of a person’s body is that person. If I step on your foot, I can’t say that I didn’t touch you, that I didn’t hurt you. If you hold out your hand to me and I ignore it, I am ignoring you. If I ignore a member of Christ’s body, I am ignoring Christ, just as Saul, in persecuting the members of Christ was persecuting Christ. “The eye cannot say to the hand, ‘I have no need of you,’ nor again the head to the feet, ‘I have no need of you.’”[13] Clerics cannot say to the laity, “I have no need of you”, men cannot say to women, “we have no need of you.” Neither can the pious and devout say to the lax or to sinners, “we have no need of you.” To ignore a member of Christ is to ignore Christ. Indeed, it is to ignore God, for Christ is God and as His members, we participate in His divinity.

Pope Leo understands this well, for the concept of “the whole Christ” is foundational to St. Augustine’s ecclesiology. Every baptized person is a member of Christ, and every unbaptized person is created to become a member of Christ, and the Holy Spirit is at work in each to bring this about. “All men are one man in Christ, and the unity of Christians constitutes but one man. Let us rejoice and give thanks. Not only are we to become Christians, but we are to become Christ. My brothers, do you understand the grace of God that is given us? Wonder, rejoice, for we are Christ! If He is the Head, and we are the members, then together He and we are the whole man. When by faith Christ begins to abide in the inner man, and when by prayer He takes possession of the faithful soul, He becomes the whole Christ, Head and body, and of the many He becomes one.”[14]

Synodality is living out that unity and without synodality, unity is inert and sterile.

Notes

[1] https://www.vaticannews.va/en/pope/news/2025-05/pope-leo-xiv-s-motto-and-coat-of-arms.html

[2] https://www.jewishvirtuallibrary.org/the-shema

[3] Cf. Jn 14, 9

[4] John 17, 22-23

[5] St. Gregory of Nyssa, Homily 15 Jaeger VI, 466-468, quoted in the Liturgy of the Hours, vol II, p. 958

[6] Acts 2, 1-3

[7] Acts 2, 4-6

[8] John 7, 37-39

[9] St. Cyril of Jerusalem, Catechism 16, PG 33, 931-935, Liturgy of the Hours, vol II, p 967

[10] 1 Cor. 12, 12

[11] Catechism of the Catholic Church #690

[12] 1 Cor. 12, 14-15

[13] 1 Cor. 12, 21

[14] Augustine of Hippo, In Ps. 39, enarratio 2a, P. L., Vol. 36, 219; In Ps. 127, P. L., Vol. 37, 1686; In Ps. 90, sermo 2, P. L., Vol. 37, 1159.

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