During his Pontificate, Pope Leo XIV recited the Creed several times in the version preceding the addition of the Filioque. The last occasion occurred during his first apostolic-ecumenical journey to Turkey and Lebanon, and—more seriously—he also reiterated it in the Apostolic Letter In Unitate Fidei.
His perspective is clear: the unity of Christians can only be realized by returning to the so-called “foundations of the faith,” starting from what unites rather than what divides, in the conviction that the unifying element is always stronger than the differences. Unfortunately, this approach stems from the logical and theological errors that spread during the post-Vatican II crisis, particularly from irenicism, which places interreligious peace as the supreme value, and modern ecumenism, which tends to favor dialogue and compromise rather than true conversion to the Catholic faith.
Is the omission of the Filioque truly necessary to reunite the separated Churches? Or does true unity arise from a faith that is one, clear, and does not accept compromise, but only conversion and total acceptance? Let us try to understand why the Filioque is not secondary or negligible, but necessary for the profession of the one true Christian faith.
What Christians believe
Christians believe that God is one and triune. To affirm that God is Trinity is to affirm that God is Three Persons, but when we use the term “person” in reference to God, we do not use it in the same way as when we refer to human beings. Indeed, in the latter case, the different persons are instances in which the same nature—human nature—is instantiated in distinct entities through a different distribution of matter.
In the case of the divine Persons, however, they are entirely identical in substance, attributes, will, and operations, and completely devoid of matter, which helps us understand why God is one even though He is three. The Three Persons are not three gods, as Muslims misunderstand, but one God. “I and the Father,” says Jesus in the Gospel, “are one” (John 10:30), and in saying this, Christ affirmed divine unity in substance. Yet, at the same time, Jesus says, “I am not alone, but we are he and the Father who sent me” (John 8:16).
When speaking of the Trinity, one speaks of the deepest mystery, far beyond our comprehension, and therefore it is very easy to fall into errors or even outright heresies. One must not think of the three Persons as three distinct deities, as the Mormons do, nor as three parts of God or three modes of being or acting on God’s part, because otherwise one would fall into the heresy of modalism.
In the Trinity, the Father, the Son, and the Holy Spirit are distinguished only by their “relation of origin”: the Father generates the Son, and from both proceeds the Holy Spirit. This relationship is called procession.
It is not true that the Father becomes the Son at the moment of the Incarnation or becomes the Holy Spirit when dwelling in a soul (as Sabellius thought), nor that the Father causes the Son like one thing produces another, as a carpenter produces a chair (as Arius thought, and today the Jehovah’s Witnesses).
Classical Catholic theology teaches that the three Persons are precisely these three relations: we speak of three subsisting relations. And even though we speak of “relations,” God is not composed of parts, and therefore God remains simple, because everything that can be said of God coincides with His very essence. Therefore, God remains absolutely one in essence and supremely simple, while being Trinity.
How to Think About the Persons of the Trinity
To understand the Trinitarian relations well, the privileged approach is to contemplate human rationality. Indeed, Scripture says that man was made “in the image of God,” that is, in imitation of the divine nature. This divine image in us is the rational part of our soul. Therefore, by meditating on our rational nature, we can understand how the divine Persons differ while remaining identical in essence. In us, there is indeed an imprint of the Trinity. Just as by studying a footprint in the ground one can reconstruct the structure of the paw that left it, so by studying our rationality we can more precisely grasp the Trinitarian mystery.
Now, we see that, in our intellect, we perform two main operations: the first is conception, and the second is volition. When we grasp the essence of something, a concept is generated within us, yet our intellect is not altered in the least; it neither grows nor diminishes: the intellect and the concept are one. The only difference is the relation of origin.
Similarly, in God there is a procession called generation. Between the generating and the generated, however, there is no resemblance or causal relationship; they are one and the same. Yet, just as the concept is not the intellect, so the generated is not the generating. For this reason, the generated is also called Verbum, “the Word”, which precisely means concept.
Eastern schismatics apply the theological thesis of solipatrism, according to which the Son and the Holy Spirit would proceed from the single divine Person of the Father directly, thus ideally forming a triangle. Catholic doctrine, in fact, believes that the three Persons proceed from one another: the Son proceeds from the Father alone, and the Holy Spirit proceeds from the Father and the Son.
Jesus Christ is called the Son because He proceeds from the Father and is of the same divine nature. But unlike human ideas—“concepts”—which exist only in our mind, the Son exists and lives by Himself. The Father and the Son are not two separate parts: in God there are no pieces or additions. The relations that distinguish them are real and, at the same time, are the one divine substance.
The names Father and Son are the most convenient for us to refer to the divine generating and generated, since, in the sensible world, we see in father and son the closest generative relationship. They are also the most appropriate when the Son is hypostatically united with a human being, Jesus of Nazareth.
The Trinity: A Chain or a Triangle?
The human intellect also performs a second main operation, namely volition (I call it main because judgment and reasoning are two other important intellectual operations. Since they derive from and are linked to conception, they are not of our immediate concern here). Man desires what the intellect has first known to be good. Already, we can see an imprint of the Filioque in our rational nature. Just as volition proceeds from intellect and concept, so analogously the Holy Spirit proceeds from the Father and the Son.
Let us take an example. Suppose somewhere in the universe exists something we cannot conceive because we have never encountered it. No one will desire this object until they have known it, that is, until they have a concept of it and know it as good. Only after knowing an object as good can man will it. Now, volitional act and intellect are one in us: when man wills the good, his intellect neither grows nor diminishes. Only the relation of origin changes.
In the Trinity, there is therefore this second relation called spiration. To breathe (in Latin, spirare) is the vital act par excellence, and everything living is such because it desires, wants to unite with something good. The Holy Spirit is also called the Love of God, because love, in the sensitive soul, is the emotion that moves toward the good object. Similarly to the Son, the Holy Spirit—unlike volitional act in man—is subsistent, that is, exists really and by Himself, and therefore is a Person, while being consubstantial to the Father and the Son.
This explains why it is correct to conceive the Holy Spirit as proceeding from the Father and the Son. The Trinity, however, as is known, is conceived by Catholics and Eastern schismatics in two different ways according to how they conceive the relations between the Son and the Holy Spirit. The former conceive the Trinity as a chain, the latter as a triangle.
Eastern schismatics apply the theological thesis of solipatrism, according to which the Son and the Holy Spirit would proceed from the single divine Person of the Father directly, thus ideally forming a triangle. Catholic doctrine, in fact, believes that the three Persons proceed from one another: the Son proceeds from the Father alone, and the Holy Spirit proceeds from the Father and the Son.
Theological Quibbles?
Saint Thomas Aquinas responds to those who say that “divine teaching on knowledge of the Trinity is useless,” just as it would be “useless to teach man what cannot be known by human reason” (cf. Summa Theologica I, q. 31, a. 1, ad 3).
He teaches that “knowledge of the divine Persons was necessary for us for two reasons. First, so that we might have correct judgments about creation. Second, and more importantly, so that we might have correct judgments about the salvation of the human race, accomplished through the incarnate Son and through the gift of the Holy Spirit.”
“If I do not go away, the Comforter will not come to you; but if I go, I will send Him to you” (John 16:7). Jesus Himself promises to send the Spirit, reinforcing the idea that the Spirit also proceeds from the Son. And again, in another passage, the Risen Christ, appearing to the Twelve, “breathed on them and said: Receive the Holy Spirit” (John 20:22). This act of breathing is literally the act of spiration from which the word ‘Spirit’ comes.
The consequences of how one conceives the Trinity and its relations extend to the conception of man, society, economy, politics, and the Church. Regarding human nature, we have already seen the reasons. If the Trinity stands to the creature as the mold stands to the clay, then the relation of origin between volition, intellect, and conception is analogous to the relation of origin between the Holy Spirit, the Father, and the Son. Similar analogies can, in truth, also be found in the lower natural world, that is, the non-rational world, both in ourselves (everything concerning our unconscious and preconscious nature, i.e., emotional and vegetative) and in the animal and plant world, so much so that, although it is true that without Revelation one cannot know the Trinity, many ancient and pagan sages—such as Pythagoras, Plato, Aristotle—had already perceived in the number three something recurrent in the mathematical relations present in the natural world and had attributed a divine significance to it.
Regarding human salvation, accepting or rejecting the Filioque is not indifferent. If the Holy Spirit and the Son both proceed from the Father as two independent relations of origin, then—analogously—sanctification could occur without Christ. Indeed, at the ecclesiological and soteriological level, the Son stands to the Holy Spirit as Redemption to sanctification, or as the Church to the Sacraments. However, if the Holy Spirit can proceed from the Father—the origin and end of devoted life—without the mediation of the Son, then even in spiritual life, the work of sanctification could proceed and be effective without the redemption wrought by Christ and without the mediation of the Church.
This, however, is explicitly denied and condemned by Scripture, where we read, “Whoever denies the Son does not have the Father” (1 John 2:23). One cannot reach the Father if one denies the Son, but to reach the Father, one must become His child and co-heir with the Son in the Son, that is, in Christ: “And because you are sons, God sent the Spirit of His Son into our hearts, crying, ‘Abba! Father!’” (Galatians 4:6). How could the Spirit of the Father also be the Spirit of the Son if it does not proceed from the Father and the Son?
In the Gospel according to Saint John, the procession of the Holy Spirit from the Father and the Son is even clearer—both in the original Greek and in the Latin Vulgate—where it says: “When the Advocate comes, whom I will send to you from the Father, the Spirit of truth who proceeds from the Father, He will testify about me” (John 15:26). Here the Lord tells us two things: the Holy Spirit “proceeds” from the Father (ἐκπορεύεται) and the Son “sends” (πέμψω) the Holy Spirit.
Etymologically, these two words represent two distinct points: the Holy Spirit has his first origin from the Father (ἐκ-πορεύομαι = “to go out from”) and is sent by the Son, because it “passes” from Him. However, these two different points form a single subsisting relation in God, which is called the Holy Spirit, for the reasons explained above.
Elsewhere in Scripture it says: “If I do not go away, the Comforter will not come to you; but if I go, I will send Him to you” (John 16:7). Jesus Himself promises to send the Spirit, reinforcing the idea that the Spirit also proceeds from the Son. And again, in another passage, the Risen Christ, appearing to the Twelve, “breathed on them and said: Receive the Holy Spirit” (John 20:22). This act of breathing is literally the act of spiration from which the word ‘Spirit’ comes.
Therefore, the divine relation of spiration proceeds passing through the Son: it is Jesus “who breathes” and tells the apostles to receive the Holy Spirit, that is, He who has been “breathed” from Christ. The Greek verb used here is extremely rare in the Bible: ἐνεφύσησεν, literally “to blow into,” recalling the creative act of God who “breathed” into Adam to give him life (cf. Genesis 2:7).
To be continued…
