The Trinitarian Theology of the Eucharist according to St. Catherine of Siena

A little over fifty years ago, the Second Vatican Council declared the Eucharist “the source and summit of the Christian life.” Prior to this Council, in 1902, Pope Leo XIII described the Eucharist as “the very soul of the Church” which “brings the faithful to an intimate union with Christ through the Sacrament of His Body and Blood.” Pope John Paul II expounded on the Council’s statement in his encyclical letter Ecclesia de Eucharistia, at one point citing Vatican II’s Presbyterorum Ordinis: “the Church’s entire spiritual wealth is contained in the Eucharist because Christ himself is our Passover and living bread and this very mystery is the center of the Church’s life.” These statements, while deeply moving and true, highlight the Church’s teachings on the Eucharist from a Christological perspective.

This emphasis on the Christology of the Eucharist is not the only perspective that prevailed in the Catholic tradition. Just over a century ago, Pope Leo XIII emphasized invoking the Trinity into each of the Sacraments in his encyclical Divinum Illud Munus, when he wrote:

The Church is accustomed most fittingly to attribute to the Father those works of the Divinity in which power excels, to the Son those in which wisdom excels, and those in which love excels to the Holy Ghost [Spirit]. Not that all perfections and external operations are not common to the Divine Persons; for “the operations of the Trinity are indivisible, even as the essence of the Trinity is indivisible” (St. Aug., De Trin., I. 1, cc. 4-5); because as the three Divine Persons “are inseparable, so do they act inseparably” (St. Aug., i6.).

Centuries earlier, in the spiritual and theological writings of St. Catherine of Siena, this Trinitarian perspective is prominent. While she also embraced a Christological theology of the Body and Blood of Christ, through her “infused wisdom” and “mystic charism” she developed a profound theology of the Trinity. This paper will explore Catherine’s mystical experiences, devotion to the Body and Blood of Christ, and her theology of the Trinity, all of which brought her to this divine truth: the unity of the Trinity within the Sacrament of the Eucharist. Her journey of enlightenment empowered her to pray, write, and preach that when receiving the Eucharist, not only are the recipients sitting at that sacred dining table eating and drinking the Body and Blood of Christ, they are also being filled with grace received from each person of the Trinity — God the Father, God the Son, and God the Holy Spirit — and, in turn, share the graces received from that sacred meal with others. One should marvel at Catherine’s advanced theology, even though in the middle ages the Trinitarian relationship was not fully developed to the extent envisioned and understood by St. Catherine.

First, a summary of Catherine’s life. She was born Catherine Benincasa on March 25, 1347, in Siena, Italy, and was a twin, the 24th child of 25. She only lived to the age of 33, dying of a stroke in Rome in 1380. Catherine of Siena, often referred to as “great Kate,” is well known for her expressive life of prayer shared in three major sources of writings: over 400 letters, 26 prayers, and The Dialogue of Divine Providence, which she referred to as “the book,” written in the format of a conversation between herself and God. She was noted for her style of learning, not acquired from formal education and degrees, but gained from an interior wisdom that came from lived experiences and a mystical life of prayer. In 1461, she was canonized a saint by Pope Pius II, and in 1970, because of St. Catherine’s ecclesial role as a teacher and theologian, was declared a Doctor of the Church. While Catherine did not have any formal schooling, she attended Mass; studied the Scriptures (especially the Gospel of John); participated in Church traditions; held discussions with her confessor, Raymond of Capua, and other religious; listened to the prayers of her time; and learned through her own Dominican heritage. She attentively focused on the experience of the Last Supper and the words of institution of the Eucharist. She not only viewed all this knowledge as unified and brought their meaning alive in her own life, she spread these profound insights to others through her writings and preaching so as to bring alive the love God has for everyone and to consciously leave an imprint of the power of God within. There is no doubt the greatest influence empowering Catherine’s ministry and theology was receiving Christ himself in His Body and Blood in the Eucharist. Her understanding of the effects of receiving the Body of Christ as what feeds and sustains, while the Blood of Christ cleanses our sins, mirrored a quote found in the Summa Theologica: “the body is offered for the salvation of the body, and the blood for the salvation of the soul.”

In order to comprehend the path of Catherine’s theological development of the Trinity, it is important to follow Catherine’s spiritual journey. In Catherine’s writings, she explained the spiritual journey in three basic steps. The first step was the bridge of life as progressing in faith, which leads to the next step, a rejection of sin due to one’s love of God, which leads to ascending to the third step, true unity with the Trinity as a “filial love.” Catherine’s spiritual journey is described in more detail in Sister Mary Ann Fatula’s book, Catherine’s of Siena’s Way, as climbing up a spiritual staircase:

. . . active, one step leading to the next and building up to reach the top where a deep well of love is experienced.” For Catherine, this staircase began by embracing God’s will and living in truth taking her up the next step to an intimacy with God. It is within the “inner dwelling” of the soul where she learned to pray and discover the sacrament’s [Eucharist’s] power, and bathe in the mercy bestowed by the blood of Jesus. That mercy drew her out of self to a love that befriends brother and sister, which then embraces a radical trust in God’s providence. Continuing onto the next step leads to living the truth in love, where she found the heart of mystical union and the ultimate gift: intimacy with the triune God at which time God’s selfless love called her to pour out her life into the Church for the world’s salvation. It is when she reached the top step of the staircase where she encountered the Triune God’s intimate presence and power that transformed not just the way she prayed, but also how she lived.

This upward movement is seen in Catherine’s own spiritual journey, as she ultimately ascended to the top of this staircase using her mystic charism to explain the dynamics and mystery of the Trinity. This is witnessed in Catherine’s spiritual life from the very beginning within the depths of intimate silence inside the solitary simpleness of the cell in her heart to her brazen preaching to the Roman Curia. She emerged from a three-year period of reclusiveness to minister to people, ranging from the poorest of the poor to prostitutes to prisoners to the Pope seated in the highest place of power. She began her journey in simple silent prayer and, as she continued on, Catherine preached, she wrote, she prayed, and she contemplated many great mysteries in this life. She reached the top of the spiritual ladder in her contemplation and development of the mystery of the Holy Trinity, and all the components [prayers, teaching, experience] of her life flow in and out of each other, “in union with the joyful interplay of the Creator, the Son, and the Spirit.”

Catherine explicitly understood the Trinity as “relationship.” She expressed her Trinitarian thoughts using symbolic and unified language as she wrote countless parallels, symbols, and expressions to better understand the dynamics of that very relationship within the three persons in the Trinity. This is especially evident in Catherine’s twenty-six prayers that have been preserved and transcribed by people who witnessed Catherine praying aloud. The majority of her prayers centered on addressing, or are intercessory prayers to one or both or all of, the three persons of the Trinity. Even when Catherine would pray to one person in the Trinity, she united them. For example, in Prayer 3, she referenced God as the “way, truth, and life,” but the “identity Catherine seems to draw here between the Father and Jesus is consistent with her statements elsewhere that where one person of the Trinity is, the whole Trinity is active.”

Catherine’s creative imagery and language in her prayers personalize and build upon that very Trinitarian spirituality and the close relationship between each person in the Trinity. She would often describe the Trinity using imagery and themes reflecting human attributes; for example, the acts of remembering, understanding and desiring; memory; understanding and will; power, wisdom and tender clemency [mercy]; O eternal Truth, O eternal Fire, O Eternal Wisdom or Life, Wisdom and Light. She would also describe the Trinity with themes related to nature, e.g., peaceful sea, one vine with three branches (Jn 15:5), Tree of Life, or eternal garden.

In addition to Trinity and Godhead, Catherine would use one word to address all three persons together: Charity, Compassion, Truth, Wisdom, Light, Doctor, Fire, Strength, Splendor and Life. And in Prayers 1, 11, and 13, she specifically referenced the faithful as being created in the Trinity’s image, “fashioned [us] after the very Trinity.” In these prayers, Catherine fully understood the presence of the Trinity in the creation story from the very beginning in the book of Genesis. She united all people into the relationship within the three persons in the Trinity.

Catherine then took the Trinity even deeper into the human experience of relationship. It is apparent in Catherine’s writings that while attending Mass, she would listen attentively to the Eucharistic prayers from the Roman Canon. In Dialogue 111, she wrote about how the soul comprehends the Eucharist from the lens of the Trinity being close and present while also being united with the humanity and divinity of Christ:

What tastes and sees and touches this sacrament? The soul’s sensitivity. How does she see it? With her mind’s eye, so long as it has the pupil of holy faith. This eye sees in that whiteness [the host] the divine nature joined with the human; wholly God, wholly human; the body, soul, and blood of Christ, his soul united with this body and his body and soul united with my divine nature, never straying from me.

Catherine described later in Dialogue 111 the presence of the three persons of the Trinity, as she transcribed in one of her ecstasies what God observed about her response during the Eucharistic prayer:

When the celebrant reached the consecration, you looked up toward him. And at the words of consecration I revealed myself to you. You saw a ray of light coming from my breast, like the ray that comes forth from the sun’s circle yet never leaves it. Within this light came a dove, and dove and light were as one and hovered over the host by the power of the words of consecration the celebrant was saying. Your bodily eyes could not endure the light, and only your spiritual vision remained, but there you saw and tasted the depths of the Trinity, wholly God, wholly human, hidden and veiled under that whiteness. Neither the light nor the presence of the Word, whom in spirit you saw in this whiteness, took away the whiteness of the bread. Nor did the one stand in the way of the other. I did not block your sight either of me, God and human, in that bread, or of the bread itself. Neither the whiteness nor the feel nor the taste was taken away from the bread.

Catherine often experienced ecstasies which she described as being united with God through affection of love. She would lose her bodily powers, almost falling into a deep sleep, her memory being filled with God. Catherine described a moment in ecstasy with the Trinity before writing a prayer, repeating her conversation with God: “I let my body lie just as it was, and kept my understanding fixed on the abyss of the Trinity.”

It was in Catherine’s actually receiving Holy Communion where she experienced divine enlightenment. Most especially she “ascended to the Trinity, there to contemplate the ‘Three Faces in one single Substance.’” She referred to the Eucharist as the “Sweet Sacrament,” and when one received the Eucharist in the light of faith, “you will see in the Host the whole God and the whole man.” She understood how Jesus gave Himself completely to us, and that indeed he gave His divinity and humanity, with His whole being as God and man, and that, in the sending of the Holy Spirit over the gifts, also filled the people with the same Holy Spirit. Thus, she believed the bread and wine became the Body and Blood of the glorified Christ as spiritual nourishment, thereby becoming “Spirit-ized” — filled with the Holy Spirit — and those who partake of the Body and Blood of Christ by making the glorified Lord present in them. She was spiritually transformed until she became what Paul writes in his letter to the Galatians 2:20: “It is now no longer I that live, but Christ that lives in me.” As she wrote in Dialogue 128, “I truly believe that you are Christ, the Son of the true and living God, given to me as food by the fire of your immeasurable charity and in memory of your most tender passion and the great blessing of your blood poured out with such burning love to wash away our sinfulness.”

Catherine used adjectives relating to what the body craves when it needs sustenance in some of her writings, describing Jesus’s Blood as being pure grace. She also spoke of the need in everyone to thirst for the Blood of Jesus in order to quench one’s thirst for pure grace. Catherine found in Jesus’s Blood “the love of God made human, the mercy of God made visible.” Catherine ties the Trinity to the Blood of Christ in the Eucharist and uses language relating to being hungry:

Eternal God, Eternal Trinity, You have made the Blood of Christ so precious through His sharing in your Divine Nature. You are a mystery as deep as the sea; the more I search, the more I find, and the more I find the more I search for You. But I can never be satisfied; what I receive will ever leave me desiring more. When You fill my soul I have an ever-greater hunger, and I grow more famished for Your Light. I desire above all to see You, the true Light, as you really are.

The depth and outpouring of her insights into the Blood of Christ brought her directly into “mystical union” with God, not only “creating an intimate bond with God,” but with God’s people.

Catherine used her extraordinary gift of expressive language in developing her theological dynamics of the Trinity as she often related the human function of dining or the need to eat to satisfy hunger and thirst to explain the presence of the Trinity at the Eucharistic table. In Dialogue 112, Catherine relays God’s response:

Dearest daughter, contemplate the marvelous state of the soul who receives this bread of life, this food of angels, as she ought. When she receives this sacrament she lives in me and I in her. Just as the fish is in the sea and the sea in the fish, so am I in the soul and the soul in me, the sea of peace. Grace lives in such a soul because, having received this bread of life in grace, she lives in grace. When this appearance of bread has been consumed, I leave behind the imprint of my grace, just as a seal that is pressed into warm wax leaves its imprint when it is lifted off. Thus does the power of this sacrament remain there in the soul; that is, the warmth of my divine charity, the mercy of the Holy Spirit, remains there. The light of my only-begotten Son’s wisdom remains there, enlightening the mind’s eye.

And later in the Dialogue, Catherine links the Trinity to the only food that could satisfy the hunger in her soul:

O eternal Trinity. O Godhead! That Godhead, your divine nature, gave the price of your Son’s blood its value. You, eternal Trinity, are a deep sea: The more I enter you, the more I discover, and the more I discover, the more I seek you. You are insatiable, you in whose depth the soul is sated yet remains always hungry for you thirsty for you, eternal Trinity, longing to see you with the light in your light.


In one letter she wrote, “Who does not know is not able to love and one who knows, so loves.” This notion tells us how key the role love plays in one’s ability to understand one’s love and hunger for the Eucharist. Catherine described her dining at the Eucharistic table as a spiritual experience in Dialogue 111:

How is this sacrament tasted? With holy desire. The body tastes only the flavor of bread, but the soul tastes me, God and human. So you see, the body’s senses can be deceived, but not the soul’s. In fact, they confirm and clarify the matter for her, for what the mind’s eye has seen and known through the pupil of holy faith, she touches with the hand of love. What she has seen she touches in love and faith. And she tastes it with her spiritual sense of holy desire, that is, she tastes the burning, unspeakable charity with which I have made her worthy to receive the tremendous mystery of this sacrament and its grace. So you see, you must receive this sacrament not only with your bodily senses but with your spiritual sensitivity, by disposing your soul to see and receive and taste this sacrament with affectionate love.

Catherine’s theological development of the Trinity in the Eucharist becomes even more evident when she has a profound mystical experience. During the lifetime of Catherine, Holy Communion was rarely received. In 1215, the Fourth Lateran Council decreed it was only a requirement to receive Communion at least once per year for two reasons. The first reason people abstained was an emphasis on the Augustinian view of original sin that people were unworthy and too sinful to partake of the Eucharist. Secondly, “ocular” communion was just as valid as physical consumption, in that if one laid eyes on the host, it was the same as receiving the host. But Catherine had an insatiable desire to receive Communion as often as she possibly could. Even her confessor, Raymond of Capua, spoke of how Catherine was scandalized because of her frequent need to receive Communion. On one occasion when the Mass had ended and Catherine had not received Communion, she claimed she must not be worthy enough and later had an ecstasy which she described in Dialogue 142. God spoke to Catherine saying:

Then I who exalt the humble drew to myself this soul’s love and longing and gave her knowledge in the abyss of the Trinity, myself, God eternal. I enlightened her understanding in my own the Father’s power, in the wisdom of my only-begotten Son, and in the mercy of the Holy Spirit — for we are one and the same thing.

In another ecstasy, God explained to Catherine the intensity of the Trinity’s union within the Eucharist:

I have said that this body of his is a sun. Therefore you could not be given the body without being given the blood as well; nor either the body or the blood without the soul of this Word; nor the soul or body without the divinity of me, God eternal. For the one cannot be separated from the other — just as the divine nature can nevermore be separated from the human nature, not by death or by any other things past or present or future.

It is in Prayer 12 where Catherine employs Trinitarian language for the Eucharistic feast. She eloquently described the relationship of the Trinity in the Eucharist as “table,” “food,” and “waiter” for us. God the Father is the table which offers us the food, and Jesus, the Lamb, God’s son is the food, both in his teaching and in the Eucharist and that which feeds and strengthens us as we travel through this life. The Holy Spirit is the “waiter” who “serves us the food and enlightens and inspires us and what is really hungry — that part of us that desires God is our soul.” This image of table, food, and waiter is an image all people can relate to. All who hunger for God are welcome to dine at this Eucharistic feast. This very prayer summarizes Catherine’s Eucharistic Trinitarian theology as it expresses the ultimate invitation to dine at the Eucharistic meal and receive everything needed to get through this journey of life. (See Prayer 12 at the conclusion of this essay).

Time and again, Catherine unites the Triune God as part of the Eucharistic experience and as a reciprocal relationship of grace and love. She clearly understood the Eucharist as the source that gives us the spiritual energy that drives our lives and, in turn, empowers us to minister to others. Catherine’s theology of the Triune nature of the Eucharist received through the Body and Blood of Christ supports the continuous movement and outpouring of grace that satisfies hunger, heals, unites, and spreads God’s love into others.

Six hundred years after Catherine, Pope St. John Paul II wrote, in Dominum et Vivificantem (“On the Holy Spirit in the Life of the Church and the World”), reflections on the Trinity and the Eucharist that bear and echo Catherine’s unique mystical voice:

The Holy Spirit as Love and Gift comes down, in a certain sense, into the very heart of the sacrifice which is offered on the Cross. Referring here to the biblical tradition, we can say: He consumes this sacrifice with the fire of the love which unites the Son with the Father in the Trinitarian communion. . . . This truth about the Holy Spirit finds daily expression in the Roman liturgy, when before Communion the priest pronounces those significant words; Lord Jesus Christ, Son of the living God, by the will of the Father and the work of the Holy Spirit your death brought life to the world . . .

Pope St. John Paul II also wrote “the Holy Eucharist is what fuels us and gives us hope in our work and increases our sense of responsibility to the world today.” We, in essence, become Eucharistic by our commitment to transforming the world in accordance with the Gospel. This statement also supports Catherine’s thoughts about the Eucharist as a transformative experience when she described the people being candles and by themselves, remain unlit, but after receiving the Sacrament of the Eucharist, become lit. She embraced that same interior knowledge that when one is nourished by Christ in the Eucharist, and then reaches out to help one’s neighbor with the love and grace received in the Eucharist, these acts of love flow out from the Trinity.


Centuries later, one can study Catherine’s spiritual journey, her devotion to the Body and Blood of Christ, and her remarkable understanding of the Trinity, and we can contemplate her wisdom of the Trinity so alive in the Eucharist. “Here, in the depths of the trinitarian life, Catherine discovered the abyss of love infinite enough to satisfy our thirst and to reveal our own deepest meaning: in Jesus the triune God and humanity have become one.” Her life narrative is so relevant to Catholics today, not just because Catherine is an important part of the heritage of the Church, but also by her passion in our own potential to know the Holy Trinity personally, pastorally, and prophetically. Catherine’s deep love of the Triune God manifests itself by her own imperative to live out loving the Holy Trinity by being fully involved in loving others. Her words, prayers, and images, most especially Catherine’s depiction of dining with the Godhead in the Eucharist when she describes them as “table, food, and waiter,” offers a concise, yet intimate relational oneness in the Trinity, which takes us to the highest step on the spiritual staircase — as being food for our souls for the salvation of the world. There is no doubt that if St. Catherine of Siena were alive today, she would completely agree that the Eucharist truly is “the source and summit of the Christian life.”

St. Catherine of Siena, Prayer 12, V 124–157

And by the light of most holy faith
I shall contemplate myself in you.
And I shall clothe myself in your eternal will,
And by this light I shall come to know
That you, eternal Trinity,
Are table
And food
And waiter for us.
You, eternal Father,
Are the table
That offers us as food
The Lamb, your only-begotten Son.
He is the most exquisite of foods for us,
Both in his teaching,
Which nourishes us in your will,
And in the sacrament
That we receive in Holy Communion,
Which feeds and strengthens us
While we are pilgrim travelers in this life.
And the Holy Spirit
Is indeed a waiter for us,
For he serves us this teaching
By enlightening our mind’s eye with it
And inspiring us to follow it.
And he serves us charity for our neighbors
And hunger to have as food
And the salvation of the whole world
For the Father’s honor
So we see that souls enlightened in you,
True light,
Never let a moment pass
Without eating this exquisite food
For your honor.


Select Works Cited and Consulted

Baldwin, Anne B. Catherine of Siena: A Biography. Huntington: Our Sunday Visitor, 1987.

Bokenkotter, Thomas. A Concise History of the Catholic Church. New York: Doubleday, 2004.

Catherine of Siena. The Dialogue, 2nd ed. Translated and edited by Suzanne Noffke, OP. Mahwah, NJ: Paulist Press, 2001.

Catherine of Siena. The Prayers of Catherine of Siena, 2nd ed. Translated and edited by Suzanne Noffke, OP. Lincoln, NE: Authors Choice Press, 2001.

Catherine of Siena. The Letters of St. Catherine of Siena, 2nd ed. Translated by Suzanne Noffke. Lincoln, NE: Authors Choice Press, 2001.

Catherine of Siena. The Letters of St. Catherine of Siena. Translated by Vida D. Scudder (1905). Edited by Darrell Wright. 2016.

Fatula, OP, Mary Ann. Catherine of Siena’s Way, vol. 4. Wilmington, DE: Michael Glazier, 1987.

Giallanza, CSC, Joel. Source and Summit: Six Great Spiritual Guides Talk About the Eucharist. St. Paul’s: Alba House, 2005.

Hahn, Scott. The Lamb’s Supper: The Mass as Heaven on Earth. New York: Doubleday, 1999.

Hilkert, Mary Catherine. Speaking With Authority: Catherine of Siena and the Voices of Women Today. New York: Paulist Press, 2001.

Jeremiah, Mary. The Secret of the Heart: A Theological Study of Catherine of Siena’s Teaching On the Heart of Jesus. Front Royal: Christendom Press, 1995.

Pope Paul VI. “St. Catherine, Doctor of the Church.” L’Osservatore Romano, 42, 133. October 15, 1970.

Kunzler, Michael. The Church’s Liturgy. London: Continuum, 2001.

Meade, CSJ, Catherine M. St. Catherine of Siena: My Nature Is Fire. Staten Island, NY: Alba House, 1991.

McAfee, Shaun. “5 Things You Didn’t Know About Communion in the Middle Ages.” April 27, 2015.

McKenna, CM, John H. The Eucharistic Epiclesis: A Detailed History from the Patristic to the Modern Era. 2nd ed. Mundelein, Illinois: 2009.

Murray, OP, Fr. Paul. Study guide to Bishop Robert Barron’s Catholicism: The Pivotal Players, Volume I, 1–30. Word on Fire Catholic Ministries: 2016.

Noffke, OP, Suzanne. Catherine of Siena: Vision Through A Distant Eye. Collegeville: The Liturgical Press, 1996.

O’Carroll, Michael. Corpus Christi: An Encyclopedia of the Eucharist. Wilmington: Michael Glazier, 1988.

O’Driscoll, Mary, ed. Catherine of Siena: Passion for the Truth, Compassion for Humanity. Hyde Park, NY: New City Press, 1993/2005.

Raymond of Capua. The Life of Catherine of Siena. Trans. Conleth Kearns. Wilmington: Michael Glazier, 1980.

Vinje, Patricia Mary. Praying with St. Catherine of Siena; Companions for the Journey. Winona, Minnesota: St. Mary’s Press, 1990.

Wiseman, Fr. Vincent. “I Am Hungry: Catherine of Siena and The Eucharist.” Dominican Torch 3 (Spring, 2005): 32–33.

Mary George-Whittle About Mary George-Whittle

Mary George-Whittle is a board-certified chaplain with the National Association of Catholic Chaplains and served as the Director of Spiritual Care at Mary's Woods at Marylhurst in Lake Oswego, Oregon, and Mohun Health Care Center in Columbus, Ohio. She and her husband, Bill, are retired and currently attend St. Patrick's Catholic Community in Scottsdale, Arizona. Mary is deeply grateful for the guidance and advice given while writing this paper by Dr. Leo Madden at Ohio Dominican University.


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