Models of Purity: St. Thomas Aquinas’s Devotion to St. Agnes

St. Thomas Aquinas’s feast day (January 28) is the octave day of the feast of St. Agnes (January 21). While this may seem inconsequential, there are many points of connection between these two great saints.

First, they are both from central Italy: St. Agnes from Rome and St. Thomas from just south, Aquino, between Rome and Naples. Second, they both were from influential aristocratic families, Agnes from a noble Roman family and Aquinas from a mixed Germanic and Italian family, related to the Holy Roman Emperor. Third, they are both known for their exceptional purity, both having gone through terrible ordeals to test their purity in their teenage years. Finally, and most importantly, St. Thomas had an ardent devotion to St. Agnes, even keeping her relics with him at all times.

According to J.P. Torrell’s biography of St. Thomas, the saint healed his assistant, Reginald, through the intercession of St. Agnes:

[Tolomeo of Lucca] recounts a miracle performed at the castle of La Molara where they had stopped. By means of the relics of Saint Agnes that he carried with him, Thomas had cured his companion Reginald, who was in the grip of a strong fever. To celebrate the memory of this event, Thomas declared that he wanted to give his students a good dinner each year for the saint’s feast. He hardly had time to do it once, remarks the storyteller, for he died the following year (J.P. Torrell, Saint Thomas Aquinas, vol. 1, The Person and His Work, 271).

The thought of Thomas giving a feast for his students in honor of the young virgin martyr touches my heart! St. Thomas is not the remote and sterile academic that some people make him out to be! But, why would St. Thomas have such a strong devotion to St. Agnes? To answer this, let’s look briefly at her story.

Medieval image of St. Agnes.

St. Agnes, whose name in Greek means purity and in Latin lamb, died a martyr in Rome on Jan. 21st in the year 304 at the age of 12 or 13. Various accounts exist of her martyrdom, but what is common to them is that she vowed virginity (some say resisting the advances of the Roman prefect’s son), steadfastly withstood the violent pressure of the Roman prefect during her trial, was publically exposed to shame, but was miraculously preserved (some say by her hair, others by a bright light), was tortured by fire, but without harm, and was finally beheaded. She has become one of the most renowned of the early martyrs, finding a prominent place in the Roman Canon and a well celebrated feast day, becoming a central model of Christian purity.

Once again, her story bears striking connections to St. Thomas. His purity was also challenged in his adolescence, though this time by his own family (he was abducted by his brothers with the consent of his mother and even the Holy Roman Emperor). His family locked him in two of their castles for two years in an effort to persuade him to abandon the Dominican Order (his aristocratic family couldn’t stomach a son being part of a band of itinerant beggars). Getting desperate, his brothers enlisted the help of a prostitute, whom they tried to force on St. Thomas. Taking a brand from the fire, he chased her out of the room.

This part of the story is fairly well known, but there is more. Like in Agnes’s story there was a miraculous manifestation of the saint’s purity. He is said to have made the sign of the cross with the brand on the wall and to then have fallen into ecstasy. The Angelic Warfare Confraternity (more on this later) relates what happened next:

According to the records of his canonization, Thomas at once fell into a mystical sleep and had a vision. Two angels came to him from heaven and bound a cord around his waist, saying, “On God’s behalf, we gird you with the girdle of chastity, a girdle which no attack will ever destroy.” In the records of his canonization, many different witnesses who knew St. Thomas at different points in his life remarked about his evidently high degree of purity and chastity. The angels’ gift preserved St. Thomas from sexual temptation and bestowed upon him an enduring purity that ennobled all his thoughts and actions. Pope Pius XI wrote: “If St. Thomas had not been victorious when his chastity was in peril, it is very probable that the Church would never have had her Angelic Doctor.”

This point from Pope Pius XI is quite important. It is no coincidence that the Church’s greatest theologian is also known for his exceptional purity. In fact, it is precisely one of the main reasons why he could exercise such supernatural contemplation and clarity of judgment in matters of the faith. St. Thomas himself describes the importance of withdrawing from temporal distractions in order to contemplate:

For purity is necessary in order that the mind be applied to God, since the human mind is soiled by contact with inferior things, even as all things depreciate by admixture with baser things, for instance, silver by being mixed with lead. Now in order for the mind to be united to the Supreme Being it must be withdrawn from inferior things: and hence it is that without purity the mind cannot be applied to God (ST II-II, q. 81, a. 8).

Aquinas’s purity was essential to his theology, making him the Angelic Doctor, in more ways than one (another being his extensive writing on angels!).

Even with his angelic gift of purity, St. Thomas had a model of purity in his life: St. Agnes. Even the saints needed to rely on other saints. We need models of purity too! In this blessed octave, from January 21st to the 28th, we have two great models, bound together in many ways.

Oh yes, and coming back to the Angelic Warfare Confraternity! The Dominican Order sponsors this confraternity for those who want to wear a belt of chastity and dedicate themselves to purity in imitation of St. Thomas Aquinas. Please visit their website if you are interested! They also have two wonderful prayers for purity: one to St. Thomas and one written by him:

The Prayer to St. Thomas for Purity

Chosen lily of innocence, pure St. Thomas,
who kept chaste the robe of baptism
and became an angel in the flesh after being girded by two angels,
I implore you to commend me to Jesus, the Spotless Lamb,
and to Mary, the Queen of Virgins.
Gentle protector of my purity, ask them that I,
who wear the holy sign of your victory over the flesh,
may also share your purity,
and after imitating you on earth
may at last come to be crowned with you among the angels. Amen.

The Prayer of St. Thomas for Purity

Dear Jesus, I know that every perfect gift,
and especially that of chastity,
depends on the power of Your providence.
Without You a mere creature can do nothing.
Therefore, I beg You to defend by Your grace
the chastity and purity of my body and soul.
And if I have ever sensed or imagined anything
that could stain my chastity and purity,
blot it out, Supreme Lord of my powers,
that I may advance with a pure heart in Your love and service,
offering myself on the most pure altar of Your divinity
all the days of my life. Amen.

image: Radiokafka /

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R. Jared Staudt, PhD serves as Director of Content for Exodus 90. He is author of How the Eucharist Can Save Civilization (TAN, 2023) and The Beer Option: Brewing a Catholic Culture Yesterday & Today (Angelico, 2018), as well as editor of Renewing Catholic Schools (Catholic Education Press, 2020).

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