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The Mathematician Saint

Blessed Francesco Faa di Bruno, commemorated by the Church on March 27, is a holy friend whose vocation and holiness were at least partially inspired by Saint Don Bosco.

Saints inspire others to become saints, and the famous Saint John Bosco proves that point. Don Bosco, as everyone called him at the time, was a priest who founded religious orders of priests and sisters to serve and educate children in nineteenth century Italy.

But Don Bosco did not do that alone. His mentor, Saint Joseph Cafasso, was a priest who encouraged Bosco to begin his unconventional outreach to the abandoned children of the streets; his mother, Venerable Margaret Bosco, served as a surrogate mother for dozens of boys in Bosco’s homes; and one of Bosco’s students, Dominic Savio, was acclaimed a saint by the Church for his purity and devotion. Dominic was only fourteen years old and studying to be a priest under Bosco’s care when he died. But the saint commemorated by the Church on March 27 is yet another holy friend whose vocation and holiness were at least partially inspired by Don Bosco.

Blessed Francesco Faa di Bruno was born in 1825 in the Kingdom of Sardinia. He learned about the importance of faith in God and charity for the poor through his noble and devout parents, although his mother died when he was only nine years old.

The young Francesco decided on a military career and was a lieutenant in the army by the time he was twenty-one. Since different Italian territories fought against one another in multiple wars throughout the nineteenth century, eventually culminating in a unified Italy, military life could have been his lifelong vocation. But a battle injury and the loss of many friends in combat caused him to rethink that decision.

At first, he considered an offer to tutor the sons of a former Italian king; apparently the fact that Francesco was a devout Catholic caused that offer to be rescinded. But that disappointment only led him to pursue academic studies. While studying under two prominent scientific figures at the University of Turin and the University of Paris, he earned a doctorate in science.

Francesco began writing and publishing papers in mathematics even before he graduated and became a professor of mathematics at the University of Turin. Even today, his influence on the mathematical world is evident through the continued use of his writings and a formula involving derivatives of complex functions which is named after him. (Some argue that another mathematician was the first to state what is now popularly called the Faa di Bruno formula, but even those voices generally acknowledge that Francesco was the first to state the formula using determinants which no one else had previously discovered.)

Around the time he became a professor in Turin, Francesco became a friend of that famous resident of the city, Don Bosco. Bosco, who learned juggling and magic tricks as a boy to coax his friends to join him at Mass, had devoted his priestly life to helping the many poor, abandoned boys walking the streets of Turin. In 1859, while Bosco was founding the Society of Saint Frances de Sales to educate boys, eventually all over the world, Francesco founded the Society of Saint Zita to train domestic servants.

To modern ears this might seem like an odd thing for a mathematics professor to do, but just as Bosco’s schools helped uneducated boys learn how to live better lives and find gainful employment, so Francesco’s society helped young women develop skills that enabled them to avoid being drawn into prostitution, poverty, and unwed motherhood. The two men also worked together to form a society to protect workers from being forced to work on Sundays and to encourage Catholics in their Sunday observance.

Don Bosco became famous in his own lifetime for his educational methods, dedication to educating children, and many writings. Like Bosco, Francesco was also a bit of an overachiever. He played the organ, set up a choral school for women singers in church, and composed sacred melodies. He wrote scientific papers in both French and Italian. He developed a mechanical device to enable the blind to write (he was surely inspired to develop the device to help one of his sisters, who was going blind), as well as an electric alarm clock and a differential barometer. He founded a hospital in which the poor could recover after an illness, as well as a home for disabled and elderly women to live in. How did he raise the money for these projects? In addition to pouring his own money into these worthy causes, he convinced (begged) others to contribute.

At some point, Francesco realized that God was calling him to yet another vocation: the priesthood. He began his studies for the priesthood when he was in his forties, but the archbishop of Turin at the time frowned upon ordaining older men to the priesthood. Only when Pope Pius IX himself overruled the archbishop was Francesco allowed to be ordained in 1876 at the age of fifty-one.

One of Francesco’s brothers had been killed in battle many years before, and Francesco had his own painful memories of lost comrades from his time as a soldier. He founded the Minim Sisters of Our Lady of Suffrage to care for women and children in need (which they still do in Italy, Argentina, Colombia, and Romania), but he also taught the sisters about the importance of praying for the souls of the dead, particularly soldiers who died in battle.

One of the many reasons that the Church takes the time to honor holy men and women with the titles of “Saint” and “Blessed” is because their examples can help us address seemingly impossible problems in our own lives and times. Tempted to hide your Christian faith in a hostile work environment? Francesco’s unabashed orthodoxy lost him an important job but redirected him to a better career. Overwhelmed by the poverty and violence in our culture? Francesco could not stop civil wars, but he could find a way to provide concrete help to needy people in his own community. Comfortable with your job? Francesco did not let his pride and professional reputation keep him from hearing God’s call to leave it all behind and serve Him in a different way. Wounded by personal losses? Francesco turned his pain into prayer and led others to do the same.

Blessed Francesco Faa di Bruno died unexpectedly in 1888, the same year as his friend Saint John Bosco, proving that Heaven is a welcoming place for both mathematicians and jugglers.

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About Dawn Beutner 82 Articles
Dawn Beutner is the author of The Leaven of the Saints: Bringing Christ into a Fallen World (Ignatius Press, 2023), and Saints: Becoming an Image of Christ Every Day of the Year also from Ignatius Press. She blogs at

1 Comment

  1. Many thanks Dawn for this inspiring article. I often ask myself why I’m still Catholic (at 69) and one answer is because I read inspiring books about saints when I was a young teenager. (Vision Books were one source.) May the saints you write about protect you and promote your good work. Rick from Oregon

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