The Madonna with Horns: A False Apparition

Fr. Scott A. Haynes

A Meditation on the Discernment of Truth

Saint Peter Martyr, the False Apparition of Milan, and the Catholic Discernment of Spirits

Visitors entering the historic Portinari Chapel at the Basilica of Sant’Eustorgio in Milan encounter one of the strangest religious images of the Italian Renaissance. Painted by Vincenzo Foppa in the fifteenth century, the fresco at first appears to portray the Blessed Virgin Mary seated with the Christ Child. Yet a closer examination reveals something startling: small horns appear upon the figures. They are not some forgotten medieval symbol associated with Mary or Jesus, nor are they the result of later damage to the painting. They disclose the true identity of the apparition. The woman is not the Virgin Mary at all, but a demonic counterfeit.

The fresco depicts a medieval miracle associated with Saint Peter of Verona, better known as Saint Peter Martyr, the celebrated Dominican preacher who was assassinated in 1252. According to the medieval account of his life, a deceptive apparition appeared among heretics in Milan claiming to be the Mother of God. The apparition was convincing enough to lead people away from the Catholic faith, but Peter confronted it not with another vision or some spectacular display of supernatural power. Instead, he brought the Blessed Sacrament. Before the Eucharistic Christ, the false Madonna was exposed.

The episode is much more than a strange story from the Middle Ages. Behind Foppa’s fresco lies a rich history involving Catharism, Dominican preaching, Eucharistic faith, Saint Peter Martyr’s struggle against heresy, and the ancient Catholic tradition of discerning spirits. It also conveys an enduring warning: not every apparition comes from God, not everything supernatural is holy, and not everything containing elements of truth is therefore true as a whole. Indeed, spiritual deception is often most dangerous when falsehood is clothed in the appearance of goodness.

Milan in an Age of Religious Conflict

To understand the miracle, one must first enter the religious world of thirteenth-century northern Italy. Italy was Catholic, but it was hardly religiously tranquil. Various movements challenged ecclesiastical authority and Catholic doctrine, and among the most formidable were groups generally identified with Catharism, which had become particularly influential in parts of northern Italy and southern France.

Cathar beliefs varied according to place and period, and historians rightly caution against imagining every Cathar community as possessing an identical theological system. Nevertheless, medieval Catholic writers encountered movements characterized by a radical dualism that could regard the material world as evil or as the work of an inferior principle. Such teaching struck directly at central Christian doctrines because Christianity proclaims something astonishing about matter: God created it, God entered it, and God uses it as an instrument of grace.

“And the Word was made flesh, and dwelt among us” (John 1:14).

If Christ truly took human flesh from the Virgin Mary, then matter cannot simply be dismissed as intrinsically evil. The same truth lies beneath Catholic sacramental theology. Water becomes the instrument of regeneration in Baptism. Oil is used in sacred anointing. Human marriage is raised to sacramental dignity. Bread and wine, through the words of consecration, become the Body and Blood of Jesus Christ. The conflict with Catharism therefore concerned far more than ecclesiastical authority. It touched upon creation, the Incarnation, the sacraments, marriage, the human body, and redemption itself.

Into this troubled religious world stepped Peter of Verona.

Saint Peter of Verona

Peter was born in Verona around the beginning of the thirteenth century, traditionally about 1205. Medieval accounts emphasize that members of his family were associated with heresy, while Peter himself adhered firmly to the Catholic faith from childhood.

As a young man he went to Bologna, one of medieval Europe’s great centers of learning, where he encountered the newly founded Order of Preachers established by Saint Dominic. The Dominican vocation was particularly suited to an age of religious confusion. The friar was expected to contemplate divine truth, study it carefully, live it seriously, and then preach it persuasively. Error was not merely to be condemned; it was to be met by truth clearly understood and convincingly proclaimed.

Peter entered the Order and became one of its most celebrated preachers. His work brought him repeatedly into confrontation with heretical movements in northern Italy, while medieval accounts describe great crowds gathering to hear him. His reputation for zeal, preaching, and doctrinal clarity became formidable, and it was against this background that the extraordinary story of the false Madonna arose.

The Apparition in Milan

An early life of Peter associated with the Dominican Thomas of Lentino preserves the episode later depicted by Foppa. According to this medieval account, people came to Peter with astonishing news. An apparition claiming to be the Virgin Mary was appearing in a place associated with the Cathars in Milan.[1]

The supposed Madonna was not merely appearing silently. She was reportedly speaking against Peter and confirming the doctrines of his opponents. This gave the religious controversy a new and dangerous dimension. A theological argument could be debated, a preacher could be contradicted, and interpretations of Scripture could be examined. An apparent intervention from heaven, however, carried a different psychological force. If the Mother of God herself seemed to appear and declare that Peter was wrong, ordinary believers might naturally find themselves shaken.

According to the medieval account, the deception succeeded. A Milanese nobleman and others were persuaded by the apparition and abandoned the Catholic position.[2] This detail is particularly important because it reveals the true danger represented by the story. Those who were deceived were not necessarily trying to reject God. They apparently believed that they were following a heavenly sign.

Their error lay in accepting the sign before discerning its source. Yet this raises an important question: what exactly was the false apparition teaching, and why would its message have posed such a serious threat to the Catholic faith?

What Did the False Madonna Teach?

The medieval account leaves us with an intriguing question: what exactly did the apparition say? Thomas of Lentino does not preserve a detailed sermon or list of propositions placed upon the lips of the false Madonna. Rather, he tells us that the apparition denounced Peter and affirmed the teaching of the Cathars, persuading a Milanese nobleman and others to leave the Catholic faith.[3] We should therefore resist the temptation to supply words that the source itself does not record.

Nevertheless, the significance of the apparition would have been unmistakable. Peter was preaching against Catharism, a religious movement whose dualistic doctrines conflicted profoundly with the Catholic understanding of creation, the Incarnation, the sacraments, marriage, and the destiny of the human body. By appearing as the Blessed Virgin and apparently confirming the Cathar cause, the deception offered something far more powerful than another theological argument: it seemed to place the authority of heaven behind Peter’s opponents.

There is a profound irony in the disguise. The demon chose to appear as the very woman whose divine maternity bears witness to one of the truths most incompatible with radical dualism. Mary carried within her womb the eternal Son of God who truly assumed human flesh. She gave Him a real human body from her own body. The true Madonna therefore proclaims by her very existence that matter is not intrinsically evil and that salvation does not consist in escaping a creation that God despises.

“And the Word was made flesh, and dwelt among us” (John 1:14).

The false apparition thus employed an image of the Incarnation to lend credibility to doctrines incompatible with the Incarnation’s full meaning. Even the false Christ Child contributed to the deception, for the outward appearance seemed thoroughly Christian: Mother and Child, Mary and Jesus, heaven apparently speaking to earth. Yet the religious teaching being authenticated was false.

This is perhaps the most disturbing feature of the entire episode. The deception did not consist in denying every Christian truth, but in borrowing Christian truths and sacred images in order to make error persuasive. That is precisely why Saint Peter’s response was so powerful. Rather than arguing merely about the apparition’s appearance, he brought it before the reality to which the true Mary always points: the Eucharistic Christ.

The false Madonna could imitate Mary’s appearance, but she could not possess Mary’s faith. She could hold an imitation of the Christ Child, but she could not adore the true Christ sacramentally present before her. When Peter demanded that the supposed Mother of God acknowledge her Son, the contradiction hidden beneath the beautiful appearance was forced into the open.

The miracle therefore illustrates an essential principle of discernment: false teaching rarely needs to deny everything in order to deceive. It may preserve sacred names, familiar images, true statements, and even apparently pious exhortations while introducing an error at the point that matters most. The presence of much that is true does not transform the essential falsehood into truth.

Not Every Apparition Is from God

Here the story of Peter Martyr becomes much more than an episode in medieval hagiography. Catholic tradition has never taught that every apparition, vision, locution, dream, miracle, or extraordinary religious experience must come from God. Sacred Scripture explicitly warns Christians against such credulity.

Saint John commands:

“Dearly beloved, believe not every spirit, but try the spirits if they be of God” (1 John 4:1).

Saint Paul gives an even more unsettling warning:

“And no wonder: for Satan himself transformeth himself into an angel of light” (2 Corinthians 11:14).

These passages establish an essential principle of Christian discernment. The extraordinary character of an experience does not establish its divine origin. Something can appear beautiful without being good, produce intense religious emotion without coming from God, or speak persuasively about prayer and holiness while nevertheless introducing serious falsehood.

The devil does not ordinarily tempt by presenting evil in all its ugliness. If every temptation appeared obviously hideous, it would possess considerably less power. Deception succeeds because something attractive, desirable, or apparently good is placed before us while the disorder concealed within it remains unnoticed.

For that reason, Christian discernment must move beyond the question,

“Does this seem holy?”

The more important question is,

“Is it true?”

When Truth Is Mixed with Falsehood

One of the most important lessons suggested by the false Madonna is that deception frequently operates through a mixture of truth and falsehood. A completely absurd lie may be easy to reject, while a falsehood surrounded by many true statements can be considerably more dangerous because the truths create an atmosphere of credibility.

This method of deception appears from the opening pages of Scripture. The serpent did not begin by telling Eve simply that God did not exist. Instead, he subtly distorted what God had commanded:

“Why hath God commanded you, that you should not eat of every tree of paradise?” (Genesis 3:1).

God had not forbidden every tree. The serpent began by altering the divine command and then proceeded to direct contradiction:

“No, you shall not die the death” (Genesis 3:4).

Truth and falsehood were woven together until distrust of God entered the human heart.

The temptation of Christ reveals this strategy even more clearly because Satan quotes Scripture itself:

“If thou be the Son of God, cast thyself down, for it is written: That he hath given his angels charge over thee” (Matthew 4:6).

The biblical words were true, but their application was false. This distinction is fundamental to discernment. A quotation from Scripture does not automatically make an argument Christian, just as a reference to Mary does not make an apparition Marian and an encouragement to prayer does not by itself prove that a spiritual message comes from God. Error can survive precisely because it attaches itself to truth.

A counterfeit coin is convincing only because it resembles a real one. Spiritual counterfeits operate in much the same way.

The False Madonna Was Almost Right

Foppa’s fresco makes this principle visible with extraordinary force. The demon does not appear as a dragon or hideous monster. It appears as Mary, and the apparition does not present some immediately recognizable anti-Christian scene. Instead, it presents Mother and Child, one of the most beloved images in Christian art.

This is what makes the fresco so unsettling. The external form is almost entirely correct. A mother holds a child, the composition evokes familiar Marian imagery, and an undiscerning viewer might naturally interpret the scene as sacred. Only the horns reveal the deception.

Foppa therefore offers something more than an illustration of a medieval miracle. His fresco becomes a visual theology of temptation. Evil frequently borrows something from the good because, in the classical Christian understanding, evil possesses no fullness of its own. Saint Thomas Aquinas explains evil fundamentally as a privation, the absence of a good that ought to be present.[4] Evil therefore depends upon the good in which the defect exists.

A lie requires real words. A counterfeit must imitate something genuine. Betrayal presupposes a relationship that ought to have been faithful. Heresy ordinarily preserves certain Christian truths while distorting others. In the same way, a false apparition may borrow sacred imagery precisely because sacred imagery inspires trust.

Saint Thomas Aquinas: Goodness Requires Integrity

A principle associated especially with the moral theology of Saint Thomas Aquinas helps illuminate this problem:

Bonum ex integra causa, malum ex quocumque defectu. (“Good results from the complete integrity of the causes; evil results from any defect”).

In moral theology, the principle means that an act is morally good only when those elements necessary for its goodness are rightly ordered. A serious defect in an essential respect can render the act morally wrong.[5] Aquinas applies this principle particularly to the object, end, and circumstances of human action. A good intention cannot transform an intrinsically disordered act into a morally good one, just as doing something outwardly good for an evil purpose damages the moral quality of the action.

The same principle offers a useful analogy for spiritual discernment. Something is not proven good merely because it contains good elements. A message could contain numerous beautiful and orthodox statements while also introducing a proposition contrary to the Catholic faith. The truths do not make the falsehood true. An apparition might encourage prayer, fasting, conversion, or devotion to the Blessed Virgin while simultaneously contradicting something revealed by God. The presence of admirable elements cannot sanctify a fundamental contradiction.

Likewise, a preacher may speak eloquently about Christ while deliberately teaching something opposed to Christ, and a spiritual movement may produce enthusiasm, friendship, sacrifice, and strong religious emotion while allowing serious doctrinal error to take root. The genuinely good elements should still be recognized as good, but they cannot be used to excuse what is false.

This helps explain why spiritual deception can be so difficult to recognize. The evil may be hidden within much that is genuinely attractive.

A Necessary Qualification

The Thomistic principle should not be misunderstood to mean that a person, community, book, sermon, or report of a private revelation must be absolutely perfect in every accidental detail before anything good can be recognized within it. Human beings make mistakes, saints have sometimes displayed imperfect judgment, and witnesses may remember secondary details inaccurately. A preacher who misspeaks does not thereby become a false prophet.

The important distinction concerns what is essential to the theological or moral integrity of the matter being judged. The Church therefore distinguishes between ordinary human imperfection and genuine contradiction of the faith. When an alleged supernatural messenger teaches something contrary to what God has revealed, however, the problem is fundamental because God does not contradict Himself. Truth cannot contradict truth, and no authentic revelation from heaven can overturn the deposit of faith entrusted by Christ to His Church.

Peter Does Not Follow the Crowd

The Milanese apparition possessed another persuasive feature: people believed it. That fact might easily have intimidated a less confident preacher. Even today there is a strong temptation to assume that widespread belief itself constitutes evidence of truth, particularly when many people report intense spiritual experiences.

Christian history repeatedly warns against that assumption. Truth is not determined by numbers, enthusiasm, or social pressure. The crowd can be mistaken, while a faithful witness may stand almost alone. Peter therefore did not ask how many people had seen the apparition or how passionately they defended it. He asked whether it was from God.

That is the heart of authentic discernment.

Peter’s Answer: Bring the Apparition Before Christ

Peter celebrated Mass and, according to the medieval account, then concealed a consecrated Host within his mantle before going to the place where the apparition was appearing.[6] This is the decisive moment in the story because Peter does not attempt to defeat spectacle with a greater spectacle. He brings Christ.

Standing before the figure claiming to be the Blessed Virgin, Peter confronts her with the Eucharist. His challenge is essentially that if she truly is the Mother of God, she should adore her Son.

The logic is simple but profound. The real Virgin Mary cannot oppose Jesus Christ because her entire identity is bound to Him. At Nazareth she answers,

“Behold the handmaid of the Lord; be it done to me according to thy word” (Luke 1:38).

At Cana she directs others toward Him:

“Whatsoever he shall say to you, do ye” (John 2:5).

At Calvary she stands beside His Cross. Authentic Marian devotion therefore never replaces Christ, contradicts Christ, or draws souls away from Him. Mary leads the faithful toward her Son.

A “Mary” who contradicts Christ cannot be Mary.

The Eucharist Unmasks the Counterfeit

Peter raised the consecrated Host. According to the medieval narrative, the false Madonna was exposed as demonic and disappeared amid a tremendous noise and foul stench. The account even describes damage to the building in which the apparition had appeared.[7]

The symbolism could hardly be stronger. The counterfeit Madonna stands before the real Christ, while false supernatural power encounters sacramental reality. The apparition cannot endure the confrontation.

The Eucharistic dimension is especially significant in the context of Catharism. Catholic faith proclaims that the Son of God truly assumed human flesh and that Christ is truly present in the Eucharist. The material world is not intrinsically evil, for God Himself entered His creation and continues to use material things as instruments of grace. Peter therefore confronts a false spirituality with the sacramental Christ.

Why the False Christ Child?

There is another disturbing feature of Foppa’s fresco. The demon does not appear alone; the false Madonna holds a false Christ Child. This makes the deception still more profound because the counterfeit reproduces an entire sacred composition familiar to Christians. Mother and Child appear together, outwardly resembling countless genuine representations of the Madonna.

Yet both are false.

The theological implication is sobering. One can speak about “Jesus” and nevertheless present a false understanding of Christ. Saint Paul himself warned of those who might preach “another Jesus” (2 Corinthians 11:4). The name alone is therefore insufficient. Christianity asks who this Jesus is: true God and true man, the eternal Son who took flesh of the Virgin, founded His Church, gave His Body and Blood, commanded repentance, died upon the Cross, and rose from the dead.

Spiritual deception can preserve Christian vocabulary while quietly changing the meaning of the words. The horns in Foppa’s fresco reveal visually what theological discernment must discover intellectually.

The Martyrdom of Peter

Peter’s struggle against heresy eventually cost him his life. On April 6, 1252, while traveling from Como toward Milan, assassins attacked him near Barlassina. One of them, traditionally identified as Carino of Balsamo, struck Peter violently on the head.

According to the cherished tradition surrounding his martyrdom, Peter dipped his finger into his own blood and began writing:

Credo in Deum. (“I believe in God”).

The preacher who had spent his life defending the faith thus made his death itself a profession of faith. Peter’s martyrdom caused an extraordinary reaction, and Pope Innocent IV canonized him on March 9, 1253, less than a year after his death. His cult spread rapidly, while Sant’Eustorgio in Milan became particularly associated with his memory.

Two centuries later, that devotion would help produce one of the great monuments of Renaissance Lombardy.

The Portinari Chapel

In the fifteenth century, Pigello Portinari, associated with the powerful Medici banking interests in Milan, commissioned the magnificent chapel that bears his name at Sant’Eustorgio. The Portinari Chapel became one of the masterpieces of the early Lombard Renaissance and was intimately connected with devotion to Saint Peter Martyr.

Vincenzo Foppa was commissioned to decorate the chapel with frescoes. The surviving cycle, executed between approximately 1462 and 1468, combines Marian scenes with episodes from the life and miracles of Peter Martyr.[8] The official Museo di Sant’Eustorgio identifies among the scenes the Annunciation, the Assumption, Peter’s martyrdom, the miracle of the healed foot, the miracle of the cloud, and the miracle of the false Madonna.[9]

The horned Madonna was therefore not an eccentric image accidentally preserved in a church. She belongs to a carefully conceived artistic and theological program celebrating Catholic faith and the life of Saint Peter Martyr.

Foppa’s Brilliant Solution

Foppa faced a fascinating artistic problem. How could a painter depict a demon who had successfully pretended to be Mary? If he painted a grotesque monster, the story would cease to make sense because no one would mistake such a creature for the Blessed Virgin. Yet if he painted an entirely normal Madonna, viewers might interpret the fresco itself as an ordinary devotional representation.

His solution was ingenious. Foppa retained the recognizable form of the Madonna and Child while adding the small horns that disclose the deception. In doing so, he forces the viewer to experience, in miniature, the problem of discernment itself. At first glance the image seems sacred; only careful attention reveals that something is terribly wrong.

That is precisely the point.

Why the Church Is Cautious About Apparitions

The story also helps explain why Catholic prudence regarding alleged private revelation should never be confused with unbelief. Caution can itself be an expression of faith. If God has revealed Himself definitively in Christ, then supposed supernatural phenomena must be judged in the light of that revelation rather than revelation being judged according to the latest apparition.

Private revelation cannot become a new Gospel. An apparition cannot correct Christ, a visionary cannot overturn apostolic faith, and no apparent miracle can make a contradiction true. This remains the case even when an alleged message contains many beautiful passages, encourages prayer, or produces genuine religious enthusiasm.

Indeed, the presence of attractive elements may make careful discernment even more necessary.

The proper Catholic response is therefore neither automatic belief nor reflexive skepticism. The Church need not deny the possibility of genuine apparitions in order to investigate them carefully. She can acknowledge that God has sometimes granted extraordinary favors while also recognizing that human imagination, misunderstanding, fraud, psychological factors, and spiritual deception are possible.

The command of Saint John remains the governing principle:

“Try the spirits if they be of God” (1 John 4:1).

Why God Permits Deception

One might reasonably ask why God would permit a false apparition to deceive people who sincerely desire to follow Him. This question belongs to the larger mystery of divine permission of evil.

Saint Thomas teaches that evil does not possess an independent existence equal and opposite to good. Evil is parasitic upon good, existing as a defect or privation in something that possesses goodness.[10] God can permit created freedom and the evils arising from it without becoming the author of evil, while His providence remains capable of drawing greater goods from what He permits.

The existence of spiritual deception therefore calls Christians not to despair but to vigilance. God has not left His people without means of discernment. He has given Christ, Sacred Scripture, the apostolic faith, the sacraments, and the Church. The proper response to the possibility of false supernatural phenomena is not to abandon belief in the supernatural, but to remain firmly rooted in what God has already revealed.

The Better Question

When confronted with an extraordinary spiritual claim, Christians may naturally ask whether it could be supernatural. Peter Martyr’s story suggests that this is not yet the decisive question, because the supernatural realm includes more than divine action. The better question is whether the phenomenon leads faithfully to Christ and accords with the truth God has revealed.

A phenomenon may be extraordinary without being divine, just as something beautiful may be false and something emotionally powerful may be misleading. Popularity cannot authenticate an apparition, and the presence of some truth cannot sanctify a serious falsehood.

Saint Peter’s method is therefore remarkably sober. He does not surrender reason because something extraordinary has occurred, nor does he abandon doctrine because others are impressed. Instead, he tests the apparition against Christ and the faith.

The Lesson of the Horns

More than seven centuries separate us from Saint Peter Martyr, and more than five centuries have passed since Vincenzo Foppa painted his extraordinary fresco. Yet our own age may need its warning more urgently than ever.

We live surrounded by images and messages. Reports of visions, prophecies, dreams, predictions, healings, warnings, and private revelations can travel around the world almost instantly. A dramatic image or video can reach millions before anyone investigates its origin. Artificial images can imitate reality, stories may acquire new details as they are repeated, and religious enthusiasm can spread more quickly than careful judgment.

The greatest danger is not necessarily that people will believe something obviously evil. More often, falsehood becomes persuasive because it arrives wrapped in truth. This is how the serpent spoke in Eden, how Satan used Scripture in the temptation of Christ, and how the false Madonna in the medieval tradition reportedly deceived the faithful of Milan.

The Catholic answer is neither credulity nor cynicism. It is discernment.

“Dearly beloved, believe not every spirit, but try the spirits if they be of God” (1 John 4:1).

Before Foppa’s Fresco Today

A visitor standing in the Portinari Chapel today looks across several layers of Catholic history. There is thirteenth-century Milan, troubled by religious conflict, and there are the early Dominican friars carrying preaching and theological argument into the streets of medieval cities. There is Peter of Verona confronting heresy, the extraordinary medieval account of an apparition claiming to be Mary, and the saint raising the Eucharistic Christ before the counterfeit. There is his bloody martyrdom in 1252 and his canonization the following year. Then there is fifteenth-century Milan, wealthy and artistically sophisticated enough to produce the Portinari Chapel, where Vincenzo Foppa translated an old Dominican story into an unforgettable image.

A woman holds a child. At first they seem holy. Then the viewer notices the horns.

That small detail contains the meaning of the entire story. The difference between truth and error is not always immediately obvious. Falsehood can dress beautifully, error can speak piously, and the devil can quote Scripture. Something may contain much that is true while using those truths to carry a lie.

Saint Thomas’s principle provides an important intellectual safeguard: bonum ex integra causa, malum ex quocumque defectu. Goodness requires integrity, and a defect in something essential cannot simply be overlooked because everything surrounding it appears attractive.

Saint Peter Martyr gives the same lesson in the form of a dramatic story. The Christian must not judge solely by appearances, believe merely because something is extraordinary, or surrender the faith simply because someone claims to have received a revelation. Every spirit must be tested, and every spiritual claim must finally be measured against Christ and the truth He has revealed.

In Foppa’s unforgettable fresco, the false Madonna eventually stands before the true Christ. The disguise cannot endure. The illusion collapses, and Truth remains.

Saint Peter Martyr, pray for us.

Mary, Mother of God, pray for us.

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Footnotes

[1] Thomas of Lentino, Vita Sancti Petri Martyris, pars. 26–27, cited and summarized in Richard Stracke, “St. Peter Martyr and the False Madonna, Vincenzo Foppa,” Christian Iconography, accessed August 8, 2026, https://www.christianiconography.info/Milan/santEustorgio/peterMartyrFalseMadonna.html.

[2] Thomas of Lentino, Vita Sancti Petri Martyris, pars. 26–27. The account describes the apparition as appearing among the Cathars, denouncing Peter, confirming Cathar teaching, and persuading a Milanese nobleman and others.

[3] Thomas of Lentino, Vita Sancti Petri Martyris, pars. 26–27, cited and summarized in Richard Stracke, “St. Peter Martyr and the False Madonna, Vincenzo Foppa,” Christian Iconography, accessed August 8, 2026, https://www.christianiconography.info/Milan/santEustorgio/peterMartyrFalseMadonna.html. The account describes the apparition as appearing among the Cathars, speaking against Peter, affirming Cathar teaching, and persuading a Milanese nobleman and others to abandon the Catholic faith.

[4] Thomas Aquinas, Summa Theologiae, I, q. 48, a. 1; I, q. 49, a. 1. Aquinas treats evil not as a positive nature existing independently of good, but as a privation of a good that ought to be present.

[5] Thomas Aquinas, Summa Theologiae, I-II, q. 18, aa. 1–4. The traditional scholastic maxim bonum ex integra causa, malum ex quocumque defectu expresses the principle that the moral goodness of an act requires the integrity of those elements upon which its moral character depends.

[6] Thomas of Lentino, Vita Sancti Petri Martyris, pars. 26–27, cited in Stracke, “St. Peter Martyr and the False Madonna.”

[7] Ibid. The medieval narrative describes the false apparition disappearing amid a great noise and stench, with the walls of the building being split.

[8] Museo di Sant’Eustorgio, “The Cycle of Paintings,” Museo di Sant’Eustorgio, accessed August 8, 2026, https://www.museosanteustorgio.it/en/the-museum/cappella-portinari-eng/gli-affreschi/.

[9] Ibid. The museum dates Foppa’s cycle to 1462–1468 and identifies the Miracle of the False Madonna among the principal episodes from Saint Peter Martyr’s life depicted in the chapel.

[10] Aquinas, Summa Theologiae, I, q. 48, a. 1; I, q. 49, a. 1. Aquinas explains that evil has no direct cause precisely as evil, but arises as a defect or privation in a good subject.