Galileo on Trial: A Genuine Detective Story

                                                                         Galileo Galilei (1564-1642)

Introduction

Kerk & Leven (“Church & Life”) is the leading weekly Catholic magazine in the Flemish region of Belgium. Since October 2025, on the invitation of the chief editor of the local edition of the parish of Olen, Cis Marinus, I have been writing a reflective article every two weeks from a philosophical and theological perspective, exploring Christianity in a scientific age. 

21 January 2026

Galileo on Trial: A Genuine Detective Story

In 1891, Pope Leo XIII, the predecessor of our current pope, Leo XIV, founded the Vatican Observatory, which to this day remains a leading center for scientific research. By doing so, the pope also wanted to show the world that the Church is absolutely not opposed to science. Perhaps surprising to many, the Church has always encouraged and supported astronomy, the study of the universe. When I mention this, as a philosopher of science, I am often met with raised eyebrows and the objection: “Oh really? But what about Galileo?”

Galileo Galilei (1564–1642) was an Italian mathematician, astronomer, and philosopher, and is undoubtedly regarded as the intellectual father of the modern natural sciences. Through his brilliant work, the world would change forever. Yet history would mainly remember him as the man who, in 1633, was condemned by the Roman Inquisition, the Church tribunal, because he had dared to claim that the Earth revolved around the Sun and not the other way around. This claim, the Church judged, contradicted the Bible, which recounts in the Book of Joshua how God made the sun and moon stand still, so that Joshua and his army could continue fighting the Amorites during daylight. Galileo was forced to publicly recant his position, was sentenced to lifelong house arrest, and his books were placed on the notorious Index of Forbidden Books. According to legend, he whispered “Eppur si muove” (“And yet it moves”) under his breath while signing his sentence, but this story has never been officially confirmed.

The condemnation of Galileo is often triumphantly presented as a textbook example of the incompatibility between faith and science. This is certainly the traditional way the story is told. But is this account accurate? What was the real reason Galileo was condemned? The true history reads like a genuine detective story.

Let us go back in time. Around 150 AD, the Greek astronomer Claudius Ptolemy published a model of the universe in which the Earth was a motionless sphere at the center, with all other celestial bodies (the Sun, Moon, and planets) revolving around it in perfect circles. Over the centuries, this model became increasingly complex. To keep it consistent with observed planetary motions, more and more “epicycles” had to be added, turning it into a complicated system.

In 1543, the Polish canon Nicolaus Copernicus proposed a simpler model in which the Sun was at the center and all the planets, including the Earth, revolved around it. He was careful to present his model as a purely mathematical hypothesis, not as a definitive description of reality. His work was therefore accepted by the Church and mainly discussed in academic circles. Galileo himself initially enjoyed considerable support within Church circles, especially when Cardinal Maffeo Barberini, a personal friend of Galileo, was elected pope in 1623 under the name Pope Urban VIII. Galileo was explicitly permitted to write about the Copernican system, provided he presented it as a hypothesis rather than as proven truth. In 1616, Galileo did receive an initial warning, but it was more a call for caution than a true condemnation.

In 1623, however, Galileo’s story would take an unexpected turn. That year, he published a book on a very different subject, Il Saggiatore (“The Assayer”). In this work, Galileo argued that qualities such as color, smell, and taste do not exist objectively in things themselves, but arise from the interaction between atoms and our senses. This view, an early precursor of later atomic theory, was revolutionary, but it brought Galileo into direct conflict with a central dogma of the Catholic Church: the doctrine of Transubstantiation. According to this doctrine, bread and wine in the Eucharist truly become the body and blood of Christ, while their outward properties (taste, smell, form) remain unchanged. If taste and form are merely the result of atomic interactions, the theological foundation of the Eucharist became problematic, or so it was thought at the time.

This was seen by the Jesuits in the highest circles of the Vatican as a serious threat that had to be silenced at all costs. An open condemnation of Galileo on these grounds would have triggered major theological debates and potentially undermined the authority of the Church. So they devised a clever plan: to accuse Galileo of his claim that the Earth revolves around the Sun, using it as a strategic pretext to silence him. By officially condemning him for his astronomical views, the Church could avoid a much more sensitive theological conflict.

The political context of the time played into their hands. The seventeenth century was a period of great instability: the Thirty Years' War between Catholics and Protestants was raging, the plague was devastating Italy, and the pope was under heavy pressure to demonstrate his orthodoxy. Urban VIII was accused of showing too little “apostolic zeal” and too much leniency toward Protestants. To make matters worse, in 1632 Galileo published his Dialogue, defending the Copernican model in the form of a conversation. The character Simplicio, representing the traditional view, was portrayed as not particularly intelligent. Pope Urban VIII was deeply offended, as he felt ridiculed, the simple character Simplicio was in fact a veiled reference to him.

This convergence of circumstances proved decisive. Galileo’s condemnation gave Pope Urban VIII the opportunity to restore his authority and demonstrate his “apostolic zeal.” Thanks to his friendship with Cardinal Francesco Barberini, a member of the tribunal, Galileo ultimately got off relatively lightly. After six months of house arrest in Rome, he was allowed to return to his villa in Florence, officially still under house arrest, but in very comfortable conditions.

Thus, Galileo’s condemnation was more a personal affair of “Galileo versus the Inquisition.” Nevertheless, it was not until 1992 that Pope John Paul II officially annulled the condemnation and fully rehabilitated Galileo’s name. This late rehabilitation underscores how difficult it had been for the Church to confront this turbulent episode. It remains a story that invites humility. Despite its divine mission, the Church is not an abstract, flawless institution, but a historical community of people, and therefore inevitably shares in human fallibility and vulnerability.

 

Originally published as: van Biezen, A. (2026). Galileo Galilei voor de rechter: een heus detectiveverhaal. In Kerk & Leven, edition 0485, 21 January 2026, p. 4.