The Galileo Affair

The case against Galileo was two cases. In 1616, after complaints about his advocacy of the Copernican system, a panel of theological consultants judged the propositions that the sun is the centre and immobile and that the earth moves to be philosophically absurd and, respectively, formally heretical and erroneous in faith. Galileo was not tried. He was admonished by Cardinal Bellarmine to abandon the opinion, and Copernicus's book was suspended from use until corrected.

The second proceeding followed his Dialogue Concerning the Two Chief World Systems of 1632, which had passed the censors and which presented the arguments as a conversation among three speakers. The defender of the older cosmology was given the name Simplicio and, worse, arguments the pope had personally pressed on Galileo. Urban VIII, previously a supporter, took it badly. In 1633 Galileo was tried, found vehemently suspect of heresy, required to abjure, and sentenced to imprisonment commuted to house arrest, which lasted the remaining nine years of his life.

He continued to work. His Discourses on the two new sciences, arguably his most important book, was written under house arrest and printed in the Netherlands beyond the reach of the prohibition. He went blind before it appeared.

For two centuries the affair served as the standard illustration of religion suppressing science, and every element of that reading has been complicated by historians without any of them being able to make the condemnation go away.

The complications are real. The Jesuit astronomers of the Roman College were competent working scientists who had confirmed Galileo's telescopic observations and honoured him for them; their objection was that the physical proof of the earth's motion had not been supplied, which in 1616 was true. Galileo's proposed proof from the tides was wrong. The Church's formal position after 1616 permitted treating the system as a mathematical hypothesis, which was how most astronomers used it. Personal factors weigh heavily: patronage, the pope's sense of injury, and Galileo's considerable talent for making enemies. The Thirty Years War made Urban VIII politically vulnerable to charges of laxity.

None of this alters what happened. A body with coercive authority decided a question of natural philosophy by theological argument, prohibited a book, and silenced its author under threat. The complications explain how it came about and rule out the cartoon of obscurantists against a lone genius; they do not convert a condemnation into something else.

The Church revisited the case formally in the twentieth century, a commission reporting in 1992 that the theologians of the day had failed to distinguish scripture's teaching from an inherited cosmology.