Tommaso Caccini

In Florence, Caccini became a member of a group known as the "Pigeon League", named after Lodovico delle Colombe.[3]

Colombe was reputed to be one of the first individuals in the Church to attempt to derail Galileo Galilei's scientific endeavors. Another famous member of the Pigeon League was Niccolò Lorini, who often utilized references to Scripture in his fiercely critical sermons against Galileo.[4]

Colombe denounced Galileo's discussion of Copernican theory, soon after Galileo confirmed several celestial discoveries in 1609. Lorini followed by issuing a scathing sermon in 1613 responding to Galileo's Letters on Solar Spots.[1][5] Soon after Lorini's sermon, Galileo issued a response, known as the Letter to Benedetto Castelli. The Letter attempted to demonstrate that Copernican theory and the Book of Joshua were not mutually exclusive.[1] Caccini saw the Letter to Castelli as an opportunity to discredit Galileo and his followers even further.

On December 20, 1614, Caccini issued a sermon at the Santa Maria Novella in Florence strongly opposing Galileo's support of Copernican theory.[1] While the exact text of the sermon is not clear, historians suggest that Caccini preached that mathematics and science were contrary to the word of the Bible, and therefore, heretical.[6] Although Caccini appeared to have criticized mathematics and science generally, he singled out Galileo and his followers. He made a point to utilize the biblical phrase, "Ye Men of Galilee, why stand you gazing up in heaven?"[7] (in the Latin version found in the Vulgate: Viri Galilaei, quid statis aspicientes in caelum?). The phrase can be found in Acts 1:11. The phrase refers to the inhabitants of Galilee who gazed into the sky expecting Jesus to return as he made his way to heaven.[7] Caccini attempted to play on the words of the passage by starkly contrasting Galileo's allegedly heretical acts to the unwavering faith of the inhabitants of Galilee.[7]

Despite opposition from relatively high-ranking members in the Dominican order towards Caccini's views, some historians speculate that Caccini's sermon was the catalyst for the trial of Galileo that took place in Rome in 1615.[9] By the time the Holy Office called Caccini to testify against Galileo, he was residing at the Roman convent of Santa Maria sopra Minerva. Caccini was an alumnus of the College of St. Thomas, the future Pontifical University of St. Thomas Aquinas, Angelicum having become Master and Bachelor there.[10] On March 20, 1615, in front of several high-ranking officials within the Church, Caccini testified regarding his sermon and his knowledge of Galileo and his followers. Caccini stated that following his sermon, he reported to the Father Inquisitor in Florence that Galileo's supporters should be disciplined for their "petulant minds."[11] Caccini accused Galileo's followers of making blasphemous statements that questioned God's existence and the Church's declaration that miracles were acts performed by saints.[12] Caccini went on to state that the notion that the earth travels around the sun was offensive to the Scripture, which declared the earth motionless.[13]

In addition to discussing his activities following the sermon, examiners asked Caccini to discuss his opinions regarding Galileo and his followers. Despite the fact that Caccini clearly despised Galileo's teachings, he attempted to act diplomatically when asked about Galileo's character. He openly noted that Galileo had been regarded as "a good Catholic" by many.[14] Nonetheless, Caccini demonstrated his disapproval of Galileo's views subtly in his closing statement. When asked if he had any hostility towards Galileo or his followers, Caccini responded "...I do not have any hostility towards Galileo...or toward [the] disciples of Galileo. Rather I pray to God for them."[15]

While Caccini hoped that his claims would encourage Rome to act against Galileo, his testimony was met with mixed reviews. Most of his claims were disregarded by the Church with the exception of the claim that Galileo's Letter on Sunspots was heretical.[1] In 1616, following an examination of the Letter, the Holy Office issued a report that the notion of a stationary sun was heretical.[1] The Holy Office further enjoined Galileo on February 26, 1616 from teaching or defending the notion that the earth revolved around a stationary sun.[16]

After giving his testimony in 1615, Caccini used his opposition to Galileo as a vehicle to achieve his ambitious professional goals. Gradually his career progressed in Rome, and he eventually became the prior of the monastery of San Marco where he continued to assist in the prosecution of Galileo. Caccini died at the age of 74 in Florence in 1648.[1]

• Galileo Galilei