The letter to the Grand Duchess Christina is an essay written in 1615 by Galileo Galilei. The intention of this letter was to accommodate Copernicanism with the doctrines of the Catholic Church. Galileo tried to use the ideas of Church Fathers and Doctors to show that any condemnation of Copernicanism would be inappropriate. The letter has been described as a hallmark in the history of the relationship between science and theology, and a founding text of the Scientific Revolution.

thumb|right|Cover of Galileo's Letter to the Grand Duchess Christina, printing of 1705

Background

Christina was the daughter of Charles III of Lorraine and granddaughter of Catherine de' Medici.

thumb|left|Tiberio Titi – Portrait of Christine of Lorraine Medici, 1600

In 1611 Galileo was informed by a friend, Cigoli, that "ill-disposed men envious of your virtue and merits met [to discuss]... any means by which they could damage you." The number of scholars who disagreed with his Discourse on Floating Bodies, or were simply ill-disposed toward Galileo grew, but other than one letter from Niccolò Lorini there was not much discussion about the issue for the remainder of the year.

Late in 1613, Galileo's former student Benedetto Castelli, a Benedictine monk and lecturer in mathematics at the University of Pisa, wrote to Galileo about the events at a recent breakfast in Pisa with the Grand Duke Cosimo II de' Medici. In the course of conversation at the breakfast Cosimo Boscaglia, a professor of philosophy, argued that the motion of the Earth could not be true, being contrary to the Bible, and thus a heresy. After breakfast ended, Castelli was called back to respond to scriptural arguments against the motion of the Earth from Christina. Castelli took on the role of theologian in response, and convinced everyone there except the Duchess (who he thought was arguing mainly to hear his answers) and Boscaglia (who said nothing during this dialogue). Galileo decided to address Christina because of her desire to learn more about astronomy. Christina's position of power would also give the letter more exposure to other nobles and Church leaders.

thumb|right|Justus Sustermans – Portrait of Galileo Galilei, 1636

Galileo replied to Castelli with a long letter laying out his position on the relation between science and Scripture. By 1615, with the controversy over the Earth's motion becoming more widespread and increasingly dangerous, Galileo revised this letter and greatly expanded it; this became the Letter to the Grand Duchess Christina. The letter circulated in manuscript but was not printed until much later, after the Inquisition had condemned Galileo. It appeared in Strasbourg in 1636 with both Italian and Latin text. It was suppressed in Catholic jurisdictions, as were all works of Galileo at that period which dealt with that subject.

Contents of letter

Galileo outlined his argument as follows: To further support his argument, Galileo outlines two key premises:

  1. God has created Scripture and nature. They cannot contradict each other.
  2. Nature is independent of accommodation, but Scripture is produced to accommodate.

Galileo argues that these premises, when taken together, mean that when sensory information contradicts a long-held understanding of Scripture, a new reading must be considered in light of that information.

Doctrine of Accommodation

Galileo argues that the Bible is written in a way that is accessible to even uneducated people. Therefore, every word in the Bible cannot be taken literally. He cites an example in which God is described as having hands, which St. Augustine elucidated as not being literal. Further, Galileo cites Cardinal Baronio: "[The] intention of the Holy Spirit is to teach us how one goes to heaven and not how heaven goes."

Joshua argument

Critics of the Copernican system used the Battle of Gibeon from the tenth chapter of the Book of Joshua as scriptural evidence against heliocentrism. In the chapter, Joshua asks God to stop the Sun in order to lengthen the day and allow the Israelites to win the battle. When taken literally, this story implies that the Sun is mobile. Moreover, his letter misses out on key facts that include the Church's non-attacking stance on Copernicus when the canon proposed his heliocentric model. A Dominican theologian Tolosani made an unpublished attack on the Copernican system as early as 1544.

Furthermore, the tone of the letter was combative and overly proud. "Many resented his arrogant tone, his presumption for speaking on theological matters, and for crossing over from the world of mathematical astronomy into the world of natural philosophy."