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.
Background
Christina was the daughter of Charles III of Lorraine and granddaughter of Catherine de' Medici.
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. After breakfast ended, Castelli was called back to answer 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 (whom 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.
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 argued that the Copernican theory was not just a mathematical calculating tool, but a physical reality. The letter includes a direct paragraph in which Galileo wrote: This approach caused some, including Dominican friar Niccolò Lorini, to complain to the Inquisition, which in 1616 condemned Copernicanism as philosophically absurd and contrary to scripture. Much later the Inquisition tried Galileo himself and in 1633 condemned him of suspicion of heresy.
Methodology of the letter
Galileo starts the letter with a little flattery of the Grand Duchess. He tries to build her up as an authority figure and then presents his own credentials to show that he has similar authority. Since the Grand Duchess was a person of high authority but did not have much knowledge in the field of astronomy, Galileo wrote the letter in a manner understandable to a layperson. He attempts to attain the sympathy of the Duchess by mentioning the unfair attacks made against his honor. He tried to portray “himself as a man of good will who seeks only to disclose the truth.” He states he was motivated to write the letter to justify himself to men of religion he holds in great esteem.
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.
Galileo adopts an Augustinian perspective, while also marginalizing it later. In the Letter to the Grand Duchess he references Augustine of Hippo’s work De Genesi ad Litteram, which calls for either a compromise between literal translation of scripture and astronomy or an allegorical standpoint, which could resolve future astronomical conflicts arising that could jeopardize the validity of the Bible.