The Congregation of the Index and the Copernican Decree

Meanwhile, Inquisition proceedings continued. On February 24th, 1616, eleven consultants met in the Vatican to consider two propositions taken from Caccini’s deposition: that the Sun is the center of the world; and that the Earth is not at the center of the world, nor motionless. Both propositions, these theologians agreed, were foolish and absurd according to science. Moreover, they concluded, according to the Faith the first is heretical and the second is at least erroneous. However, Cardinal Orsini, Cardinal Caetani, Cardinal Bellarmine and others did not wish to create a public spectacle at the expense of the Grand Duke’s mathematician. Cardinal Maffeo Barbarini defended Galileo’s Letter to the Grand Duchess Christina before Pope Paul V, and as a result the decree issued by the Congregation of the Index stopped short of censuring Galileo or prohibiting any of his works. Nor did it declare Copernicanism “heretical” or “erroneous in the Faith.” But the De revolutionibus of Copernicus would be added to the Index of Prohibited Books until it could be corrected.

Four years later, in 1620, the Congregation of the Index published a total of ten corrections to Copernicus, making it permissable for Catholics, including Galileo, to read and discuss it again. The correction on this page (Figure 1) is typical: where Copernicus wrote of "the demonstration of the triple motion of the earth," the handwritten correction amends it to "the demonstration of the hypothesis of the triple motion of the Earth." Similar corrections are made in the other nine places throughout the book, to ensure that a mathematical discipline would be interpreted hypothetically. (Figure 2)

The Index decree of 1616 suspended Copernicus until corrected, and prohibited the Letter of Foscarini. Text of the decree of the Index, and other relevant documents, are translated in Finnochiaro, The Galileo Affair.

Exhibit credit: Kerry Magruder, with the assistance of , Marilyn B. Ogilvie, Duane H. D. Roller.