It was in vain to meet such arguments by any other weapons than those of the civil power. His enemies saw that they must either crush the dangerous innovation, or allow it the fullest scope; and they determined upon an appeal to the inquisition. Lorini, a monk of the Dominican order, had already denounced to this body Galileo's letter to Castelli; and Caccini, bribed by the mastership of the convent of St. Mary of Minerva, was invited to settle at Rome for the purpose of embodying the evidence against Galileo.
Though these plans had been carried on in secret, yet Galileo's suspicions were excited; and he obtained leave from Cosmo to go to Rome about the end of 1615.[22] Here he was lodged in the palace of the grand duke's ambassador, and kept up a constant correspondence with the family of his patron at Florence; but, in the midst of this external splendour, he was summoned before the inquisition to answer for the heretical doctrines which he had published. He was charged with maintaining the motion of the earth, and the stability of the sun, with teaching this doctrine to his pupils, with corresponding on the subject with several German mathematicians, and with having published it, and attempted to reconcile it to Scripture, in his letters to Mark Velser in 1612. The inquisition assembled to consider these charges on the 25th of February, 1615; and it was decreed that Galileo should be enjoined by cardinal Bellarmine to renounce the obnoxious doctrines, and to pledge himself that he would neither teach, defend, nor publish them in future. In the event of his refusing to acquiesce in this sentence, it was decreed that he should be thrown into prison. Galileo did not hesitate to yield to this injunction. On the day following, the 26th of February, he appeared before cardinal Bellarmine, to renounce his heretical opinions; and, having declared that he abandoned the doctrine of the earth's motion, and would neither defend nor teach it, in his conversation or in his writings, he was dismissed the court.
Having thus disposed of Galileo, the inquisition conceived the design of condemning the whole system of Copernicus as heretical. Galileo, with more hardihood than prudence, remained at Rome for the purpose of giving his assistance in frustrating this plan; but there is reason to think that he injured by his presence the very cause which he meant to support. The inquisition had determined to put down the new opinions; and they now inserted among the prohibited books Galileo's letters to Castelli and the grand duchess, Kepler's epitome of the Copernican theory, and Copernicus's own work on the revolutions of the heavenly bodies.