Thus liberated from his persecutors, Galileo returned to Florence, where he pursued his studies with his wonted diligence and ardour. The recantation of his astronomical opinions was so formal and unreserved, that ordinary prudence, if not a sense of personal honour, should have restrained him from unnecessarily bringing them before the world. No anathema was pronounced against his scientific discoveries; no interdict was laid upon the free exercise of his genius. He was prohibited merely from teaching a doctrine which the church of Rome considered to be injurious to its faith. We might have expected, therefore, that a philosopher so conspicuous in the eyes of the world would have respected the prejudices, however base, of an institution whose decrees formed part of the law of the land, and which possessed the power of life and death within the limits of its jurisdiction. Galileo, however, thought otherwise. A sense of degradation[37] seems to have urged him to retaliate, and before six years had elapsed, he began to compose his “Cosmical System, or Dialogues on the two greatest Systems of the World, the Ptolemean and the Copernican,” the concealed object of which is to establish the opinions which he had promised to abandon. In this work the subject is discussed by three speakers, Sagredo, Salviatus, and Simplicius, a peripatetic philosopher, who defends the system of Ptolemy with much skill against the overwhelming arguments of the rival disputants. Galileo hoped to escape notice by this indirect mode of propagating the new system, and he obtained permission to publish his work, which appeared at Florence in 1632.