Two years after this appeal to the new Protestantism to make the great venture of spreading its truth by love and persuasion, there came from Geneva the decisive answer in the burning of Servetus, followed by the famous _Defence_ before the world, written mainly by Calvin, of the course that had been taken. One month later, a brief Latin work appeared from the press with the title, _De haereticis, an sint persequendi, etc._ (Magdeburgi, 1554), followed in very short time by a French edition (Rouen, 1554). The body of the work contained impressive passages in favour of toleration from Church Fathers, from Luther, Erasmus, Sebastian Franck, and others, concluding with a passage from "Basil Montfort," a name which thinly veils Bastian Castellio himself. The Preface was addressed to the Duke of Wurtemberg, bore the name of "Martinus Bellius," and was beyond doubt written by Castellio, who inspired and directed the entire work, in which he was assisted by a very small group of refugees in Basle of similar ideas on this subject to his {94} own. This Preface is one of the mother documents on freedom of conscience, from which in time came a large offspring, and it is, furthermore, an interesting interpretation of a type of Christianity then somewhat new in the world. Its simplicity, its human appeal, its restrained emotional power, its prophetic tone, its sincerity and depth of earnestness mark it as a distinct work of genius, almost in the class with Pascal's _Provincial Letters_.