The infliction of the death-punishment for difference of opinion was still resorted to.  When Calvin caused Servetus to be burnt at Geneva, it was obvious to every one that the spirit of persecution was unimpaired.  The offense of that philosopher lay in his belief.  This was, that the genuine doctrines of Christianity had been lost even before the time of the Council of Nicea; that the Holy Ghost animates the whole system of Nature, like a soul of the world, and that, with the Christ, it will be absorbed, at the end of all things, into the substance of the Deity, from which they had emanated.  For this he was roasted to death over a slow fire.  Was there any distinction between this Protestant auto-da-fe and the Catholic one of Vanini, who was burnt at Toulouse, by the Inquisition, in 1629, for his “Dialogues concerning Nature?”

The invention of printing, the dissemination of books, had introduced a class of dangers which the persecution of the Inquisition could not reach.  In 1559, Pope Paul IV. instituted the Congregation of the Index Expurgatorius.  “Its duty is to examine books and manuscripts intended for publication, and to decide whether the people may be permitted to read them; to correct those books of which the errors are not numerous, and which contain certain useful and salutary truths, so as to bring them into harmony with the doctrines of the Church; to condemn those of which the principles are heretical and pernicious; and to grant the peculiar privilege of perusing heretical books to certain persons.  This congregation, which is sometimes held in presence of the pope, but generally in the palace of the Cardinal-president, has a more extensive jurisdiction than that of the Inquisition, as it not only takes cognizance of those books that contain doctrines contrary to the Roman Catholic faith, but of those that concern the duties of morality, the discipline of the Church, the interests of society.  Its name is derived from the alphabetical tables or indexes of heretical books and authors composed by its appointment.”

The Index Expurgatorius of prohibited books at first indicated those works which it was unlawful to read; but, on this being found insufficient, whatever was not permitted was prohibited—­an audacious attempt to prevent all knowledge, except such as suited the purposes of the Church, from reaching the people.

The two rival divisions of the Christian Church—­ Protestant and Catholic—­were thus in accord on one point:  to tolerate no science except such as they considered to be agreeable to the Scriptures.  The Catholic, being in possession of centralized power, could make its decisions respected wherever its sway was acknowledged, and enforce the monitions of the Index Expurgatorius; the Protestant, whose influence was diffused among many foci in different nations, could not act in such a direct and resolute manner.  Its mode of procedure was, by raising a theological odium against an offender, to put him under a social ban—­a course perhaps not less effectual than the other.