Index Librorum Prohibitorum

The Index Librorum Prohibitorum, or Index of Forbidden Books, was a changing list of publications that the Catholic Church deemed heretical or contrary to morality, which Catholics were forbidden to print or read. Under Pope Paul IV a Roman Index was published in 1559, banning the entire works of some 550 authors, and from 1571 the Sacred Congregation of the Index kept it up to date. It condemned religious and secular works alike, among them Kepler's Epitome astronomiae Copernicanae and Kant's Critique of Pure Reason. The last edition, of 1948, listed 4,000 titles; in 1966 the Church declared that the Index no longer had the force of ecclesiastical law.