The aim of the list was to protect the belief and morals of the faithful. This was done by preventing them from reading heretical and immoral books. Books thought to contain such errors included works by astronomers such as Johannes Kepler's "Epitome astronomiae Copernicanae", which was on the Index from 1621 to 1835, and by philosophers, like Immanuel Kant's "Critique of Pure Reason". The various editions of the "Index" also had the rules of the Church about the reading, selling and censorship of books. Even editions and translations of the Bible not been approved by the Church could be banned.