He who knows even the fundamental ideas of _Kant’s_ “Kritik der reinen Vernunft” will see that not only the Catholic Church, but every Christian denomination, might forfeit its existence if it showed itself indifferent towards it. Heresies are especially dangerous to the uneducated when they bear the names of authors of scientific repute. But the Church willingly grants the permission to read them when there is reason for it. Moreover, it was not Rome alone that took steps against _Kant_. This was done by the Prussian king _Frederick II._ also. One may recall his cabinet order, under minister _Woellner_, against Kant’s “Religion innerhalb der Grenzen der blossen Vernunft.” Similarly the works of _Spinoza_ were proceeded against, whereas his indictment by Rome now calls forth protest because he has since been assigned a prominent place among philosophers. _Freudenthal_ registers a list of 500 sharp prohibitions issued against _Spinoza’s_ works during the years 1556-1580: they were condemned by the states of Holland, by the court, by synods and magistrates. Those judgments were passed during a period when the competent authorities had views different from those of to-day; when the state deemed it its duty to oppose the undermining of Christianity. The state’s judgment has changed in many ways, Rome’s judgment has remained the same. But the works of _Kant_ and _Spinoza_ likewise have remained the same, and so is Christianity, against which they occupy an irreconcilable position, still the same. “In the moral world nothing can support that cannot also resist” is a truthful saying of _Treitschke_: it is also the principle of the Catholic Church. Without ever surrendering to the unchristian tendency of a time, she opposes error with unsubdued courage. If this be intolerance, it is not intolerance towards erring men but towards their errors, it is the intolerance that the gardener shows in uprooting harmful weeds, it is the intolerance of the physician towards disease. Obedience to the Index makes high moral demands upon the Catholic. But it has been characteristic of the Christian religion and of its faithful children never to shrink before any moral action where it appeared demanded. And if the preservation of moral purity exacts conscientious discipline, this is also true of the preservation of the pure faith, especially at a time when a neo-paganism in league with an uncontrolled mania for reading is threatening in many forms. Galileo, and Other Topics.