use of other arguments, they already make the transition into the systems of the first kind, and may degenerate into a mixture of the two, which brings more danger than advantage, for their invaluable prerogative of being imparted to _children_ gives them the surest guarantee of the permanent possession of the mind, for thereby their dogmas grow into a kind of second inborn intellect, like the twig upon the grafted tree; while, on the other hand, the systems of the first kind only appeal to grown-up people, and in them always find a system of the second kind already in possession of their convictions. Both kinds of metaphysics, whose difference may be briefly expressed by the words reasoned conviction and faith, have this in common, that every one of their particular systems stands in a hostile relation to all the others of its kind. Between those of the first kind war is waged only with word and pen; between those of the second with fire and sword as well. Several of the latter owe their propagation in part to this last kind of polemic, and all have by degrees divided the earth between them, and indeed with such decided authority that the peoples of the earth are distinguished and separated more according to them than according to nationality or government. They alone _reign_, each in its own province. The systems of the first kind, on the contrary, are at the most _tolerated_, and even this only because, on account of the small number of their adherents, they are for the most part not considered worth the trouble of combating with fire and sword—although, where it seemed necessary, these also have been employed against them with effect; besides, they occur only in a sporadic form. Yet in general they have only been endured in a tamed and subjugated condition, for the system of the second kind which prevailed in the country ordered them to conform their teaching more or less closely to its own. Sometimes it not only subjugated them, but even employed their services and used them as a support, which is however a dangerous experiment. For these systems of the first kind, since they are deprived of power, believe they may advance themselves by craft, and never entirely lay aside a secret ill-will which at times comes unexpectedly into prominence and inflicts injuries which are hard to heal. For they are further made the more dangerous by the fact that all the real sciences, not even excepting the most innocent, are their secret allies against the systems of the second kind, and without themselves being openly at war with the latter, suddenly and unexpectedly do great mischief in their province. Besides, the attempt which is aimed at by the enlistment referred to of the services of the systems of the first kind by the second—the attempt to add an inner authentication to a system whose original authentication was external, is in its nature perilous; for, if it were capable of such an authentication, it would never have required an external one.