For there must be also heresies among you, that they which are approved may be made manifest among you.
Ver. 19. There must be heresies] Therefore much more schisms, which also, for the most part, do degenerate into heresies; as an old serpent into a dragon. In the time of Pope Clement V, Frederick, king of Sicily, was so offended at the evil govermnent of the Church, that he began to question the truth of the Christian religion. But Arnoldus de Villanova confirmed and settled him by this and such like places of Scripture, "Offences must come, there must be heresies," &c., God having so decreed and foretold it. It behoves that there be heresies in the Church; as it is necessary there should be poison and venomous creatures in the world, because out of them God will work medicines.
May be made manifest] As they are now, if ever, in these shedding and discriminating times. So in the Palatinate they fell to Popery, as fast as leaves in autumn.