The blood of Priscillian was the seed of Priscillianism. But his disciples certainly went further than their master; they became thoroughgoing Manicheans. This explains St. Jerome's[1] and St. Augustine's[2] strong denunciations of the Spanish heresy. The gross errors of the Priscillianists in the fifth century attracted in 447 the attention of Pope St. Leo. He reproaches them for breaking the bonds of marriage, rejecting all idea of chastity, and contravening all rights, human and divine. He evidently held Priscillian responsible for all these teachings. That is why he rejoices in the fact that "the secular princes, horrified at this sacrilegious folly, executed the author of these errors with several of his followers." He even declares that this action of the State is helpful to the Church. He writes: "the Church, in the spirit of Christ, ought to denounce heretics, but should never put them to death; still the severe laws of Christian princes redound to her good, for some heretics, through fear of punishment, are won back to the true faith."[3] St. Leo in this passage is rather severe. "While he does not yet require the death penalty for heresy, he accepts it in the name of the public good. It is greatly to be feared that the churchmen of the future will go a great deal further." [1] _De Viris illustribus_, 121-123. [2] _De hæresibus_, cap. 70. [3] Ep. xv, _ad Turribium_, P.L., vol. liv, col. 679-680. The Church is endeavoring to state her position accurately on the suppression of heresy. She declares that nothing will justify her shedding of human blood. This is evident from the conduct and writings of St. Augustine, St. Martin, St. Ambrose, St. Leo (_cruentas refugit ultiones_), and Ithacius himself. But to what extent should she accept the aid of the civil power, when it undertakes to defend her teachings by force? Some writers, like St. Optatus of Mileve, and Priscillian, later on the victim of his own teaching, believed that the Christian State ought to use the sword against heretics guilty of crimes against the public welfare; and, strangely enough, they quote the Old Testament as their authority. Without giving his approval to this theory, St. Leo the Great did not condemn the practical application of it in the case of the Priscillianists. The Church, according to him, while assuming no responsibility for them, reaped the benefit of the rigorous measures taken by the State.