11 “But, hidden wolves,” you will say, “clad in sheep's clothing, and privily and grievously wasting the Lord's flock, can we no otherwise find out.” Whence then have the Priscillianists become known, ere this way of hunting for them with lies was ex-cogitated? Whence was their very author, more cunning doubtless, and therefore more covert, got at in his bed? Whence so many and so great persons made manifest and condemned, and the others innumerable partly corrected, partly as if corrected, and in the Church's compassion gathered into her fold?
For many ways gives the Lord, when He has compassion, whereby we may come to the discovery of them: two of which are more happy than others; namely, that either they whom they have wished to seduce, or they whom they had already seduced, shall, when they repent and are converted, point them out. Which is more easily effected, if their nefarious error, not by lying tricks, but by truthful reasonings be overthrown. In the writing of which it behooves you to bestow your pains, since God has bestowed the gift that you can do this: which wholesome writings whereby their insane perversity is destroyed, becoming more and more known, and being by Catholics, whether prelates who speak in the congregations, or any studious men full of zeal for God, every where diffused, these will be holy nets in which they may be caught truthfully, not with lies hunted after.
For so being taken, either, of their own accord, they will confess what they have been, and others whom they know to be of the evil fellowship they will either kindly correct, or mercifully betray. Or else, if they shall be ashamed to confess what with long-continued simulation they have concealed, by the hidden hand of God healing them shall they be made whole.
Source: To Consentius: Against Lying (New Advent)