Tertullian · a new plain-English translation from the original language
Rather, let us be mindful both of the Lord's own pronouncements and of the apostolic writings, which foretold to us that heresies would come and marked out beforehand that they were to be fled; and just as we are not alarmed that they exist, so let us not marvel at the power that makes them things to be fled from in the first place. [2] The Lord instructs us that many will come in sheep's clothing, ravening wolves. [3] What are these sheep's clothes but the outward surface of the Christian name? What are these ravening wolves but treacherous minds and spirits, lurking within to prey upon the flock of Christ? [4] Who are the false prophets but false preachers? Who the false apostles but adulterating evangelists? Who the antichrists, both now and always, but rebels against Christ? [5] Such is what heresies will be, harassing the church no less by the perversity of their new teachings than antichrist himself, at that time, will persecute her with the savagery of persecutions—except that persecution makes martyrs, while heresy makes only apostates. [6] And so heresies too had to exist, that all who were approved might be shown for what they were—both those who stood firm in persecutions and those who did not swerve aside into heresies. [7] For he does not mean us to understand as approved those who alter their faith into heresy, as some interpret it in the opposite sense from what he says elsewhere: 'test all things, hold fast what is good'—as though it were permissible for everyone, having tested badly, to stumble by mistake into the choice of some evil.