The Prescription Against Heretics by Tertullian
Chapter XLII.--Heretics Work to Pull Down and to Destroy, Not to Edify and Elevate Heretics Do Not Adhere Even to Their Own Traditions, But Harbour Dissent Even from Their Own Founders.
But what shall I say concerning the ministry of the word, since they make it their business not to convert the heathen, but to subvert our people? This is rather the glory which they catch at, to compass the fall of those who stand, not the raising of those who are down. Accordingly, since the very work which they purpose to themselves comes not from the building up of their own society, but from the demolition of the truth, they undermine our edifices, that they may erect their own. Only deprive them of the law of Moses, and the prophets, and the divinity of the Creator, and they have not another objection to talk about. The consequence is, that they more easily accomplish the ruin of standing houses than the erection of fallen ruins. It is only when they have such objects in view that they show themselves humble and bland and respectful. Otherwise they know no respect even for their own leaders. Hence it is [supposed] that schisms seldom happen among heretics, because, even when they exist, they are not obvious. Their very unity, however, is schism. I am greatly in error if they do not amongst themselves swerve even from their own regulations, forasmuch as every man, just as it suits his own temper, modifies the traditions he has received after the same fashion as the man who handed them down did, when he moulded them according to his own will. The progress of the matter is an acknowledgment at once of its character and of the manner of its birth. That was allowable to the Valentinians which had been allowed to Valentinus; that was also fair for the Marcionites which had been done by Marcion -- even to innovate on the faith, as was agreeable to their own pleasure. In short, all heresies, when thoroughly looked into, are detected harbouring dissent in many particulars even from their own founders. The majority of them have not even churches. Motherless, houseless, creedless, outcasts, they wander about in their own essential worthlessness.