Heretics lack discipline because they do not fear God

They say that God is not to be feared; therefore all things are in their view free and unchecked. Where, however is God not feared, except where He is not? Where God is not, there truth also is not. Where there is no truth, then, naturally enough, there is also such a discipline as theirs. But where God is, there exists “the fear of God, which is the beginning of wisdom.” Where the fear of God is, there is seriousness, an honourable and yet thoughtful diligence, as well as an anxious carefulness and a well-considered admission (to the sacred ministry)2296 and a safely-guarded communion, and promotion after good service, and a scrupulous submission (to authority), and a devout attendance, and a modest gait, and a united church, and God in all things.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XLIII

Heretics continue to schism and can’t agree among themselves

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 harboring 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.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XLII

The heretics either add gods in addition, or change the one God into something else

They either pretend that there is another god in opposition to the Creator, or, even if they acknowledge that the Creator is the one only God, they treat of Him as a different being from what He is in truth. The consequence is, that every lie which they speak of God is in a certain sense a sort of idolatry.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XL

Diversity of doctrine among the heretics is the mark of heresy

Where diversity of doctrine is found, there, then, must the corruption both of the Scriptures and the expositions thereof be regarded as existing. On those whose purpose it was to teach differently, lay the necessity of differently arranging the instruments of doctrine. They could not possibly have effected their diversity of teaching in any other way than by having a difference in the means whereby they taught. As in their case, corruption in doctrine could not possibly have succeeded without a corruption also of its instruments, so to ourselves also integrity of doctrine could not have accrued, without integrity in those means by which doctrine is managed. Now, what is there in our Scriptures which is contrary to us? What of our own have we introduced, that we should have to take it away again, or else add to it, or alter it, in order to restore to its natural soundness anything which is contrary to it, and contained in the Scriptures? What we are ourselves, that also the Scriptures are (and have been) from the beginning. Of them we have our being, before there was any other way, before they were interpolated by you.

…. One man perverts the Scriptures with his hand, another their meaning by his exposition. For although Valentinus seems to use the entire volume, he has none the less laid violent hands on the truth only with a more cunning mind and skill than Marcion. Marcion expressly and openly used the knife, not the pen, since he made such an excision of the Scriptures as suited his own subject-matter. Valentinus, however, abstained from such excision, because he did not invent Scriptures to square with his own subject-matter, but adapted his matter to the Scriptures; and yet he took away more, and added more, by removing the proper meaning of every particular word, and adding fantastic arrangements of things which have no real existence.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXXVIII

Heretics must prove that the orthodox lack continuity with the Apostolic faith

…since they deny the truth of (our doctrine), they ought to prove that it also is heresy, refutable by the same rule as that by which they are themselves refuted; and at the same time to show us where we must seek the truth, which it is by this time evident has no existence amongst them.  Our system is not behind any in date; on the contrary, it is earlier than all; and this fact will be the evidence of that truth which everywhere occupies the first place.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXXV

Heresies can’t prove their connection to the Apostolic faith

Let the entire mass of heresies choose, therefore, for themselves the times when they should appear, provided that the when be an unimportant point; allowing, too, that they be not of the truth, and (as a matter of course) that such as had no existence in the time of the apostles could not possibly have had any connection with the apostles. If indeed they had then existed, their names would be extant, with a view to their own repression likewise.  Those (heresies) indeed which did exist in the days of the apostles, are condemned in their very mention. If it be true, then, that those heresies, which in the apostolic times were in a rude form, are now found to be the same, only in a much more polished shape, they derive their condemnation from this very circumstance. Or if they were not the same, but arose afterwards in a different form, and merely assumed from them certain tenets, then, by sharing with them an agreement in their teaching, they must needs partake in their condemnation, by reason of the above-mentioned definition, of lateness of date, which meets us on the very threshold. Even if they were free from any participation in condemned doctrine, they would stand already judged on the mere ground of time, being all the more spurious because they were not even named by the apostles. Whence we have the firmer assurance, that these were (the heresies) which even then, were announced as about to arise.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXXIV

If the heretic’s faith is true, let him prove it by a record of Apostolic succession and full-communion status

But if there be any (heresies) which are bold enough to plant themselves in the midst of the apostolic age, that they may thereby seem to have been handed down by the apostles, because they existed in the time of the apostles, we can say: Let them produce the original records of their churches; let them unfold the roll of their bishops, running down in due succession from the beginning in such a manner that [that first bishop of theirs] bishop shall be able to show for his ordainer and predecessor some one of the apostles or of apostolic men,—a man, moreover, who continued stedfast with the apostles. For this is the manner in which the apostolic churches transmit their registers: as the church of Smyrna, which records that Polycarp was placed therein by John; as also the church of Rome, which makes Clement to have been ordained in like manner by Peter. In exactly the same way the other churches likewise exhibit (their several worthies), whom, as having been appointed to their episcopal places by apostles, they regard as transmitters of the apostolic seed. Let the heretics contrive something of the same kind.

….To this test, therefore will they be submitted for proof by those churches, who, although they derive not their founder from apostles or apostolic men (as being of much later date, for they are in fact being founded daily), yet, since they agree in the same faith, they are accounted as not less apostolic because they are akin in doctrine. Then let all the heresies, when challenged to these two tests by our apostolic church, offer their proof of how they deem themselves to be apostolic. But in truth they neither are so, nor are they able to prove themselves to be what they are not. Nor are they admitted to peaceful relations and communion by such churches as are in any way connected with apostles, inasmuch as they are in no sense themselves apostolic because of their diversity as to the mysteries of the faith.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXXII

Only the faith first delivered is truth. Everything that has come after is false.

Let me return, however, from this digression to discuss the priority of truth, and the comparative lateness of falsehood, deriving support for my argument even from that parable which puts in the first place the sowing by the Lord of the good seed of the wheat, but introduces at a later stage the adulteration of the crop by its enemy the devil with the useless weed of the wild oats.  For herein is figuratively described the difference of doctrines, since in other passages also the word of God is likened unto seed. From the actual order, therefore, it becomes clear, that that which was first delivered is of the Lord and is true, whilst that is strange and false which was afterwards introduced. This sentence will keep its ground in opposition to all later heresies, which have no consistent quality of kindred knowledge inherent in them—to claim the truth as on their side.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXXI

Preaching a new gospel would require Christ to come a second time; and that’s impossible before the end

There is, however, a certain man named Nigidius, and Hermogenes, and several others, who still pursue the course of perverting the ways of the Lord. Let them show me by what authority they come!  If it be some other God they preach, how comes it that they employ the things and the writings and the names of that God against whom they preach? If it be the same God, why treat Him in some other way? Let them prove themselves to be new apostles! Let them maintain that Christ has come down a second time, taught in person a second time, has been twice crucified, twice dead, twice raised! For thus has the apostle described (the order of events in the life of Christ); for thus, too, is He accustomed to make His apostles—to give them, (that is), power besides of working the same miracles which He worked Himself.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXX