A restoration of the true Church is impossible

In whatever manner error came, it reigned of course only as long as there was an absence of heresies? Truth had to wait for certain Marcionites and Valentinians to set it free. During the interval the gospel was wrongly preached; men wrongly believed; so many thousands were wrongly baptized; so many works of faith were wrongly wrought; so many miraculous gifts, so many spiritual endowments, were wrongly set in operation; so many priestly functions, so many ministries, were wrongly executed; and, to sum up the whole, so many martyrs wrongly received their crowns! Else, if not wrongly done, and to no purpose, how comes it to pass that the things of God were on their course before it was known to what God they belonged? that there were Christians before Christ was found? that there were heresies before true doctrine? Not so; for in all cases truth precedes its copy, the likeness succeeds the reality. Absurd enough, however, is it, that heresy should be deemed to have preceded its own prior doctrine, even on this account, because it is that (doctrine) itself which foretold that there should be heresies against which men would have to guard! To a church which possessed this doctrine, it was written—yea, the doctrine itself writes to its own church—“Though an angel from heaven preach any other gospel than that which we have preached, let him be accursed.”

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXIX

It’s impossible for the Apostolic churches to have apostatized into the same exact faith

Grant, then, that all have erred; that the apostle was mistaken in giving his testimony; that the Holy Ghost had no such respect to any one (church) as to lead it into truth, although sent with this view by Christ, and for this asked of the Father that He might be the teacher of truth; grant, also, that He, the Steward of God, the Vicar of Christ, neglected His office, permitting the churches for a time to understand differently, (and) to believe differently, what He Himself was preaching by the apostles,—is it likely that so many churches, and they so great, should have gone astray into one and the same faith?  No casualty distributed among many men issues in one and the same result. Error of doctrine in the churches must necessarily have produced various issues.  When, however, that which is deposited among many is found to be one and the same, it is not the result of error, but of tradition. Can any one, then, be reckless enough to say that they were in error who handed on the tradition?

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXVIII

The Holy Spirit revealed all truth to the Apostles so that they needed no further revelation of truth

He had once said, “I have yet many things to say unto you, but ye cannot hear them now;” but even then He added, “When He, the Spirit of truth, shall come, He will lead you into all truth.” He (thus) shows that there was nothing of which they were ignorant, to whom He had promised the future attainment of all truth by help of the Spirit of truth.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXII

Heretics add and subtract from Scripture, and come up with new interpretations

Now this heresy of yours does not receive certain Scriptures; and whichever of them it does receive, it perverts by means of additions and diminutions, for the accomplishment of it own purpose; and such as it does receive, it receives not in their entirety; but even when it does receive any up to a certain point as entire, it nevertheless perverts even these by the contrivance of diverse interpretations. Truth is just as much opposed by an adulteration of its meaning as it is by a corruption of its text. Their vain presumptions must needs refuse to acknowledge the (writings) whereby they are refuted. They rely on those which they have falsely put together, and which they have selected, because of their ambiguity. Though most skilled in the Scriptures, you will make no progress, when everything which you maintain is denied on the other side, and whatever you deny is (by them) maintained. As for yourself, indeed, you will lose nothing but your breath, and gain nothing but vexation from their blasphemy.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XVII

Heresies always arise out of a twisting of the Scriptures

When men, therefore, are not Christians even on their own admission, how much more (do they fail to appear such) to us! What sort of truth is that which they patronize, when they commend it to us with a lie?  Well, but they actually treat of the Scriptures and recommend (their opinions) out of the Scriptures! To be sure they do. From what other source could they derive arguments concerning the things of the faith, except from the records of the faith?

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XIV

The Church will never be overcome by heresies

Heresies, at the present time, will no less rend the church by their perversion of doctrine, than will Antichrist persecute her at that day by the cruelty of his attacks, except that persecution make seven martyrs, (but) heresy only apostates. And therefore “heresies must needs be in order that they which are approved might be made manifest,” both those who remained stedfast under persecution, and those who did not wander out of their way into heresy.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter IV

Heresies all come after the Apostolic tradition

Nor need we wonder if the speculations of philosophers have perverted the older Scriptures. Some of their brood, with their opinions, have even adulterated our new-given Christian revelation, and corrupted it into a system of philosophic doctrines, and from the one path have struck off many and inexplicable by-roads.145 And I have alluded to this, lest any one becoming acquainted with the variety of parties among us, this might seem to him to put us on a level with the philosophers, and he might condemn the truth from the different ways in which it is defended. But we at once put in a plea in bar against these tainters of our purity, asserting that this is the rule of truth which comes down from Christ by transmission through His companions, to whom we shall prove that those devisers of different doctrines are all posterior. Everything opposed to the truth has been got up from the truth itself, the spirits of error carrying on this system of opposition.

Tertullian
Apology
Chapter XLVII

The cause of skepticism

The causes productive of skepticism are two things principally. One is the changefulness and instability of the human mind, whose nature it is to generate dissent, either that of one with another, or that of people with themselves. And the second is the discrepancy which is in things; which, as to be expected, is calculated to be productive of skepticism.

Clement of Alexandria
The Stromata, Book VIII
Chaper VII

The Catholic Church is one tradition not named after a man or a place

Therefore in substance and idea, in origin, in pre-eminence, we say that the ancient and Catholic Church is alone, collecting as it does into the unity of the one faith— which results from the peculiar Testaments, or rather the one Testament in different times by the will of the one God, through one Lord— those already ordained, whom God predestinated, knowing before the foundation of the world that they would be righteous. But the pre-eminence of the Church, as the principle of union, is, in its oneness, in this surpassing all things else, and having nothing like or equal to itself. But of this afterwards. Of the heresies, some receive their appellation from a [person’s] name, as that which is called after Valentinus, and that after Marcion, and that after Basilides, although they boast of adducing the opinion of Matthew [without truth]; for as the teaching, so also the tradition of the apostles was one. Some take their designation from a place, as the Peratici; some from a nation, as the [heresy] of the Phrygians; some from an action, as that of the Encratites; and some from peculiar dogmas, as that of the Docetæ;, and that of the Hærmatites; and some from suppositions, and from individuals they have honoured, as those called Cainists, and the Ophians; and some from nefarious practices and enormities, as those of the Simonians called Entychites.

Clement of Alexandria
The Stromata, Book VII
Chapter XVII

Heresies ignore the traditions and generate their own dogma

And as those almonds are called empty in which the contents are worthless, not those in which there is nothing; so also we call those heretics empty, who are destitute of the counsels of God and the traditions of Christ; bitter, in truth, like the wild almond, their dogmas originating with themselves, with the exception of such truths as they could not, by reason of their evidence, discard and conceal.

Clement of Alexandria
The Stromata, Book VII
Chapter XVI