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

True doctrine must be tested against the apostolic churches that are in communion with one another

If, then, these things are so, it is in the same degree manifest that all doctrine which agrees with the apostolic churches—those moulds and original sources of the faith must be reckoned for truth, as undoubtedly containing that which the (said) churches received from the apostles, the apostles from Christ, Christ from God.  Whereas all doctrine must be prejudged as false which savors of contrariety to the truth of the churches and apostles of Christ and God. It remains, then, that we demonstrate whether this doctrine of ours, of which we have now given the rule, has its origin in the tradition of the apostles, and whether all other doctrines do not ipso facto proceed from falsehood. We hold communion with the apostolic churches because our doctrine is in no respect different from theirs. This is our witness of truth.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXI

Only those churches established by the Apostles and their line of succession can be apostolic

…after first bearing witness to the faith in Jesus Christ throughout Judæa, and founding churches (there), they next went forth into the world and preached the same doctrine of the same faith to the nations. They then in like manner founded churches in every city, from which all the other churches, one after another, derived the tradition of the faith, and the seeds of doctrine, and are every day deriving them, that they may become churches. Indeed, it is on this account only that they will be able to deem themselves apostolic, as being the offspring of apostolic churches.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XX

Scripture cannot be properly interpreted outside the Apostolic churches

Our appeal, therefore, must not be made to the Scriptures; nor must controversy be admitted on points in which victory will either be impossible, or uncertain, or not certain enough. But even if a discussion from the Scriptures should not turn out in such a way as to place both sides on a par, (yet) the natural order of things would require that this point should be first proposed, which is now the only one which we must discuss: “With whom lies that very faith to which the Scriptures belong. From what and through whom, and when, and to whom, has been handed down that rule, by which men become Christians?” For wherever it shall be manifest that the true Christian rule and faith shall be, there will likewise be the true Scriptures and expositions thereof, and all the Christian traditions.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XIX

A synopsis of the Apostolic faith

Now, with regard to this rule of faith—that we may from this point acknowledge what it is which we defend—it is, you must know, that which prescribes the belief that there is one only God, and that He is none other than the Creator of the world, who produced all things out of nothing through His own Word, first of all sent forth; that this Word is called His Son, and, under the name of God, was seen “in diverse manners” by the patriarchs, heard at all times in the prophets, at last brought down by the Spirit and Power of the Father into the Virgin Mary, was made flesh in her womb, and, being born of her, went forth as Jesus Christ; thenceforth He preached the new law and the new promise of the kingdom of heaven, worked miracles; having been crucified, He rose again the third day; (then) having ascended into the heavens, He sat at the right hand of the Father; sent instead of Himself the Power of the Holy Ghost to lead such as believe; will come with glory to take the saints to the enjoyment of everlasting life and of the heavenly promises, and to condemn the wicked to everlasting fire, after the resurrection of both these classes shall have happened, together with the restoration of their flesh. This rule, as it will be proved, was taught by Christ, and raises amongst ourselves no other questions than those which heresies introduce, and which make men heretics.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XIII

Christ, the God-man, descended to the dead

Now although Christ is God, yet, being also man, “He died according to the Scriptures,” and “according to the same Scriptures was buried.” With the same law of His being He fully complied, by remaining in Hades in the form and condition of a dead man; nor did He ascend into the heights of heaven before descending into the lower parts of the earth, that He might there make the patriarchs and prophets partakers of Himself. (This being the case), you must suppose Hades to be a subterranean region, and keep at arm’s length those who are too proud to believe that the souls of the faithful deserve a place in the lower regions. These persons, who are “servants above their Lord, and disciples above their Master,” would no doubt spurn to receive the comfort of the resurrection, if they must expect it in Abraham’s bosom. But it was for this purpose, say they, that Christ descended into hell, that we might not ourselves have to descend thither. Well,

Tertullian
A Treatise on the Soul
Chapter LV

Masses for the dead, fasting, kneeling and the sign of the cross during worship

As often as the anniversary comes round, we make offerings for the dead as birthday honors. We count fasting or kneeling in worship on the Lord’s day to be unlawful. We rejoice in the same privilege also from Easter to Whitsunday. We feel pained should any wine or bread, even though our own, be cast upon the ground.  At every forward step and movement, at every going in and out, when we put on our clothes and shoes, when we bathe, when we sit at table, when we light the lamps, on couch, on seat, in all the ordinary actions of daily life, we trace upon the forehead the sign.

If, for these and other such rules, you insist upon having positive Scripture injunction, you will find none. Tradition will be held forth to you as the originator of them, custom as their strengthener, and faith as their observer. That reason will support tradition, and custom, and faith, you will either yourself perceive, or learn from some one who has.

…This instances, therefore, will make it sufficiently plain that you can vindicate the keeping of even unwritten tradition established by custom; the proper witness for tradition when demonstrated by long-continued observance.

Tertullian
The Chaplet
Chapter III and IV