On the authority of the Church as regards to discerning truth from heresy… that the doctrine of the church is universal and verifiable as apostolic can be easily seen...
It is within the power of all, therefore, in every Church, who may wish to see the truth, to contemplate clearly the tradition of the apostles manifested throughout the whole world; and we are in a position to reckon up those who were by the apostles instituted bishops in the Churches, and [to demonstrate] the succession of these men to our own times; those who neither taught nor knew of anything like what these [heretics] rave about. (3.1)
Rome as having preeminent authority...
Since, however, it would be very tedious, in such a volume as this, to reckon up the successions of all the Churches, we do put to confusion all those who, in whatever manner, whether by an evil self-pleasing, by vainglory, or by blindness and perverse opinion, assemble in unauthorized meetings; [we do this, I say,] by indicating that tradition derived from the apostles, of the very great, the very ancient, and universally known Church founded and organized at Rome by the two most glorious apostles, Peter and Paul; as also [by pointing out] the faith preached to men, which comes down to our time by means of the successions of the bishops. For it is a matter of necessity that every Church should agree with this Church, on account of its preeminent authority. (3.2)
Proceeds to go through the succession (3.3)…
Peter and Paul… Linus… Anacletus… Clement… Evaristus… alexander… Sixtus (sixth from the Apostles)... Telephorus… Hyginius… Pius… anicetus...Eleutherius…
Appeals to the letter of S Clement as a proper measure of the doctrine of the Apostles as opposed to newer doctrines of the heretics (also to S ignatius to the Philippians).
… and after him, in the third place from the apostles, Clement was allotted the bishopric. This man, as he had seen the blessed apostles, and had been conversant with them, might be said to have the preaching of the apostles still echoing [in his ears], and their traditions before his eyes.
In the time of this Clement, no small dissension having occurred among the brethren at Corinth, the Church in Rome dispatched a most powerful letter to the Corinthians, exhorting them to peace, renewing their faith, and declaring the tradition which it had lately received from the apostles […] From this document, whosoever chooses to do so, may learn that He, the Father of our Lord Jesus Christ, was preached by the Churches, and may also understand the apostolic tradition of the Church, since this Epistle is of older date than these men who are now propagating falsehood, and who conjure into existence another god beyond the Creator and the Maker of all existing things.
Knew S Polycarp in his youth… relates how he and S John dealt with heretics…
There are also those who heard from him that John, the disciple of the Lord, going to bathe at Ephesus, and perceiving Cerinthus within, rushed out of the bath-house without bathing, exclaiming, Let us fly, lest even the bath-house fall down, because Cerinthus, the enemy of the truth, is within. And Polycarp himself replied to Marcion, who met him on one occasion, and said, Do you know me? I do know you, the first-born of Satan. Such was the horror which the apostles and their disciples had against holding even verbal communication with any corrupters of the truth; as Paul also says, A man that is an heretic, after the first and second admonition, reject; knowing that he that is such is subverted, and sins, being condemned of himself. Titus 3:10 (3.4)
The Church is described as having the deposit of faith…
In Chapter 4
Since therefore we have such proofs, it is not necessary to seek the truth among others which it is easy to obtain from the Church; since the apostles, like a rich man [depositing his money] in a bank, lodged in her hands most copiously all things pertaining to the truth: so that every man, whosoever will, can draw from her the water of life. [Revelation 22:17] For she is the entrance to life; all others are thieves and robbers. On this account are we bound to avoid them, but to make choice of the thing pertaining to the Church with the utmost diligence, and to lay hold of the tradition of the truth.
The same continued… We are to settle differences in the interpretation of Sacred Scripture as we would had scriptures not been handed down… by appeal to tradition.
For how stands the case? Suppose there arise a dispute relative to some important question among us, should we not have recourse to the most ancient Churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings? Would it not be necessary, [in that case,] to follow the course of the tradition which they handed down to those to whom they did commit the Churches? (4.1)
He sums things up in Chapter 24 (the other book end).
The Holy Spirit preserves the deposit of faith through the Church--an excellent vessel--from which we receive it which it also renews.
But [it has, on the other hand, been shown], that the preaching of the Church is everywhere consistent, and continues in an even course, and receives testimony from the prophets, the apostles, and all the disciples— as I have proved— through [those in] the beginning, the middle, and the end, and through the entire dispensation of God, and that well-grounded system which tends to man's salvation, namely, our faith; which, having been received from the Church, we do preserve, and which always, by the Spirit of God, renewing its youth, as if it were some precious deposit in an excellent vessel, causes the vessel itself containing it to renew its youth also. For this gift of God has been entrusted to the Church, as breath was to the first created man, for this purpose, that all the members receiving it may be vivified; and the [means of] communion with Christ has been distributed throughout it, that is, the Holy Spirit, the earnest of incorruption, the means of confirming our faith, and the ladder of ascent to God. (24.1)
Those who do not partake in this defraud themselves.
For in the Church, it is said, God has set apostles, prophets, teachers, [1 Corinthians 12:28] and all the other means through which the Spirit works; of which all those are not partakers who do not join themselves to the Church, but defraud themselves of life through their perverse opinions and infamous behaviour. For where the Church is, there is the Spirit of God; and where the Spirit of God is, there is the Church, and every kind of grace; but the Spirit is truth. Those, therefore, who do not partake of Him, are neither nourished into life from the mother's breasts, nor do they enjoy that most limpid fountain which issues from the body of Christ; but they dig for themselves broken cisterns Jeremiah 2:13 out of earthly trenches, and drink putrid water out of the mire, fleeing from the faith of the Church lest they be convicted; and rejecting the Spirit, that they may not be instructed.
In 4.3 he gives a brief history of the gnostic heresies.
In 6.1 he affirms S Justin’s view that the Son spoke with Abraham.
In 11.1 he observes that S John’s gospel was written as it was to counter the error of one Cerinthus (an gnostic Ebionite contemporary of S John) , to the effect that the Father and the creator are distinct gods and that Christ was distinct from Jesus (Christ being said to have dwelt in Jesus from the time of his baptism to just before his suffering--that Christ was never incarnate and never suffered--a rejection of the goodness of creation).
In 21 Christ is affirmed as the New Adam… a connection essential to redemption… An analogy is made between the virgin soil from which Adam came and the virginity of Mary… and why the second Adam must come not again from virgin soil but from a virgin (The immaculate character of Our Lady is implied here in seed form at least.)
For as by one man's disobedience sin entered, and death obtained [a place] through sin; so also by the obedience of one man, righteousness having been introduced, shall cause life to fructify in those persons who in times past were dead. Romans 5:19 And as the protoplast himself Adam, had his substance from untilled and as yet virgin soil (for God had not yet sent rain, and man had not tilled the ground Genesis 2:5), and was formed by the hand of God, that is, by the Word of God, for all things were made by Him, John 1:3 and the Lord took dust from the earth and formed man; so did He who is the Word, recapitulating Adam in Himself, rightly receive a birth, enabling Him to gather up Adam [into Himself], from Mary, who was as yet a virgin. If, then, the first Adam had a man for his father, and was born of human seed, it were reasonable to say that the second Adam was begotten of Joseph. But if the former was taken from the dust, and God was his Maker, it was incumbent that the latter also, making a recapitulation in Himself, should be formed as man by God, to have an analogy with the former as respects His origin. Why, then, did not God again take dust, but wrought so that the formation should be made of Mary? It was that there might not be another formation called into being, nor any other which should [require to] be saved, but that the very same formation should be summed up [in Christ as had existed in Adam], the analogy having been preserved. (21.10)
Mary as the New Eve… the first extant articulation of this connection...
In accordance with this design, Mary the Virgin is found obedient, saying, Behold the handmaid of the Lord; be it unto me according to your word. [Luke 1:38] But Eve was disobedient; for she did not obey when as yet she was a virgin. And even as she, having indeed a husband, Adam, but being nevertheless as yet a virgin (for in Paradise they were both naked, and were not ashamed, [Genesis 2:25] inasmuch as they, having been created a short time previously, had no understanding of the procreation of children: for it was necessary that they should first come to adult age, and then multiply from that time onward), having become disobedient, was made the cause of death, both to herself and to the entire human race; so also did Mary, having a man betrothed [to her], and being nevertheless a virgin, by yielding obedience, become the cause of salvation, both to herself and the whole human race. […] And thus also it was that the knot of Eve's disobedience was loosed by the obedience of Mary. For what the virgin Eve had bound fast through unbelief, this did the virgin Mary set free through faith. (22.4)
On the prophecy that Christ will be born of a virgin, this translation is upheld by the unanimity of the 70 Jewish translators of the Septuagint, whose translations were given under the direction of Ptolemy prior to the advent of Christ.
But it was interpreted into Greek by the Jews themselves, much before the period of our Lord's advent, that there might remain no suspicion that perchance the Jews, complying with our humour, did put this interpretation upon these words. They indeed, had they been cognizant of our future existence, and that we should use these proofs from the Scriptures, would themselves never have hesitated to burn their own Scriptures… (21.1)
But when they came together in the same place before Ptolemy, and each of them compared his own interpretation with that of every other, God was indeed glorified, and the Scriptures were acknowledged as truly divine. For all of them read out the common translation [which they had prepared] in the very same words and the very same names, from beginning to end, so that even the Gentiles present perceived that the Scriptures had been interpreted by the inspiration of God. (21.2)
The translations as Divinely inspired…
For the one and the same Spirit of God, who proclaimed by the prophets what and of what sort the advent of the Lord should be, did by these elders give a just interpretation of what had been truly prophesied… (21.4)