In Demonstration 3, Irenaeus writes:
Now, that we may not suffer ought of this kind, we must needs hold the rule of the faith without deviation, and do the commandments of God, believing in God and fearing Him as Lord and loving Him as Father. Now this doing is produced by faith: for Isaiah says:
If ye believe not, neither shall ye understand. And faith is produced by the truth; for faith rests on things that truly are. For in things that are, as they are, we believe; and believing in things that are, as they ever are, we keep firm our confidence in them. Since then faith is the perpetuation of our salvation, we must needs bestow much pains on the maintenance thereof, in order that we may have a true comprehension of the things that are. Now faith occasions this for us; even as the Elders, the disciples of the Apostles, have handed down to us.
“Even as the Elders…have handed down to us.” Now, this sounds like “tradition.” But, as always with that weasel-word, one must be careful to specify what it means, and we have to do so here from what Irenaeus himself says. Does it mean a secret, esoteric body of teachings that goes beyond what is written? Or does it mean the transmission of the content of what has been written–i.e., the “Apostolic preaching”?
In the post linked above, we saw that it meant basically the baptismal creed, which served as a summary of the story of Holy Scripture–it meant, in other words, the gospel.
We can observe something similar here. For Irenaeus goes on:
First of all it bids us bear in mind that we have received baptism for the remission of sins, in the name of God the Father, and in the name of Jesus Christ, the Son of God, who was incarnate and died and rose again, and in the Holy Spirit of God. And that this baptism is the seal of eternal life, and is the new birth unto God, that we should no longer be the sons of mortal men, but of the eternal and perpetual God; and that what is everlasting and continuing is made God; 1 and is over all things that are made, and all things are put under Him; and all the things that are put under Him are made His own; for God is not ruler and Lord over the things of another, but over His own; and all things are God’s; and therefore God is Almighty, and all things are of God. (Demonstration 3)
The shape of Irenaeus’ tradition is trinitarian, 2 and centers especially on the Trinity’s works ad extra: creation, redemption, and the Spirit’s application of redemption. After giving a series of Scriptural glosses on the persons of the Trinity, Irenaeus emphasizes the essential instrumental role of revelation in salvation:
Now the Spirit shows forth the Word, and therefore the prophets announced the Son of God; and the Word utters the Spirit, and therefore is Himself the announcer of the prophets, and leads and draws man to the Father.
The “tradition,” then, turns out to be the trinitarian rule of faith, which is drawn from the teaching of the prophets and apostles. Irenaeus comments further:
This then is the order of the rule of our faith, and the foundation of the building, and the stability of our conversation: God, the Father, not made, not material, invisible; one God, the creator of all things: this is the first point of our faith. The second point is: The Word of God, Son of God, Christ Jesus our Lord, who was manifested to the prophets according to the form of their prophesying and according to the method of the dispensation of the Father: through whom all things were made; who also at the end of the times, to complete and gather up all things, was made man among men, visible and tangible, in order to abolish death and show forth life and produce a community of union between God and man. And the third point is: The Holy Spirit, through whom the prophets prophesied, and the fathers learned the things of God, and the righteous were led forth into the way of righteousness; and who in the end of the times was poured out in a new way a upon mankind in all the earth, renewing man unto God.
And for this reason the baptism of our regeneration proceeds through these three points: God the Father bestowing on us regeneration through His Son by the Holy Spirit. For as many as carry (in them) the Spirit of God are led to the Word, that is to the Son; and the Son brings them to the Father; and the Father causes them to possess incorruption. Without the Spirit it is not possible to behold the Word of God, nor without the Son can any draw near to the Father for the knowledge of the Father is the Son, and the knowledge of the Son of God is through the Holy Spirit; and, according to the good pleasure of the Father, the Son ministers and dispenses the Spirit to whomsoever the Father wills and as He wills. (Demonstration 5ff.)
There is no esoteric other; the tradition is the gospel, the good news of salvation worked by the strong hand and outstretched arm of Almighty God. Thus it makes perfect sense that the balance of the treatise is a guided tour of how the story of Scripture unfolds, coming finally to salvation in the name of Jesus Christ (Demonstration 96-7). Afterwards, Irenaeus summarizes what he has done in a section that, together with the ones previously quoted, brackets what amounts to an extended disquisition on the unity of the content of revelation:
This, beloved, is the preaching of the truth, and this is the manner of our redemption, and this is the way of life, which the prophets proclaimed, and Christ established, and the apostles delivered, and the Church in all the world hands on to her children. This must we keep with all certainty, with a sound will and pleasing to God, with good works and right-willed disposition. (Demonstration 98)
What, then, is “tradition”? It is the truth, it is the redemption, it is the life “which the prophets proclaimed, and Christ established, and the apostles delivered, and the Church in all the world hands on to her children.” That is all it is, it is nothing more. But it is enough, and more than enough.