Irenaeus and the Starting Point of Theology

In The Demonstration of the Apostolic Preaching, Irenaeus presents "a manual of essentials" of the faith. In modern terms, this document might be called a systematic theology. One of the things I find fascinating about this is the way Irenaeus begins. Every theology has to have a starting point: a central fact from which the rest flows. This could be a philosophical argument for the existence of God, the inspiration of the Bible, God's self-revelation in nature or creation, the event of the Incarnation, the cross, etc.

Irenaeus, however, doesn't start with any of these. He begins with baptism:

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 (3).

Thus, theology doesn't begin with a proposition, a statement, or a thought; not even a statement about Christ or the cross. Rather, theology begins with an event: God's regeneration of us through the Holy Spirit, uniting us with the crucified Christ and His body, the church. I hope I am not wrong about this, but it seems like a big deal. It seems to be quite radical. Some implications I see:

• Theology is not about us understanding God but about God revealing Himself to us; not just in a general sense (Jesus reveals the Father to the world) but in a personal sense (God reveals Himself to me through the Holy Spirit).
• Belief can't be separated from action (as Irenaeus makes clear from the outset). Theology and practice are interdependent.
• Theology is a task of the church. It absolutely cannot be done elsewhere.

Having begun with baptism, Irenaeus uses the baptismal formula as the framework for what will follow. Being baptized in the name of the Father, the Son, and the Holy Spirit is more than just an affirmation of a prior belief in the Trinity. It is what we are baptized into and thus gives shape to everything we believe.