Teaching theology classes is some of the most exhilarating things I've ever had the joy of doing. And teaching Trinity and Christology are why that's true.
In teaching Christology, I always draw together what I call my "12 grammatical rules".
I mention them here today because much of what I've been reading lately -- on preaching -- has had so much to contribute to thinking about Christian speech, that I think these bear repeating for pastors on occasion. (This post is really Karl Barth's "fault", since I just finished Dogmatics in Outline again this month.)
Each of these rules are offered here in both a negative and a positive affirmation. The negative addresses temptations of Christian speaking that don't speak of Jesus Christ biblically. These are temptations of preaching that preachers must avoid. The positive is the simple message of the Good News we proclaim.
1. Not to speak of Christ in any way that sidelines his human experience. Jesus Christ is truly human.
2. Not to speak of Jesus in any way that sidelines the divine depth beneath his human experience. Jesus Christ is truly God.
3. Not to divide Christ's divinity and humanity, or to give the impression that he sometimes functions as God and sometimes as a human. Jesus Christ is divine and human in one person.
4. Not to give the impression that Christ's divinity is fully contained within his humanity, or that his divinity is limited by his human experience. The human nature of Jesus is assumed by the person of the eternal Word.
5. Not to divide redemption from creation, or to give the impression that Christ invades a world that is alien to him. Human beings were created after the pattern of the same eternal Image that has become incarnate in Jesus.
6. Not to divide Christ's person and work, or to give the impression that Christ is merely the instrument by which God achieves salvation. Salvation is a person: Jesus Christ.
7. Not to divide Christ's life, death, and resurrection, or to give the impression that he achieves salvation at just one moment of his career. The total life-journey of Jesus Christ -- from his birth, to his ministry of teaching and healing, to his death and resurrection -- is the saving event.
8. Not to speak of Christ's death as a mere preliminary stage on the way to resurrection. Jesus Christ is the Priest whose death abolishes the power of sin and death. He is the humble God.
9. Not to speak of Christ's resurrection as a mere reversal of his death. Jesus Christ is the King whose resurrection exalts and glorifies human nature. He is the deified human.
10. Not to speak of Christ in any way that implies that he is absent, or to give the impression that the church's task is to make Christ present. Jesus Christ is the Prophet who reveals himself. He is present always and everywhere as the divine-human light of the world.
11. Not to divide Christ from Israel's history, or to give the impression that the New Testament abolishes the Old. As Prophet, Priest and King, Jesus Christ is the surpassing fulfilment of Israel's messianic hopes.
12. Not to speak of Christ as if he were relevant only to some people in some cultures and circumstances. Jesus Christ is present to all people, in all times and places, as their divine-human Prophet, Priest and King. The church trusts and proclaims, but never possesses, this Messiah.
All of this is to say that preachers should be reading some of our theological treasures on Christology often.
Irenaeus' Against Heresies and Athanasius' On the Incarnation especially.
But also some wide reading in Origen ("Wisdom", "Word" and "Image" are the key words here), Gregory of Nazianzus ("What he has not assumed, he has not healed"), Cyril of Alexandria ("The iron in the fire", on two natures, one person), Augustine ("singing in one voice", or the whole Jesus -- head and body), Anselm and Julian of Norwich (on satisfying God), John Calvin (the munus triplex -- Prophet-Priest-King), and of course Karl Barth (Reconciliation as "bringing us home").
See, this is why teaching theology is such fun.