I. Shema Is Not Enough: The Indispensability of the Doctrine of the Trinity
Trinity speaks about God in light of Jesus Christ
Trinity guards our appreciation of the God of Israel and Jesus Christ
Trinity guides our further exploration of God and God's works

II. Origins of the Doctrine of the Trinity
Old Testament hints (Gen. 18:1-16, Is. 6:3, Ps. 33:6, Prov. 8, Gen. 1:1-3, :26)
Jesus' career brings God's threeness into plain view
The doctrine develops as Jews worship the risen Jesus

III. Jesus' Special Status
1. Jesus calls God "the Father" (abba/ho pater; Matt. 11:27)
2. Jesus calls himself "the (only) Son": John 3:16, Rom. 8:32, Col. 1:13
3. Jesus reveals the Father (John 14:9) as "only begotten God" (John 1:18)
4. Jesus is Creator (John 1, 1 Cor. 8:5-6, Col. 1:16), Judge, and Savior
5. Believers confess that "Jesus is Lord" (Phil. 2:11, cf. Isa. 45:23; 1 Cor. 16:22)

IV. The Role of the Holy Spirit
1. The Spirit proceeds from the Father (John 15:26)
2. The Spirit conceives Jesus (Luke 1:35)
3. Jesus receives the Spirit from the Father (Luke 3:22, Acts 2:33)
4. Jesus gives the Spirit to humanity (Acts 2:33, John 14:16, 26, John 20:22)

V. Divine Triads in the Bible
Explicit: Matt. 28:19, 2 Cor. 13:13
Subtle: Luke 1:35, Luke 24:49, Ro. 14:17-18, Ro. 15:16, Ro. 15:30, 1 Cor. 12:4-6, 2 Cor. 1:21-22, 2 Cor. 3:3, Gal. 3:11-14, Gal. 4:6, Eph. 2:18, Eph. 2:20-22, Eph. 3:14-16, Phil. 3:3, Col. 1:6-8, 2 Th. 2:13, Tit 3:4-6, Heb. 6:4-6, 1 Pet. 1:2, 1 Pet. 4:14, 1 John 4:2, 1 John 4:13-14
Conclusion: Trinity is rooted in history, Scripture, and Christian experience

VII. Beyond Prooftexting: Further Development in Christian Tradition
Trinitarian language develops to speak of God properly in:
Worship practice (liturgy)
Initiation (baptism) and confession (creeds)
Intellectual reflection ("theology")
Arguments against adversaries (polemics, apologetics)
Conclusions: Two models of God

VIII. Greek Christianity: The Cappadocian ("Social") Trinity
The unity of the divine persons is relational
The Father is the source of divinity and unity
Interrelationships constitute the Father as Father, Son as Son, Spirit as Spirit
Coinherence (three turned-in-mirrors) / perichoresis (the divine dance)
Rublev's Trinity

IX. Latin Christianity: The Augustinian ("Psychological") Trinity
The persons are one in sharing the divine essence
The relations among the divine persons resemble those of our interior selves
Lover, beloved, love
Memory, intellect, will
Western Trinitarian iconography
The Filioque: the Spirit proceeds "also from the Son"

X. What Is a Person? Basic Trinitarian Vocabulary
Greek: ousia (1); prosopon, hypostasis (3)
Latin: esse, substantia,(1); persona, subsistentia (3)
English: being, substance (1); person, subsistence, "way of being" (3)
1. The terms become confused in translation
2. Begetting and proceeding distinguish the persons
3. Modern understandings of "person" differ; is God one modern "person"? Three? Zero?
4. Context is crucial!

XI. Conclusion: Real Christians Struggling With Real Issues