3:15-16: How is the Church "the pillar and ground of truth"? What metaphor is Paul using? How does that metaphor help us understand what the Church does?
What does he mean when he speaks of "the house of God"? Does he mean the church as a whole or individual congregations?
What does Paul mean when he says "without controversy"?
To what is Paul referring with the word mystery? Why is the word mystery an appropriate reference for that case? (Verse 16 seems to be another quotation from a hymn.) What is Paul talking about when he says that Christ was seen by angels?