What Can We Learn in the Letters to the Seven Churches?

Dr. Constantinou continues her exploration of the Book of Revelation. She discusses the opening vision and the letters to the seven churches, chapters 2 and 3. What do we learn about the context of Revelation from the vision of John described in Chapter 1? Why is the Holy Spirit described as the "seven spirits" before the throne of God? What was happening during the sixth and seventh centuries that led to the first Greek commentaries on the Apocalypse?