The idea of the "Kingdom of God" is absolutely central to the Christian Gospel. The first words out of the mouth of Jesus in St. Mark's Gospel are “The time is fulfilled, and the kingdom of God is at hand; repent, and believe in the gospel” (Mark 1:15). St. Matthew says that Jesus "went about all Galilee, teaching in their synagogues and preaching the gospel of the kingdom and healing every disease and every infirmity among the people" (Mt. 4:23). And we pray for the coming of this Kingdom every time that we pray the Lord's Prayer. So what do we mean by the "Kingdom of God," and how should it impact our approach to the Church, to civil society, and to our own responsibilities?
Why do Catholics call their Church the "Catholic" Church? Why not just call it the Christian Church? Is the Catholicity of the Church important? Is it Biblical? What does it even mean to say that the Church is "Catholic"?