What does it mean to be a citizen of heaven?

In this more informal talk on Philippians 3:17-4:1, the Rev. Kristen Yates asks what Paul means when he says the Philippians (and us by extension) are citizens of heaven? Rather than meaning that we should be people who disengage from culture because we belong to some other-worldly reality, it means that we are called to bring the Kingdom of God’s values to bear on our cultures.  (There is no manuscript for this talk).