This book listens to him as he writes to his friends in Philippi, to attempt to understand the experience of joy that more than mere emotion. Paul highlights four reasons why joy fills his heart: because of the Gospel partnership he shares with his friends in Philippi; because of the unity that they experience in Christ; because of their confidence in Jesus; and because God has given them peace beyond understanding. These themes correspond with the four chapters of the letter, and form the organizing principle of this book.