Pope St. Celestine I (d. 432 A.D.) was a Roman deacon who was elected Supreme Pontiff in 422 A.D. He was a contemporary of St. Augustine, and it is said that the two were good friends. He also lived with St. Ambrose in Milan prior to serving in Rome. Pope St. Celestine lead the Church for nine years during a troubled time of social upheaval. Within the Church there were multiple dangerous heresies spreading and corrupting the faith of the people, especially Nestorianism and Pelagianism, which he staunchly fought against, and for this he is known as a defender of orthodox doctrine. Outside the Church, barbarian hordes were invading the West, leading to the collapse of the Roman Empire. Pope St. Celestine I worked to restore the churches that were attacked when Alaric the Goth sacked Rome. He also established the papal diplomatic service to send ambassadors, known as nuncios, from the Vatican to other governments around the world. He is also the Holy Father who sent St. Patrick to evangelize Ireland, and who introduced the responsorial psalm into the papal Mass at Rome. His feast day is July 27th.