De Fide and De Spiritu Sancto

De Fide and De Spiritu Sancto are the chief dogmatic works of Saint Ambrose of Milan. Composed between 378 and 381 at the request of the Emperor Gratian, they vindicate the Divinity of Christ and of the Holy Spirit against those who would deny them. Saint Ambrose (Aurelius Ambrosius) was bishop of Milan from a.d. 374 to 397 and was one of the most influential ecclesiastical figures of the fourth century. For his brilliant defense of orthodoxy against the Arian heretics, Saint Ambrose is counted as one of the four original Doctors of the Church.