In his role as learned bishop of Milan in the 4th century, Saint Ambrose published this work concerning the holy trinity of Christ, God and the Holy Spirit.

Though not formally educated or trained in a university or seminary, St. Ambrose possessed gifts of intuition for matters of faith. His studies spanned wide, and he duly gained recognition and prominence as a scholar of great understanding and faith. Setting out to first define the tenets of the Christian Holy Trinity, Ambrose here uses his knowledge of Bible texts to support clear and well-founded explanation of what the holy spirit is and its subtle influence upon believers.

The establishment of a clear theology was a great concern of the early figures in Christianity. St. Ambrose spent years battling the rival doctrines of Arianism, at one point almost losing his own church to the movement. Eventually, he and fellow believers overcame the Arian faith; many of the writings and actions of St. Ambrose led to the formation of the Catholic church.