Few Catholics today can name all nine choirs of angels — let alone in order of hierarchy.
An ancient source on angels, Celestial Hierarchy, is from St. Dionysius the Areopagite or "Pseudo-Dionysius." Some believe he was St. Paul's disciple mentioned in Acts 17:34 and the first bishop of Athens, whose feast day is Oct. 3.
Seventh-century Father and Doctor of the Church St. John Damascene cited "Dionysius the Areopagite" on the nine choirs of angels' being divided "into three groups" or hierarchies. Pope St. Gregory the Great drew upon this source in the previous century, as did subsequent Doctors of the Church — like St. Bonaventure in the 13th century.
The 13th-century Angelic Doctor, St. Thomas Aquinas, in his Summa Theologiae, tapped this authoritative work when discussing the nine choirs forming three ranks:
Dionysius (Coel. Hier. vii), places in the highest hierarchy the "seraphim" as the first, the "cherubim" as the middle, the "thrones" as the last; in the middle hierarchy, he places the "dominations" as the first, the "virtues" in the middle, the "powers" last; in the lowest hierarchy the "principalities" first, then the "archangels" and, lastly, the "angels" (P. 1, Q. 108, A. 6, s.c.).
All nine choirs are in the Bible, as St. Thomas, in his Summa, shows:
For the name "seraphim" is found in Isaiah 6:2; the name "cherubim" in Ezekiel 10:15, 20; "thrones" in Colossians 1:16; "dominations," "virtues," "powers" and "principalities" are mentioned in Ephesians 1:21; the name "archangels" in the canonical epistle of St. Jude and the name "angels" is found in many places of Scripture (P. 1, Q. 108, A. 5, s.c.).
The highest rank, composed of seraphim, cherubim and thrones, "meditate upon the Person, wisdom and judgment of God." The middle rank, made of dominions, powers and virtues, "govern the forces of nature and the universe as a whole." The lowest rank is comprised of principalities, who guard "nations and cities," archangels, who guard "special people" and angels, who are "guardians and messengers to us all."
Get to know more about your heavenly companion in season one of Church Militant's Premium show Armor of God—Angels and the Immaterial World.