In Christianity, angels are agents of God, based on angels in Judaism. The most influential Christian angelic hierarchy was that put forward by Pseudo-Dionysius the Areopagite in the 4th or 5th century in his book De Coelesti Hierarchia (On the Celestial Hierarchy).
During the Middle Ages, many schemes were proposed about the hierarchy of angels, some drawing on and expanding on Pseudo-Dionysius, others suggesting completely different classifications.
Pseudo-Dionysius (On the Celestial Hierarchy) and Thomas Aquinas (Summa Theologica) drew on passages from the New Testament, specifically in Galatians 3:26-28, Matthew 22:24-33, Ephesians 1:21-23, and Colossians 1:16, to develop a schema of three Hierarchies, Spheres or Triads of angels, with each Hierarchy containing three Orders or Choirs. Although both authors drew on the New Testament, the Biblical canon is unclear on the subject, and these hierarchies are considered less definitive than biblical material.
As referred to in the theological doctrine of the communion of saints, in Paradise there is a common and unique vision of the truth and contemplation of the Face of God, without any kind of difference between angels or human souls. The Summa theologiae states that there exist different degree in respect of the creation, about the power of intercession to God and of direct entrustment in the human lives.
The first sphere angels serve as the heavenly servants of God the Son incarnated.
Seraphim (singular "Seraph") are, literally translated, "burning ones". The word seraph is normally a synonym for serpents when used in the Hebrew Bible. Mentioned in Isaiah 6:1–7, Seraphim are the highest angelic class and they serve as the caretakers of God's throne and continuously shout praises: "Holy, holy, holy is the Lord of hosts; the whole earth is full of His glory!" According to Isaiah 6:1–8, the Seraphim are described as fiery six-winged beings; with two wings that cover their faces, with another two that cover their feet, and the last two they use to fly.
Cherubim have four faces: one of a man, an ox, a lion, and an eagle (later adopted as the symbols of the four evangelists). They have four conjoined wings covered with eyes (although Revelation 4:8 appears to describe them with six wings like the seraphim), a lion's body, and the feet of oxen. Cherubim guard the way to the tree of life in the Garden of Eden (Genesis 3:24) and the throne of God (Ezekiel 28:14–16).
Modern English usage has blurred the distinction between cherubim and putti. Putti are the often wingless (sometimes winged) human baby/toddler-like beings traditionally used in figurative art.
The "Thrones" (Greek: thronoi, pl. of thronos), or Elders, are a class of celestial beings mentioned by Paul the Apostle in Colossians 1:16 (New Testament). They are living symbols of God's justice and authority, and have as one of their symbols the throne.
It is not unusual to find that the Thrones are associated, by some, with the Ophanim or Erelim from the Jewish angelic hierarchy. The idea that they are separate or one in the same is debated. The Ophanim or Ofanim, also called galgalim, refer to the wheels seen in Ezekiel's vision of the chariot in Ezekiel 1:15-21. One of the Dead Sea scrolls construes them as angels, late sections of the Book of Enoch portray them as a class of celestial beings who never sleep, but guard the throne of God. The Ophanim (Heb. ofanim: Wheels, from the vision of Daniel 7:9) are unusual looking, even compared with the other celestial beings. They are closely connected with the Cherubim: "When they moved, the others moved; when they stopped, the others stopped; and when they rose from the earth, the wheels rose along with them; for the spirit of the living creatures [Cherubim] was in the wheels." Ezekiel 10:17 NRSV. Which raises the question of if they are angels at all or controlled by the Cherubim.
Some Christian theologians that include the Thrones as one of the choirs do not describe them as wheels, describing them as adoring elder men who listen to the will of God and present the prayers of men. The Twenty-Four Elders in the Book of Revelation are usually thought to be part of this group of angels.
Angels of the Second Sphere work as heavenly governors of the creation by subjecting matter and guiding and ruling the spirits.
Dominions or Lordships
The "Dominions" (Eph. 1:21; Col. 1:16) (lat. dominatio, plural dominationes, also translated from the Greek term kyriotētes, pl. of kyriotēs, as "Lordships") or "Dominations" are presented as the hierarchy of celestial beings "Lordships" in some English translations of the De Coelesti Hierarchia. The Dominions regulate the duties of lower angels. It is only with extreme rarity that the angelic lords make themselves physically known to humans.
The Dominions are believed to look like divinely beautiful humans with a pair of feathered wings, much like the common representation of angels, but they may be distinguished from other groups by wielding orbs of light fastened to the heads of their scepters or on the pommel of their swords.
Virtues or Strongholds
These angels are those through which signs and miracles are made in the world.
The term appears to be linked to the attribute "might", from the Greek root dynamis (pl. dynameis) in Ephesians 1:21, which is also translated as "Virtue" or "Power". They are presented as the celestial Choir "Virtues", in the Summa Theologica.
"The name of the holy Virtues signifies a certain powerful and unshakable virility welling forth into all their Godlike energies; not being weak and feeble for any reception of the divine Illuminations granted to it; mounting upwards in fullness of power to an assimilation with God; never falling away from the Divine Life through its own weakness, but ascending unwaveringly to the superessential Virtue which is the Source of virtue: fashioning itself, as far as it may, in virtue; perfectly turned towards the Source of virtue, and flowing forth providentially to those below it, abundantly filling them with virtue."
Powers or Authorities
The "Powers" (lat. potestas (f), pl. potestates), or "Authorities", from the Greek exousiai, pl. of exousia (see Greek root in Eph 3:10). The primary duty of the "Powers" is to supervise the movements of the heavenly bodies to ensure that the cosmos remains in order. Being warrior angels, they also oppose evil spirits, especially those that make use of the matter in the universe, and often cast evil spirits to places of detention. These angels are usually represented as soldiers wearing full armor and helmet, and also having defensive and offensive weapons such as shields and spears or chains respectively.
Angels who function as heavenly guides, protectors, and messengers to human beings.
Principalities or Rulers
The "Principalities" (Latin: principatus) also translated as "Princedoms" and "Rulers", from the Greek archai, pl. of archē (see Greek root in Eph 3:10), are the angels that guide and protect nations, or groups of peoples, and institutions such as the Church. The Principalities preside over the bands of angels and charge them with fulfilling the divine ministry. There are some who administer and some who assist.
The Principalities are shown wearing a crown and carrying a sceptre. Their duty also is said to be to carry out the orders given to them by the upper sphere angels and bequeath blessings to the material world. Their task is to oversee groups of people. They are the educators and guardians of the realm of earth. Like beings related to the world of the germinal ideas, they are said to inspire living things to many things such as art or science.
The word "archangel" comes from the Greek ἀρχάγγελος (archangelos), meaning chief angel, a translation of the Hebrew רַב־מַלְאָך (rav-mal'ákh) It derives from the Greek archein, meaning to be first in rank or power; and angelos which means messenger or envoy. The word is only used twice in the New Testament: 1 Thessalonians 4:16 and Jude 1:9. Only Michael and Gabriel are mentioned by name in the New Testament.
In most Christian traditions Gabriel is also considered an archangel, but there is no direct literary support for this assumption. It is also worth noting that the term "archangel" appears only in the singular, never plural, and only in specific reference to Michael. 
The name of the archangel Raphael appears only in the Book of Tobit (Tobias). Tobit is considered deuterocanonical by Catholics (both Eastern and Western Rites), Eastern Orthodox Christians, and Anglicans. The Book of Tobit is not, however, acknowledged by most Protestant denominations, such as Reformed Christians or Baptists. Raphael said to Tobias that he was "one of the seven who stand before the Lord", and it is generally believed that Michael and Gabriel are two of the other six.
A fourth Archangel is Uriel whose name literally means "Light of God." Uriel's name is the only one not mentioned in the Western Christian Bible, but plays a prominent role in an apocryphon read by Anglican and Russian Orthodox Christians: The second Book of Esdras (fourth Books of Esdras in the Latin Vulgate). In the book, he unveils seven prophecies to the prophet Ezra, after whom the book is named. He also plays a role in the apocryphal Book of Enoch, which is considered canonical by the Ethiopian Orthodox, Eritrean Orthodox, and Ethiopian Catholic Churches. The Catholic Church generally does not regard Uriel as an angel just as the Book of Enoch is not part of the Catholic Bible used by most Catholics either.
Another possible interpretation of the seven archangels is that these seven are the seven spirits of God that stand before the throne described in the Book of Enoch, and in the Book of Revelation.
The Seven Archangels are said to be the guardian angels of nations and countries, and are concerned with the issues and events surrounding these, including politics, military matters, commerce and trade: e.g. Archangel Michael is traditionally seen as the protector of 'Israel' and of the ecclesia (Gr. root ekklesia from the New Testament passages), theologically equated as the Church, the forerunner of the spiritual New Israel.
Some[who?] make a distinction between archangel (with a lower-case a) and Archangel (with an uppercase A). The former can denote the second-lowest choir (arch-angels in the sense of being just above the lowest Choir of angels that is called only "angels") but the latter may denote the highest of all the angels (i.e., Arch-angels in the sense of being above all angels, of any Choir. The seven highest Seraphim, Michael, being the highest of all).
The "angels" or malakhim (Heb.: מַלְאָכִים), i.e. the "plain" angels (Gr.: ἄγγελοι, pl. of Gr.: ἄγγελος, angelos, i.e. messenger or envoy), are the lowest order of celestial beings, and the most recognized. They are the ones most concerned with the affairs of men. Within the category of the angels, there are many different kinds, with different functions. The angels are sent as messengers to humanity. Personal guardian angels come from this class.
Personal guardian angels
Personal guardian angels are not of a separate order, but rather come from the order of Angels. It is a common belief that they are assigned to every human being, Christian or not. It is unknown whether they guard multiple humans during their existence or just one, but the latter is a more typical opinion.
Choirs in medieval theology
During the Middle Ages, many schemes were proposed, some drawing on and expanding on Pseudo-Dionysius, others suggesting completely different classifications (some authors limited the number of Choirs to seven). Several other hierarchies were proposed, some in nearly inverted order. Some of those schemes are here presented:
- Apostolic Constitutions (4th century):
- 1. Seraphim, 2. Cherubim, 3. Aeons, 4. Hosts, 5. Powers (=Virtues, Greek dynameis), 6. Authorities, 7. Principalities, 8. Dominions, 9. Thrones, 10. Archangels, 11. Angels.
- St. Ambrose in Apologia Prophet David, 5 (4th century):
- 1. Seraphim, 2. Cherubim, 3. Dominations, 4. Thrones, 5. Principalities, 6. Potentates (or Powers), 7. Virtues, 8. Archangels, 9. Angels.
- St. Jerome (4th century):
- 1. Seraphim, 2. Cherubim, 3. Powers, 4. Dominions (Dominations), 5. Thrones, 6. Archangels, 7. Angels.
- Pseudo-Dionysius the Areopagite in De Coelesti Hierarchia (ca. 5th century):
- First sphere: 1. Seraphim, 2. Cherubim, 3. Thrones;
- Second sphere: 4. Dominations (also translated as Lordships), 5. Virtues (also trans. as Powers), 6. Powers (also trans. as Authorities);
- Third sphere: 7. Principalities, 8. Archangels, 9. Angels.
- St. Gregory the Great in Homilia (6th century)
- 1. Seraphim, 2. Cherubim, 3. Thrones, 4. Dominations, 5. Principalities, 6. Powers, 7. Virtues, 8. Archangels, 9. Angels.
- St. Isidore of Seville in Etymologiae (7th century):
- 1. Seraphim, 2. Cherubim, 3. Thrones, 4. Dominations, 5. Principalities, 6. Powers, 7. Virtues, 8. Archangels, 9. Angels.
- John of Damascus in De Fide Orthodoxa (8th century):
- 1. Seraphim, 2. Cherubim, 3. Thrones, 4. Dominions, 5. Powers (=Virtues), 6. Authorities, 7. Rulers (=Principalities), 8. Archangels, 9. Angels.
- St. Hildegard of Bingen in Scivias  (1098–1179):
- 1. Seraphim, Cherubim;
- 2. Thrones, Dominations, Principalities, Powers and Virtues;
- 3. Archangels and Angels.
- St. Thomas Aquinas in Summa Theologica (1225–1274):
- 1. Seraphim, Cherubim, and Thrones;
- 2. Dominations, Virtues, and Powers;
- 3. Principalities, Archangels, and Angels.
- Dante Alighieri in The Divine Comedy (1308–1321)
- 1. Seraphim, 2. Cherubim, 3. Thrones, 4. Dominations, 5. Virtues, 6. Powers, 7. Principalities, 8. Archangels, 9. Angels.
Individual angels and demons from the choirs
- Seraphim: In John Milton's Paradise Lost Satan and the Archangels belong to this choir ("archangel" has here the meaning of "most powerful angel", not the members of the second lowest choir). Beelzebuth is also addressed as prince of the seraphim in witchcraft litanies.
- Cherubim: In Paradise Lost, Beelzebub and Azazel were cherubim before their fall. St. Thomas Aquinas in Summa Theologica states that Satan belongs to this choir, not to the seraphim.
- Thrones: Paradise Lost cites the demons Adramelec and Asmodai. Some sources mention Astaroth as well.
- Virtues: Witchcraft litanies mention Belial.
- Archangels: The archangels Gabriel, Raphael and Michael, and supposedly the other archangels as well, are usually assigned to this choir, for example in the hierarchies of St. Gregory and St. Isidore of Seville.
- Classification of demons
- Christian demonology
- Dynamics of the celestial spheres
- Fallen angel
- Heavenly host
- Hierarchy of angels
- Islamic angelic hierarchy
- Jewish angelic hierarchy
- Ye Watchers and Ye Holy Ones
- Zoroastrian angelic hierarchy
- Barker, Margaret (2004). An Extraordinary Gathering of Angels, M Q Publications.
- Chase, Steven (2002). Angelic spirituality. p. 264. ISBN 978-0-8091-3948-4.
- McInerny, Ralph M. (1998). Selected writings of Thomas Aquinas. p. 841. ISBN 978-0-14-043632-7.
- "Strong's H8314 - Saraph". Blue Letter Bible. Retrieved 2015-04-01.
- "Genesis 3 - NET Bible". Bible.org. Retrieved 2007-03-13.
- "Ezekiel 10 - NET Bible". Bible.org. Retrieved 2008-11-10.
- "Ezekiel 10 - NET Bible". Bible.org. Retrieved 2007-03-13.
- "1 Kings 6 - NET Bible". Bible.org. Retrieved 2007-03-13.
- "SUMMA THEOLOGICA: The malice of the angels with regard to sin (Prima Pars, Q. 63)". Newadvent.org. Retrieved 2011-12-05.
- Isidore of Seville: Etymologies
- "Dionysius the Areopagite: Celestial Hierarchy". Esoteric.msu.edu. Retrieved 2011-12-05.
- King James Bible "Authorized Version", (Cambridge ed.). Cambridge Edition. pp. Ephesian 6:10.
- "NET BibleŽ - Ephesians 1". Bible.org. Retrieved 2011-12-05.
- "NET BibleŽ - Ephesians 3". Bible.org. Retrieved 2011-12-05.
- Strong, J, Strong's Exhaustive Concordance of the Bible, Riverside Books and Bible House, Iowa Falls (Iowa), ISBN 0-917006-01-1.
- The Hope of the Apostolic Church: Or, the Duties and Privileges of Christians in Connexion with the Second Advent, as Unfolded in the First Epistle to the Thessalonians. J. Nisbet & Son. 1845. p. 130.
- Jude 1:9
- Vatican bans rogue angels. Telegraph.co.uk. Retrieved 2019-01-03.
- Why the book of enoch is not included in the bible. Archived 2018-11-06 at the Wayback Machine Catholic.com. Retrieved 2019-01-03.
- Revelation 1:5.
- "CATHOLIC ENCYCLOPEDIA: Guardian Angels". www.newadvent.org. Retrieved 2016-03-05.
- Online, Catholic. "Who are our Guardian Angels? - Angels - Saints & Angels - Catholic Online". www.catholic.org. Retrieved 2016-03-05.
- Mother Columba Hart, Bishop, Jane, Newman Barbara (1990) Hildegard of Bingen: Scivias (Classics of Western Spirituality) U.S.A.:Paulist Press. Vision Six, page 139f. Amazon.com
- Jules Garinet: Historie de la Magie en France (1818)
- Sebastian Michaelis: The Admirable History of the Possession and Conversion of a Penitent Woman
- Barker, Margaret. An Extraordinary Gathering of Angels. M Q Publications, 2004.
- Copeland, Mark. Ministering Spirits: Angels In The Old Testament. Executable Outlines. 2004.
- Copeland, Mark. Terms And Descriptions Of Angels. Executable Outlines. 2004.
- Fares, Aymen. Angelics and the Angelic Realm. Spiritual.com.au Pty. Ltd. 2000.
- Tatum, Johnny. The Hierarchy of Angels: Hierarchical Chart of Angels. Worldnet Grace Ministries.
- Tatum, Johnny. The Hierarchy of Angels: Distinguishing the Higher Ranked. Worldnet Grace Ministries.
- The Bible (Searchable online version)
- Pseudo-Dionysus the Areopagite. The Celestial Hierarchy.