Angelic Hierarchy
Angelic Hierarchy according to St. Thomas Aquinas:
Seraphim
Cherubim
Thrones
Dominions
Virtues
Powers
Principalities
Archangels
Angels
In the (Summa Theologiae I-I q55, a3), in treating of the angelic knowledge, the superior angels have a more universal knowledge of the truth than the inferior angels. This universal knowledge has three grades among the angels.
St. Thomas made intelligence the basis of the classification of the angels, who are themselves purely intellectual beings. The angels do not all have the same degree of likeness to the Lord, however; some participate in or reflect the divine perfections more than others. Therefore, according to the Angelic Doctor, angels belong to different choirs according to their intelligence and their place in God’s plan.
Thus does St. Thomas speak of the three-fold division of the angelic hierarchy into three hierarchies, each with three choirs of angels.
The highest group of angels — the seraphim, the cherubim, and the thrones — not only contemplate God directly but are totally concerned with Him. In Him, they contemplate the source of all creation, the ultimate ideas and causes from which all creation flows. In other words, they contemplate God in His highest perfections
The second level, or sphere, of the angels — the dominations, the virtues, and the powers — do not possess the same kind of unified vision as the higher choirs. They see reality divided into the fundamental causes from which all things stem.
And then the third group — the principalities, the archangels, and the angels — have a further devolved understanding of the truth of the universe, from the large and basic causes of all things into a multiplicity of particular causes. Finally, the lowest hierarchy (Principalities, Archangels and Angels) understands the knowledge communicated from the higher choirs as it relates to particular realities and serves to effect in creation the will of God, such as the laws of nature, and the guardianship of societies and individuals.