De Coelesti Hierarchia
De Coelesti Hierarchia (Greek: Περὶ τῆς Οὐρανίας Ἱεραρχίας, "On the Celestial Hierarchy") is a Pseudo-Dionysian work on angelology, written in Greek and dated to ca. the 5th century CE; it exerted great influence on scholasticism and treats at great length the hierarchies of angels.
The work has also been very influential in the development of Eastern Orthodox Church theology.
Thomas Aquinas (Summa Theologica, I.108) follows the Hierarchia (6.7) in dividing the angels into three hierarchies each of which contains three orders, based on their proximity to God, corresponding to the nine orders of angels recognized by Pope Gregory I.
- The Celestial Hierarchy – full text translated into English (1899)
- The Celestial Hierarchy (original Ancient Greek text)