A famous Neoplatonic Christian mystic from the early Middle Ages, Pseudo-Disonysius the Areopagite wrote a tract called [[Celestial Hierarchies]] which described the [[Angels]] which populate the orders of heaven. This text is one of the founding texts of the [[Via Negativa]] in Christian mysticism, and influenced virtually all Christian mystics who came after him. [[Meister Eckhart]] was influenced by him.