Neo-Platonists

The Theological and Philosophical Works of Hermes Trismegistus, Christian Neo-Platonist. Translation, preface, and annotations by John David Chambers (Edinburgh, 1882 reissued Ann Arbor, 1967, and New York, 1975). 

Hovering behind these four elements was a shadowy and iU-defincd fifth. Aristotle called it ether, the element of the stars the neo Platonists called it Logos, otherwise the Word, God, or Reason and among the medieval philosophers it was known as the quinta essencia fifth being, or quintessence, sometime confused in alchemy with the Philosopher s Stone,... 

---