John Scotus Eriugena[a] or Johannes Scotus Erigena[b] or John the Scot (c. 800 – c. 877)[3] was an Irish Catholic Neoplatonist philosopher, theologian and poet of the Early Middle Ages. Bertrand Russell dubbed him “the most astonishing person of the ninth century”. The Stanford Encyclopaedia of Philosophy states he “is the most significant Irish intellectual of the early monastic period. He is generally recognized to be both the outstanding philosopher (in terms of originality) of the Carolingian era and of the whole period of Latin philosophy stretching from Boethius to Anselm.”

He wrote a number of works, but is best known today for having written De Divisione Naturae (The Division of Nature), or Periphyseon, which has been called the “final achievement” of ancient philosophy, a work which “synthesizes the philosophical accomplishments of fifteen centuries.” The principal concern of De Divisione Naturae is to unfold from φύσις, which the Scot defines as “all things which are and which are not”, the entire integrated structure of reality. Eriugena achieves this through a dialectical method elaborated through exitus and reditus, that interweaves the structure of the human mind and reality as produced by the λόγος of God.[4]

Eriugena is generally classified as a Neoplatonist, though he was not influenced directly by such pagan philosophers as Plotinus or Iamblichus, Jean Trouillard stated that, although he was almost exclusively dependent on Christian theological texts and the Christian Canon, Eriugena, “reinvented the greater part of the theses of Neoplatonism.”

He succeeded Alcuin of York (c. 735–804) as head of the Palace School at Aachen. He also translated and made commentaries upon the work of Dionysius the Areopagite, and was one of the few Western European philosophers of his day who knew Greek, having studied in Byzantine Athens. A later medieval tradition recounts that Eriugena was stabbed to death by his students at Malmesbury with their pens, although this may rather be allegorical.[5]