Johannes Scotus Eriugena

John Scotus Eriugena, also known as Johannes Scotus Erigena, John the Scot or John the Irish-born (c. 800 – c. 877), was an Irish Neoplatonic philosopher, theologian and poet of the Early Middle Ages. Bertrand Russell dubbed him "the most astonishing person of the ninth century". The Stanford Encyclopedia of Philosophy states that 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 (physis), which John 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 (logos) of God.

Eriugena is generally classified as a Neoplatonist, though he seems to have been influenced more by the anonymous and pseudepigraphic 6th century Christian author of the Corpus Areopagitica, rather than by the work of pagan philosophers such as Plotinus or Iamblichus. Relying exclusively on Christian theology and the 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. Eriugena's predecessor, Alcuin, is well-known as the Magister recruited by Charlemagne to revive the study of the liberal arts--the trivium and quadrivium--whose transmission had fallen into a much deteriorated and low estate in the west.

He was one of the few Western European philosophers of his day who knew Greek, having studied it in Ireland. 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.