John Scotus 'Eriugena' (Irish-born) was the supreme philosopher of the Carolingian world. Brought from Ireland by King Charles the Bald around 845 as master of the palace school at Laon, he was the only thinker of his century with full command of Greek.
At Charles's commission he translated into Latin the entire corpus of Pseudo-Dionysius the Areopagite — the four great Greek treatises on mystical theology that became foundational to medieval Latin contemplative tradition — and the works of Maximus the Confessor. Through his translation Pseudo-Dionysius reached Western theologians from Hugh of St. Victor to Aquinas to John of the Cross.
His own great philosophical synthesis, Periphyseon ('On the Division of Nature,' c. 867), is the most ambitious Latin metaphysical work between Augustine and Aquinas — though the Council of Sens (1225) condemned portions of it for pantheistic tendencies. His translations escaped condemnation.
Tradition holds he ended his days at Malmesbury Abbey in England, perhaps invited by King Alfred. His later medieval cult was local and unofficial — he is honored as a Blessed but never formally canonized.