Johannes Scotus Erigena (ca. 810–ca. 877), commonly known as Eriugena, was an Irish monk, translator, and philosopher. By 851, he was at the West Frankish court of Charles the Bald, where he would remain for the rest of his life at the palace school. His Periphyseon has been called the “final achievement” of ancient philosophy and draws on Eriugena’s knowledge of both the Greek and Latin Christian theological traditions, remarkable in the Carolingian world. The work presents a Neoplatonic cosmology in the form of a catechetical dialogue between master and pupil covering the fourfold division of nature, in which all of reality is involved in a procession from and return to the One.
Although Eriugena had followers in his time and later among the mystics—the School of St. Victor, Eckhart, Tauler, Ruysbroeck, and the German mystics, and Nicholas of Cusa and his professed disciple Giordano Bruno—many in the West did not welcome his ideas, and his work was condemned by Honorius III in 1225.