Henry Bett's Johannes Scotus Erigena: A Study in Mediaeval Philosophy, first published in 1925, presents one of the most comprehensive studies of this great Irish Neoplatonist philosopher and theologian of the Early Middle Ages. The author begins with a brief overview of Erigena's life in ninth-century Ireland before moving to an extensive exposition and summary of his writings. Particular attention is given to Erigena's greatest work, On the Division of Nature. Bett explores such ideas as the Fourfold Division of Nature, modes of non-being, and theophany, as well as Erigena's negative theology. He also addresses the notion that Erigena's perspective is pantheistic, an accusation that contributed to his works being burned by Pope Honorius III. The book concludes with an examination of Erigena's considerable influence on subsequent medieval theology and philosophy, and his continued relevance today.