In the 860s John Scottus Eriugena wrote the Periphyseon (later entitled De divisione naturae, that is, “On the Division of Nature”).

The Periphyseon is a long work, filling nearly six hundred columns of the Patrologia Latina volume and containing approximately 217,450 words, written in the form of an extended dialogue between two anonymous philosophers who are known only as Nutritor and Alumnus or, in the twelfth-century manuscript edited by William of Malmesbury, as “M” (Magister) and “D” (Discipulus). The work is divided into five books, and in some later manuscripts these books are divided into chapters, though this was never completely achieved.

Little is known about the occasion and circumstances which gave rise to the composition of the Periphyseon. Roughly, it has been dated as written between 860 and 866. As the dialogue contains many quotations and excerpts from Greek authors, including Dionysius and Maximus, and it is known that Eriugena did not begin translating Dionysius until 860, it is postulated that he began the work in the early 860s. In his critical edition, Sheldon-Williams contends that the work developed from an earlier book on logic or dialectic, a De dialectica. It is indeed true that Eriugena's contemporaries saw the work in this light, especially as the chief philosophical work of the day was the Categoriae decem, but there is no other evidence to support Sheldon-Williams's claim, and in fact his analysis seems to distort the structure of Book I of the Periphyseon.