Ennead VI.4–5, originally written as a single treatise, contains Plotinus’ most general and sustained exposition of the relationship between the intelligible and sensible realms, addressing and coalescing two central issues in Platonism: the nature of the soul–body relationship and the nature of participation. Its main question is, How can soul animate bodies without sharing in their extension? The treatise seems to have had considerable impact: it is much reflected in Porphyry’s important work, Sententiae, and the doctrine of reception according to the capacity of the recipient, for which this treatise is the main source, resonated in medieval thinkers.

Plotinus was a Platonist, committed to expounding the doctrines put forward by Plato some seven centuries earlier. He was born and educated in Egypt, where he studied the teachings of Plato under the guidance of Ammonius Saccas. He came to Rome in 244 CE and built up a circle of followers devoted to studying Plato through Plato's own works and those of philosophers, both Platonist and non-Platonist, of the intervening centuries. From his fiftieth year Plotinus himself wrote down, in Greek, the findings of the seminars, and these writings were later edited by one of his pupils, Porphyry, and published in six groups of nine treatises entitled the Enneads (from the Greek word for nine – ennea).