Henology

Henology (from hen, “one”) is the study of the One as first principle — as opposed to ontology, the study of being. Because the Neoplatonists placed the One beyond being, they held it cannot be captured by the categories that apply to existing things; the One is approached only by negation, and at last by a union beyond thought.

The term is modern, but the project is Plotinus’ and Proclus’: to give an account of that which grounds all accounts. It marks the deepest difference between the Platonic tradition and an Aristotelian metaphysics that makes being itself the highest study.