Abstract

Drawing upon John Burnet’s interpretation of mesotēs, I explore the original meanings of this important Greek word and its inherent relations to the conceptsof formal cause, final cause, and actuality (energeia). My investigation reveals the concept of mesotēs as an Ariadne’s thread running through the whole system ofAristotle’s moral and natural philosophy. It also throws a new light on the implications of Aristotle’s definition of moral virtue and the essential role it plays in the truth of human existence.