Doctrine of Two Principles

The foundational Stoic doctrine that the world consists of passive matter (hylē) and an active Logos, which are inseparably united with one another.

The Doctrine of Two Principles (also known as the Duality of Principles) is the metaphysical foundation of Stoic physics. It holds that all of reality is composed of two fundamental principles: passive, formless matter (hylē) and the active, shaping Logos (divine reason). These two principles are not spatially separated from one another; rather, they mutually interpenetrate. The Logos fully pervades matter, bestowing upon it structure, quality, and meaning. This doctrine was founded by Zeno and systematically elaborated by Chrysippus.