Active principle
Pneuma
In Stoicism, the concept of the passive principle refers to the material aspect of the universe, which is acted upon or shaped by the active principle. These two principles together explain the functioning and existence of everything in the cosmos.
The active principle is the rational, formative force that organizes and gives shape to the passive principle. This active principle is often identified with Logos – the divine reason), God, or the cosmic rationality that permeates and orders the universe. It is responsible for the order, structure, and life in the cosmos, infusing the passive matter with purpose and direction.
The passive principle in Stoicism refers to the raw material or matter of the universe, which is shaped and ordered by the active principle, the rational and formative force that gives structure and purpose to everything. Together, these two principles explain the Stoic understanding of the physical and metaphysical nature of the world.