Introduction of Marcus Aurelius’ meditations by Gregory Hayes page xxi But the logos is not simply an impersonal power that governs and directs the world. It is also an actual substance that provides that world, not in metaphorical sense, but in a form as concrete as oxygen or carbon. In its physical embodiment, the logos exists as pneuma, a substance imagined by the earliest Stoics as pure fire, and by Chrysippus as a mixture of fire and air. Pneuma is the power -the vital breath-that animates animals and humans. It is, and Dylan Thomas‘s phrase, ”the force that through the green fuse drives the flower,” and is present even in…