Ideas spread and evolve like genes—through variation, selection, and replication. Richard Dawkins coined "memes" to describe units of cultural information that propagate from mind to mind. Understanding memetic evolution explains how cultures change, why some ideas spread while others die, and how to design messages that stick.

Social institutions like parliaments, currencies, and corporations are simultaneously as real as mountains and as fragile as collective dreams. They exist only because we collectively agree they exist, yet this shared belief makes them powerfully real in shaping behavior and organizing society. When enough people stop believing, these seemingly permanent structures can crumble overnight—think of the Soviet Union dissolving or a currency collapsing.