Definition
Dualism is the religious worldview that holds two equal, opposing principles — typically good and evil, light and dark — as co-eternal forces. Neither created the other; neither will fully defeat the other within ordinary time. The dualist universe is a battlefield, and human beings are conscripts on one side or the other.
Zoroastrianism is the canonical example: the wise lord Ahura Mazda and the destructive Angra Mainyu are locked in a struggle that will end only at the cosmic finale. Gnosticism, Manichaeism, and Cathar Christianity carry variants of the same structure into the Mediterranean and European worlds.
Why it matters
How it works
A dualist religion divides the cosmos into two domains and assigns every event, choice, and entity to one side. Disease, drought, and oppression flow from the dark principle; healing, harvest, and justice flow from the light. Salvation is enlistment: align with the good force, refuse the evil one, and contribute to a victory that, while not in doubt, is still pending.
Harari highlights how this two-force schema is psychologically satisfying — it explains evil without blaming the god you worship — and how it tends to leak into nominally monotheistic traditions through their angelology and demonology.