Dualism

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Dualism is any account of reality built on two ultimate principles that cannot be reduced to one another — spirit and matter, light and darkness, good and evil, mind and body. The word is modern, coined in the eighteenth century, but the structure it names is ancient and recurs in religion and philosophy alike. What unites its many forms is a refusal: the conviction that the divided world cannot be traced back to a single source without leaving something essential unexplained.

It is worth separating two kinds that the single word tends to blur. There is cosmic or ethical dualism, which sets two opposed powers at the foundation of existence and reads the world as their battlefield; and there is the dualism of philosophy of mind, which holds that thinking substance and extended matter are two distinct kinds of thing. The first is a claim about the order of the cosmos, the second a claim about the make-up of a person, and they answer different questions.

The cosmic form has the longer history. Zoroastrian tradition set the wise lord Ahura Mazda against a hostile spirit and made the whole of time a contest between them. The currents later grouped as Gnostic taught that the material world was the work of a lesser, ignorant maker, and that a spark of the true divine lay trapped within it — a picture in which matter is not merely lower than spirit but alien to it. Manichaeism, founded by the prophet Mani in third-century Persia, pressed this furthest into a thoroughgoing system of two eternal realms, Light and Darkness, intermixed in the present age and destined to be separated again. How far these systems were genuinely dual, and how far that charge was sharpened by their opponents, is contested; much of what was long known of the Gnostics came from heresiologists writing to refute them.

Strict monotheism and Platonism both resisted this turn. For thinkers in the Neoplatonic line, evil and matter are not a rival principle but a privation, a falling-away from the One that remains the single source of everything; Plotinus devoted a tractate to attacking the Gnostics on just this point. The argument is old and unsettled: whether the world’s evident division demands two roots, or whether one source can be reconciled with a fractured world.

The mind-body form belongs to a later debate. The sharpest statement is associated with Descartes in the seventeenth century, who distinguished thinking substance from extended substance so cleanly that their interaction became a standing problem — how an immaterial mind moves a material body, and how the body’s states reach the mind. That difficulty has driven much of the philosophy of mind since, and the various monisms that followed were largely attempts to escape it.

To call a system dualist is often less a neutral description than the judgment of a rival who held the world to be one. The label tends to be applied from outside, by those for whom unity was the thing to defend.

→ In the library: Mead — Fragments of a Faith Forgotten (1900) · Plotinus — Against the Gnostics (Enneads II.9, MacKenna 1926)

→ Related: Gnosis · Neoplatonism · Cartesianism · Aeon · Emanation