Monism, dualism and nondualism

Monism holds that reality is ultimately one, one substance, one principle, or one kind of thing. Its instances include Advaita Vedanta, for which only Brahman is finally real; Spinoza, for whom there is a single substance with infinite attributes, called God or Nature; Stoic cosmology, with its one rational principle pervading everything; and, in an entirely different register, the materialist monism that holds everything to be one kind of stuff.

Dualism holds that there are two irreducible principles, and the word covers several quite different claims whose conflation is the standard error in this area. Metaphysical dualism of good and evil, in Zoroastrianism and more radically in Manichaeism, posits two opposed cosmic powers; it is the position that most cleanly solves the problem of evil, at the cost of divine omnipotence, which is precisely why the monotheisms rejected it so firmly. Samkhya's dualism of purusha and prakriti divides consciousness from everything else and has nothing to do with good and evil. Cartesian dualism of mind and body divides thinking substance from extended substance and generates the interaction problem that has occupied philosophy of mind ever since. These three have almost nothing in common beyond the number two.

Nondualism, advaita, is the position that most needs distinguishing from monism, and its adherents insist on the distinction. Advaita means "not two" rather than "one", and the negative formulation is deliberate: to assert that all is one is still to make a positive claim about a totality, and still to count. Advaita Vedanta holds that the apparent duality of self and Brahman is not real, without thereby asserting a monistic substance in the way Western monism does. Much of Mahayana Buddhism, and Madhyamaka especially, is nondual in a stronger sense still, refusing "one" and "two" and every other position, since emptiness is not a thing that everything turns out to be. Kashmir Shaivism, Dzogchen and the Sufi wahdat al-wujud are generally placed here as well.

The distinctions matter practically, because a different path follows from each. If reality is one substance, knowledge of it is the aim. If there are two irreducible principles, discriminating between them is the aim, which is exactly what Samkhya prescribes. If duality is an appearance, then neither uniting nor separating is required, but only the ending of a misperception, which is why Advaita makes knowledge rather than action the means.

Western scholarship's long habit of translating advaita as "monism" has been criticised at length by scholars of Indian philosophy on precisely this ground, and the criticism is a good illustration of how much a translation choice can decide in comparative work before any argument begins.

Most of this cluster of positions is philosophical rather than disciplinary, argued over rather than ruled on. Metaphysical dualism of good and evil is the exception, because more than one church body has formally condemned it rather than merely disagreed with it.

Manichaeism, teaching two eternal principles of light and darkness locked in cosmic struggle, was condemned repeatedly by the early church, and Augustine's own decade as a Manichaean hearer before his conversion gave Western Christian anti-dualism its most influential critic from the inside. Centuries later, Catharism, a medieval dualist movement strongest in southern France, taught a comparable division between a good spiritual God and an evil material creator, and it was suppressed rather than merely refuted: the Albigensian Crusade from 1209 and the Fourth Lateran Council's 1215 canons directed against heresy together ended it as an organised movement in the West.

The reason given, then and since, is usually the problem it appears to solve too easily. Dualism accounts for evil without compromising a good God's power, but only by dividing sovereignty itself, and the monotheistic traditions have consistently judged that price too high, preferring accounts of evil that leave omnipotence and goodness both intact even at the cost of a harder philosophical problem. Zoroastrianism, by contrast, built its cosmology on the division rather than treating it as an error to be excluded, and never faced an equivalent internal suppression for holding it.