Three ways of answering “how many?”
When religions ask what ultimately exists, the answers tend to be one, two or “not two”. The number is shorthand for a position about reality. This article sorts those positions and gives examples of each. It treats them as doctrines held by communities, with arguments and internal disagreements, and not as statements about a mystical meaning of the numeral.
The focus here is the contrast between dualistic and non-dual thinking.
Kinds of dualism
The word “dualism” covers several different ideas, and mixing them causes confusion.
- Cosmic or moral dualism: two opposed forces, usually good and evil, contend in the world.
- Metaphysical dualism: two basic kinds of thing exist, such as mind and matter, or spirit and body.
- Dualism of God and creation: a creator is distinct from the world. Many monotheistic religions affirm this without being dualist in the first sense, because they hold that there is one ultimate God.
A tradition can hold one of these without the others, which is why labels like “dualistic religion” need to be used with care.
Zoroastrian good and evil
Zoroastrianism, the ancient Iranian religion, is the classic case of a moral dualism. Its oldest hymns present a choice between truth and falsehood, and later tradition personifies the opposition as the good god Ahura Mazda and a hostile spirit, Angra Mainyu. The world is a battleground, human beings are asked to take the side of good through their conduct, and the tradition expects a final renewal of the world in which evil is defeated.
Two points matter for comparison. First, the dualism is ethical and cosmic: it is about the struggle between good and evil, rather than a division between spirit and matter, and the physical world is generally seen as good. Second, scholars note that Zoroastrian texts and interpretations differ over how equal the two powers are, and over whether the good god is ultimately supreme. The Amesha Spentas, the divine helpers of Ahura Mazda, show that this is not a simple matter of two opposing camps.
Manichaeism, a later religion founded in the third century CE, is often presented as a stricter dualism of light and darkness in which spirit is mixed with matter and must be released. It spread widely but did not survive as a major religion.
Dualism of spirit and matter in Indian thought
Dualism is not only a Western or Iranian topic. The Samkhya school of Indian philosophy, one of the classical schools, describes reality as made of two principles: purusha, conscious awareness, and prakriti, the material and mental stuff of nature. Liberation, in Samkhya, comes through discriminating between the two. This is a metaphysical dualism, and it is notable that it contains no struggle between good and evil.
Some devotional schools of Vedanta, including Dvaita (the “dualist” school associated with the medieval teacher Madhva), hold that the individual soul and God are eternally distinct. Here the “two” refers to the relationship between creature and creator.
Non-dual traditions
Against these stand traditions that reject ultimate division.
Advaita Vedanta. The name means “not two”. Teachers in this school, most associated with Shankara (traditionally placed in the eighth century CE), taught that the true self, atman, and the ultimate reality, Brahman, are not different, and that the appearance of multiplicity arises from ignorance. In this view, duality is a way things appear, not the final truth.
Madhyamaka Buddhism. Nagarjuna’s school argued that opposed categories such as existence and non-existence, or self and other, both fail to describe things as they are. The path between them is called the middle way. The related concept of emptiness is discussed under zero as emptiness, though emptiness in Buddhism is a doctrine about dependent existence, not a theory of numbers.
Taoism. Often described as complementary rather than strictly non-dual, Taoist thought treats paired opposites as arising together and interpenetrating, as in yin and yang. It differs from Zoroastrian dualism because the two sides are not at war.
Monotheism and the question of evil
Monotheistic traditions faced a related puzzle: if one good God made everything, where does evil come from? Different answers developed, including freedom of will, the idea that evil is a lack or privation of good, and the existence of fallen spiritual beings. Some Christian discussions of the Trinity doctrine also show how a tradition can speak of one God in a structure of three, which is a different kind of numerical language again.
Mainstream Jewish, Christian and Islamic thought generally rejected a full dualism of two equal powers, which is part of why late antique movements that taught one were criticised by their opponents.
What the comparison shows
Two can mean opposition, complement, distinction or illusion, depending on the system. A moral dualism like Zoroastrianism gives human choices cosmic weight. A metaphysical dualism like Samkhya separates awareness from nature. Non-dual traditions argue that the separation is not ultimately real. These are different answers to different questions, and the number itself is the same in all of them, which is why it is the doctrine and not the digit that deserves study.