The term dualism is the state of being dual (or having a twofold division). Dualism doctrines consists of two basic opposing elements. Generally it consists of any system which is founded on a double principle.

The term dualism has several uses:

Table of contents
1 Theological usage ("Western"/"theistic")
2 Theological usage ("Eastern"/"mystic")
3 Usage in philosophy of mind
4 Usage in philosophy of science
5 Usage in physics

Theological usage ("Western"/"theistic")

Main Article: Theology

In theology, dualism can refer to the belief that there are two basic principles in the universe, usually personified as gods, that work in opposition to each other (such as good and evil). One god is good, the other evil; some religions hold that one god works for order, the other for chaos. Both the Zoroastrian religion, three millennia old and still extant, and the essentially dead gnostic (and its variations such as, Manichaeism, Bogomils, Catharism, etc.) religions are dualistic, as is Mandaeanism. The third-century Christian heretic Marcion of Sinope held that the Old and New Testaments were the work of two opposing gods.

Theological usage ("Eastern"/"mystic")

Main Article: Mysticism

Alternatively, dualism can mean the tendency of humans to perceive and understand the world as being chunked into just two categories. In this sense, it is dualistic when one perceives a tree as a thing separate from everything surrounding it, or when one perceives a "self" that is distinct from the rest of the world. In traditions such as Zen, a key to enlightenment is overcoming this sort of dualism. This is notoriously difficult, and may require a lifetime of practice.

Usage in philosophy of mind

Main Article: Mind dualism

In philosophy of mind, dualism is any of a narrow variety of views about the relationship between mind and matter, which are seen as totally different kinds of things. This type of dualism is sometimes referred to as "mind and body". This is in contrast to monism, which views mind and matter as being ultimately the same kind of thing.

Usage in philosophy of science

Main Article: The problem of other minds

In philosophy of science, dualism often refers to the dichotomy between the "subject" (the observer) and the "object" (the observed). Some critics of Western science see this kind of dualism as a fatal flaw in science. In part, this has something to do with potentially complicated interactions between the subject and the object, of the sort discussed in the social construction literature.

Usage in physics

Main Article: Duality

In physics, dualism refers to mediums with properties that can be associated with the mechanics of two different phenomena. Because these two phenomena's mechanics are mutually exclusive, both are needed in order to describe the possible behaviors.