Moral dualism is the belief in two opposing forces in conflict. The most common dualism in moral discourse is good versus evil, but there are others. Dualism is common in pre-Islamic Persian belief systems, especially Persia's native religion, Zoroastrianism. Dualism contrasts with Western religious systems such as Christianity and Islam, which affirm the existence of evil but insist that God is good, in charge and will ultimately triumph.

Dualism in Religion

In religion, dualism is any system of religious beliefs that explains the universe in terms of two opposing forces. The key concept in labeling a religion dualistic is the notion of two uncreated forces that use the universe as a battleground. In monistic religions like Christianity, only God is eternal and uncreated, and everything in the universe stems from Him. In addition, a dualistic system explains human evil using a force from without, whereas religions like Christianity believe the problem lies within humanity.

Common Dualisms

The most well-known dualism is good versus evil. In dualistic systems this can theoretically be two deities, but the more common dualism is a good God versus an evil -- yet uncreated and eternal -- entity. Gnostic dualistic systems stress matter versus spirit, with matter being the evil realm and spirit being the good realm. This was reflected in many Christian-inspired Gnostic sects in the early days of the church, which contrasted the good God of Jesus against the creator God of the Old Testament. Light versus dark is another common duality.

The Legacy of Zoroastrianism in Persia

Zoroastrianism, founded by Zoroaster about 3,500 years ago in Persia, was a significant force in Persia until the Muslim conquest of the Seventh Century. Hartford Seminary's Encyclopedia of Religion and Society credits Zoroastrianism for the "Judeo-Christian idea of the Devil," which makes Persia a critical place in the formation of Western religion. Zoroastrianism is still recognized in modern-day Iran as one of four official religions.

Dualism in Zoroastrianism

Zoroastrianism is both monotheistic and dualistic. It shares the monotheism of Judaism, Christianity and Islam, and Zoroastrians believe the One God is the creator of the universe. At the same time, there is another force that created death and evil. The world is understood as a struggle between these two forces. Zoroastrians believe good will triumph over evil.

Dualism in Manichaeism

Manichaeism is also a dualistic religion of Persian lineage. The religion comes from modern-day Iraq but its founder, Mani, was a Persian. Manichaeism is usually described as a fusion of all the religious systems available at the time, featuring elements of Christianity, Buddhism and Gnosticism. Manichaeism preached a duality of good and spirit versus evil and matter, and Jesus was cast as "the light of the world" in another dualism -- light versus dark.