Dualistic cosmology
Moral dualism is the belief of the great complement of, or conflict between, the benevolent and the malevolent. It simply implies that there are two moral opposites at work, independent of any interpretation of what might be "moral" and independent of how these may be represented. Moral opposites might, for example, exist in a worldview which has one god, more than one god, or none. By contrast, duotheism, bitheism or ditheism implies (at least) two gods. While bitheism implies harmony, ditheism implies rivalry and opposition, such as between good and evil, or light and dark, or summer and winter. For example, a ditheistic system could be one in which one god is a creator, and the other a destroyer. In theology, dualism can also refer to the relationship between the deity and creation or the deity and the universe (see theistic dualism). This form of dualism is a belief shared in certain traditions of Christianity and Hinduism. Alternatively, in ontological dualism, the world is divided into two overarching categories. The opposition and combination of the universe's two basic principles of yin and yang is a large part of Chinese philosophy, and is an important feature of Taoism. It is also discussed in Confucianism.
Plato's unwritten doctrines
According to the prevailing view of researchers today, although the two principles are considered elements of a finally monistic system, they also have a dualistic aspect. This is not contested by defenders of the monistic interpretation but they assert the dualistic aspect is subordinated to a totality that is monistic. Its dualistic nature remains because not only the One but also the Indefinite Dyad is treated as a fundamental principle. Giovanni Reale emphasized the role of the Dyad as a fundamental origin. He thought, however, that the concept of dualism was inappropriate and spoke of a 'bipolar structure of reality.' For him, however, these two 'poles' were not equally significant: the One 'remains hierarchically superior to the Dyad.' Heinz Happ, Marie-Dominique Richard, and Paul Wilpert argued against every derivation of the Dyad from a superior principle of unity, and consequently contended that Plato's system was dualistic. They believe that Plato's originally dualistic system was later reinterpreted as a kind of monism.