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.
Dual economy
Dual economies are common in less developed countries, where one sector is geared to local needs and another to the global export market. Dual economies may exist within the same sector, for example a modern plantation or other commercial agricultural entity operating in the midst of traditional cropping systems. Sir Arthur Lewis used the concept of a dualistic economy as the basis of his labour supply theory of rural-urban migration. Lewis distinguished between a rural low-income subsistence sector with surplus population, and an expanding urban capitalist sector (see Dual-sector model). The urban economy absorbed labour from rural areas (holding down urban wages) until the rural surplus was exhausted.