Dualism in cosmology is the moral or spiritual belief that two fundamental concepts exist, which often oppose each other. It is an umbrella term that covers a diversity of views from various spiritual and religious beliefs, including both traditional religions and scriptural religions.
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.
Many myths and creation motifs with dualistic cosmologies have been described in ethnographic and anthropological literature. These motifs conceive the world as being created, organized, or influenced by two demiurges, culture heroes, or other mythological beings, who either compete with each other or have a complementary function in creating, arranging or influencing the world. There is a huge diversity of such cosmologies. In some cases, such as among the Chukchi, the beings collaborate rather than competing and contribute to the creation in a coequal way. In many other instances the two beings are not of the same importance or power (sometimes, one of them is even characterized as gullible). Sometimes they can be contrasted as good versus evil. They may often be believed to be twins or at least brothers. Dualistic motifs in mythologies can be observed on all inhabited continents.
Gnosticism is a diverse, syncretistic religious movement consisting of various belief systems generally united in the teaching that humans are divine souls trapped in a material world created by an imperfect god, the demiurge. The demiurge may be depicted as an embodiment of evil, or in other instances as merely imperfect and as benevolent as its inadequacy permits. This demiurge exists alongside another remote and unknowable supreme being that embodies good or God.
Bogomils, Paulicians and Cathars are typically seen as being imitative of Gnosticism. Whether or not the Cathari possessed direct historical influence from ancient Gnosticism is a matter of dispute. The basic conceptions of Gnostic cosmology are, however, to be found in Cathar beliefs (most distinctly in their notion of a lesser creator god). Unlike the second century Gnostics, they did not apparently place any special relevance upon knowledge (gnosis) as an effective salvific force. 
Although most Left Hand Path occultists and atheists are told that Baphomet is nothing more than a symbolic representation of the Universal synthesis of polarities, the alchemical process unifying light and dark that occurs during the Magnum Opus or spiritual Ascension, this innocuous depiction is a grossly inaccurate deception. It is accurate to say that in the co-existence of light and darkness, life and the death passage are ultimately two sides of the same spiritual coin that are inseparable from each other in this matter realm. However, this basic awareness of the Natural Laws that include the cosmological understanding of Dualism, the Law of Polarity, as represented in the Baphomet Deception, is precariously incomplete without the comprehension that humanity is also actively enduring a consciousness war involving intruding groups.