Manichaean doctrine is premised on a material and ethical dualism. The known cosmos is a mixture of two antithetical realms of being, originally separate and eternally incompatible. The realm of light is a wholly good, harmonious universe in which God, the father of greatness, dwells with innumerable light beings, which are one with him in substance and character. The realm of darkness is a wholly evil, chaotic universe dominated by a king of darkness and his female counterpart. At the beginning of time, the realm of darkness perceives and covets the realm of light and attacks it, unaware of the harm that contact with it will bring to itself. The prescient father of greatness fends off this aggression by putting forth a series of emanations to act out a strategy of containment and ultimate reseparation of light and darkness. In the primordial battle, one of these emanations enters into mixture with darkness, constraining it and forestalling a breach of the boundaries of the realm of light. This mythological background explains the evident condition of the known cosmos, in which everything is a mixture of conflicted substances and forces, engaged in a perpetual struggle for mastery. The point of Manichaean instruction is learning to identify oneself with the forces of light and goodness and striving for their ultimate reseparation from entanglement with darkness and evil.
Manichaeism is closer to Zoroastrian dualism than to Gnostic or Platonic varieties in that it avoids a spirit-matter dichotomy. Both light and darkness have material as well as spiritual properties, and even the most subtle forces are usually treated in materialistic terms. Manichaeism also shares with Zoroastrianism an activist mythology and ethic, rejecting the notion of a sinful "fall" of the soul in favor of the idea of a voluntaristic "leap" of the soul in the service of God's purposes. In other details, Manichaeism has greater affinity to Indian thinking, for example in seeing souls not only in human beings, but in all living things, even in rocks and dirt. For the Manichaeans, the soul is a collective entity, a consubstantial emanation of the deity, broken up into individuals only temporarily through mixture with evil. Humans are only one small part of a universal process of struggle and liberation of the world soul. This world soul carries with it all positive properties, such as life, growth, beauty, and brightness, whereas evil contributes to the mixture only death, decay, ugliness, and gloom. Whereas for Zoroastrians the goal is to expel evil from this world, the Manichaeans see this world as unperfectable, a temporary scene of conflict and suffering from which ultimate escape is envisioned. In this respect, Manichaeism has a common outlook with Buddhism and Jainism, as well as the more eschatological and ascetic strains of Christianity.
Based on these ideas, Manichaean practice entailed a rigorous behavioral code, designed to avoid harming the world soul in all things as much as possible, as well as ritual practices intended to aid the process of its liberation. Outbursts of anger, impatience, stupidity, greed, hatred, and violence attest to the mixture of evil with good in the human body. The evil elements must be identified for what they are, repented, resisted, and ultimately overcome by the Manichaean. Due to a number of adventitious factors, individuals have different capacities for this task, and consequently the community is divided into two grades. The first, that of the elect, was made up of those men and women willing and able to take on the most vigorous form of self-discipline, involving celibacy, poverty, and a wandering life preaching the faith. These had the ability to transmute material elements within their bodies, freeing soul fragments from the food brought to them, as well as the potential to achieve liberation at death. Those unable to adopt this life were called auditors, who remained engaged in hearth and home, but supported the elect while striving for advancement in the faith through moral growth and a better rebirth.