Final answer:
Evil according to the Manicheans is a material substance, reflecting their dualistic belief that the physical world is inherently evil, as opposed to the spiritual realm of good.
Step-by-step explanation:
According to the Manicheans, evil is considered to be a material substance. The Manichean belief posits that the physical world, and hence matter, is the realm of evil, which exists in opposition to the spiritual realm of good. This dualistic religion founded by the prophet Mani in the 3rd century AD sees the universe as a battleground between these opposing forces, where humans and their souls are caught in the middle.
The concept of evil in different philosophical and religious traditions varies greatly. For example, in the Judeo-Christian tradition, evil is typically understood as a result of human free will and disobedience, as seen in the story of the Fall in the Garden of Eden, described by St. Augustine. Alternatively, the philosopher Leibniz suggested that what we perceive as 'evil' is actually part of a greater good in the best of all possible worlds, and is therefore a necessary feature of a perfect creation.
In contrast to these perspectives, the Free Will Defense postulates that the deity is not responsible for evil; rather, individuals are responsible for choosing evil of their own accord, since they possess and make choices using free will.