Polytheists regard the world to be neutral, both clean and dirty. Polytheist author Kenaz Filan explains, “The world is a clean flowing stream, and miasma the sewage dumped into the water. We clean the stream by filtering that sewage or by redirecting it…to where it can be properly contained.” (Note 1, Note 2)
In the official theology of Christianity, evil is the absence of good. For a person to be evil, they have to choose to disobey God. Meanwhile, Manicheanism divides the Cosmos into Spirit and Matter, Good and Evil, Light and Darkness. The two are equal and opposing powers. Evil has agency and purpose to overtake Good.
Christianity considers Manicheanism to be a heresy. However, because of Augustine who was a Manichaean before converting, some of its heretical doctrines have become embedded in Christian thought. Augustine stated that world was both corrupt and corrupting. And, in the minds of many Christians, evil has to be fought or it will overcome the good.
The duality of Manicheanism has carried over to Polytheism via Christianity. For example, the Norse God Loki does not conform to Christian morality. He becomes problematic for Heathens who still carry the Protestant world view. They will not invoke Loki at blots, since they regard Him to be evil.
Note 1. The Romans have a Goddess – Lua – who protects all things purified by rituals and for rituals.
Note 2. Kenez Filan, “Miasma” from “With Clean Minds and Clean Hands,” Galina Krasskova, ed. p. 69.
Adkins, Lesley and Roy Adkins, “Dictionary of Roman Religion.” New York: Oxford University Press. 1996.
Jones, Kile, “A Comparison between Manichean and Christian Views of Evil.” Meta Religion. Web: http://www.meta-religion.com/Philosophy/Articles/Other/Mani_paper.htm
Kirsch, Jonathan, “A History of the End of the World.” New York: HarperCollins. 2006.
“God Against the Gods.” New York: Penguin Books. 2004
Krasskova, Galina, “Devotional Polytheism.” Sanngetall Press. 2014.
“With Clean Minds and Clean Hands.” Sanngetall Press. 2017.
Samples, Kevin, “Exploring Manichaeism: St. Augustine, Part 3.” Reasons to Believe. 26 June 2012. Web: http://www.reasons.org/blogs/reflections/exploring-manichaeism-st.-augustine-part-3