Zoroastrianism in antiquity was fundamentally dualist, built on the idea that the world is composed in equal parts of two types of creation, some by the benevolent god Ohrmazd, which were to be cultivated, and others by the wicked Ahriman, to be eliminated. A short thread. 1/8

The most basic requirement of Zoroastrian cosmology was to maintain the good creations and eliminate the inversely corresponded bad creations. For instance, every good animal, like a dog, had a wicked counterpart, like a wolf. Wicked animals were called Xrafstar. 2

Herodotus already knows about this when he says: "The Magi kill with their own hands every creature, except dogs and men; they kill all alike, ants and snakes, creeping and flying things, and take great pride in it." 3

Zoroastrian sources themselves indicate that it was a positive obligation to kill bad animals (Xrafstar). The Pahlavi Videvdad (18.2) even includes a "xrafstaragan," or xrafstar-killer, among the implements that a priest might wear and use. 4

Plutarch reports: [Persians] believe that some plants belong to the good god & others to the evil daemon; also of animals they think that dogs, fowls,& hedgehogs..belong to the good god, but that water-rats belong to the evil one..the man who has killed the most [is] fortunate. 5

In his Convivial Questions, the banquet participants conclude on the basis of Zoroastrianism that reverence for animals is manifested by protecting them, hatred by killing them; since Jews do not slaughter pigs, the participants conclude that they therefore must revere them... 6

Acc. to Agathias, Zoroastrians had a "festival of the slaying of the evil ones" in which "they kill huge numbers of reptiles & other wild creatures..& present them to the magi as a proof of their devotion..an agreeable service to the good divinity..thwarting & injuring Ahriman" 7

Zoroastrian cosmology was so much more than a numerical belief in two battling divine beings and their creations; it was an all encompassing system of thought and practice that stirred Zoroastrians to constantly consider whether they were aiding Ohrmazd or abetting Ahriman. 8/fin