Investigation the effect of duality on the ethics of Zoroastrian religion

Dualism idea is one of the most important ideas in Zoroastrianism that has put in the centrality of cosmology in this religion. This idea has attempted to describe and divide the World into two origins namely good and evil that contrast with each other. Dualism is an idea that has anticipated to be presented in all levels and structures of this religion like system of morality. In this paper, we have attempted to survey the influence of this idea on the system of morality in Zoroastrianism by adopting two approaches: Textbased approach and logical approach. In Text- based approach, we have regarded to survey of similarities and coexistences in the Text, between Dualism and concepts of morality. By adopting of this approach, we can perceive this idea has left its dichotomy among the concepts of morality in different ways and has oriented toward itself. Because a discussion about the lack of relation between descriptive and morality propositions always challenges the relationship between moral principles and cosmology of a religion، this topic has been regarded as a second approach in order to survey the issue in this paper. In this approach, we have considered the logical relation between the concepts of morality and Dualism as an idea that attempts to describe the World in a special method. In one hand, if we consider the influence as a deduction of cosmology propositions and in the other hand, the logical relation has not been existed between (ought and is), on the basis of this, any kind of relation and assumption of the influence between cosmology of Dualism and morality on the behalf of authors of these Texts and Founders has considered, it has been on the basis of logical fault and sophistry (is and ought). Although with comprehensive look on the historical process of Zoroastrian ethics، we can find out the deep influence of dualism on morality principles in Pahlavi literature unto Old Avesta that has been reduced and we can see a kind of movement toward the severing of the ethics from cosmology principles.