This qualitative research aims to explore and unravel the theory of natural law within its Greek context and its influence on political thought, particularly addressing the need to counteract the damages of tyranny and the cyclical succession of regimes, as articulated by Plato. This study reveals that the concept of natural law predates Stoics and it is rooted within the pre-Socratic natural philosophy. The study exposes that Aristotelian ethics and politics are rooted in the concept of natural law, ultimately giving (...) rise to the Aristotelian "mixed form of government" and laying the groundwork for republicanism. In extending this inquiry, I attempt to identify a parallel argument in ancient Iran, investigating the presence of natural law and its impact on the political landscape. The concept of natural law, emphasizing the alignment of social and political affairs with nature's rules, played a significant role in shaping the Indo-Iranian communities. The Sanskrit term rta and its Avestan equivalent, Aša, denote this foundational concept. However, the ascendancy of Zoroastrianism and its new theology led to the consolidation of all Indo-Iranian gods into the singular omnipotent deity, Ahura Mazdā. Ahura Mazdā, along with its prophet Zaraθuštra, possessed the authority to govern both earthly life and the afterlife. The exclusive attributes of Ahu and Ratu empowered God and its messenger to formulate and enact laws ensuring a place in heaven. Consequently, Divine Law and positive law became intricately intertwined within a unified legal framework. This divine law, sanctioned by God and enforced by the King, diverges from the Greek perspective, particularly that of Aristotle, where tyranny is seen as a deviation from the ideal political order. In the Iranian context, tyranny is synonymous with God's representation, sharing the holiness and regal attributes of a King, who, in the Iranian and Avestan sense, enjoys God's blessing as Xvarənah or Faer-e Izadi. The intertwining of law and authority of the King precludes the possibility of an independent legal sovereignty apart from the King’s authority. The monotheistic tenets of Zaraθuštra’s religion, officially established in the 4th century AD as the Religion of the State, solidify this integrated system. Consequently, the coexistence of republicanism or any mixed form of government within Iran becomes unattainable under the influence of this monotheistic doctrine. (shrink)