Political epistles, or advisory court papers, form a very serious segment of Islamic intellectual heritage, especially when it comes to social thought. Such scriptures were common even before the advent of Islam, in areas where Persians ruled, and they only reappeared during the period of Seljuk rulers. The famous Seljuk vizier, Persian Nizam al-Mulk, wrote the first official political message in Islam. His epistle was called Siyasat-nama, which literally means "political epistle" - hence the new name of such prose literature. These epistles were actually books or leaflets written for rulers, and contained messages and advice on how to run the country, about social life, social justice, the relationship between religion and social life, education and care, healing, economy and many other aspects of social life. They were mostly written by viziers, advisers, ministers, but sometimes lawyers, religious authorities, philosophers, and even mystics. There are three types of political epistles. The first group consists of epistles written by viziers, advisers, and other executives within the ruling set. The basic characteristic of such epistles is their inward view of power. The second group of political epistles consists of essays in the style of today's open letters, which were left behind by prominent representatives of religious thought. Because of the normative nature of its content, this group should be clearly distinguished from scientific treatises on social sciences or other social topics. The third group of political epistles rather looks back on the past. In this group of epistles, the author does not offer a clear insight into the future, does not make specific recommendations, nor does he mention any normative values towards which rulers or their viziers should move. He merely points to the tradition of the earlier kings and sultans of the dynasty from which the ruler originated, and thus implicitly indicates what is expected of his rule. In this paper, we first seek to elucidate various features and characteristics of political epistles, in order to find out what their impact on the development of general social thought in Islam was. In order to achieve the best results, we will look more closely at the contributions of the two most significant figures in the history of political epistles. The first was Nizam al-Mulk, the famous Seljuk ruler, and the second, Rashid al-Din Fazlullah, the great vizier in the period of Ilkhanate.