There were lots of great author along the history of Persian Language who inherited different kinds of works. From 4th Hegira up to nowadays that lots of prose texts has been composed there are few, if any, subjects in philosophical, theological, mystical, literary and scientific that we cannot find some book(s) about. There are some information in the introduction section of these books about author and its contemporaries, general information about the work itself and so on; moreover, there would be some information about the necessity of the work composition that would explain and justify its goals and composition reason in a brief and comprehensive manner. The main question in the current study is that what is the real reason of composition of these works in their authors' view? Authors have gained some piece of data after reviewing 150 works from the most famous Persian prose works in different subjects and genres and divided them into different categories. The general result is that most of these works were written due to the order or request of someone and few, if any, works have been written due to the author's own decision and motive. This issue has often been rooted in personal, social, economic and even political reasons that this article tries to deal with and shed light on its causes.