The article discusses the problem of the formation of philosophical prose in the Persian language. The first section presents a brief excursion into the history of philosophical prose in Persian and the stages of formation of modern Persian as a language of science and philosophy. In the Arab-Muslim philosophical tradition, representatives of various schools and trends contributed to the development of philosophical terminology in Farsi. The author dwells on the works of such philosophers as Ibn Sīnā, Nāṣir Khusraw, Naṣīr al-Dīn al-Ṭūsī, Aḥmad al-Ghazālī, ʼAbū Ḥāmid al-Ghazālī and gives an overview of their works written in Persian. The second section poses the question whether the Persian language proved able to compete with the Arabic language in the field of science. The author examines the style of philosophical prose in Farsi, considering the causes of creation of Persian-language philosophical texts and defining their target audience. The article presents viewpoints of modern orientalist researchers as well as the views of medieval philosophers who wrote in Persian. We find that most philosophical texts in Persian were written for a public who had little or no knowledge of the Arabic language, yet wanted to get acquainted with current philosophical and religious doctrines, albeit in an abbreviated format. The conclusion summarizes and presents two positions regarding the necessity of writing philosophical prose in Persian. According to one point of view, Persian-language philosophical works helped people who did not speak Arabic to get acquainted with the concepts and views of contemporary philosophy. According to an alternative view, there was no special need to compose philosophical texts in Persian, because the corpus of Arabic philosophical terminology had already been formed, and these Arabic terms were widely and successfully used, while the new Persian philosophical vocabulary was difficult to understand.