The debate on vernacular literacy in seventeenth-century Ottoman Empire During the seventeenth century vernacular literacy gained a greater visibility in the Ottoman world of letters. One manifestation of this development was the proliferation of texts that were written expressly for a lay readership, including among them catechisms (ilmihal) and books of advice (nasihatnames, pendnames, etc.) In several such texts, the writers also discussed whom they considered “literate” and whom “illiterate” as well as what they made of those urban folk who could read only in the Turkish vernacular or who aspired to learn Persian without having first mastered Arabic and the religiolegal learning transmitted in that language. Through a contextualized study of these texts, this paper explores how the growing importance of lay readership informed Ottoman understandings of “literacy,” and “illiteracy” and elicited a new debate about the value of vernacular literacy. It is argued that the distinctions Ottoman literati made between the “lettered” (‘alim) and the “unlettered” (ümmi) reflected not just differences in literacy skills but also religious and social anxieties provoked by the emergence of a new reading public that was socially more diverse and distinctively more “urbane” (?ehri) in its ethos. This paper is structured in three parts. In the first part, we shall look specifically at a hitherto overlooked catechism, the Mebhas-? ?man written by a little-known sufi and scholar, Nushi en-Nasihi ca. 1633. This text offers a particularly extended discussion of elementary instruction and lay literacy in early seventeenth-century Ottoman Empire. It also offers some novel views on how best to guide the lay public through the written medium. In the second part of this paper, we shall expand our scope to take stock of similar views expressed by other seventeenth-century literati such as Abdülmecit Sivasi, Katip Çelebi and Mehmed Nazmi. In the concluding section, we shall offer some views about how the growing importance of lay readership and the elite responses to it also informed the so-called sufi-Kad?zadeli controversy about “innovations” (bid‘at), which unravelled during the same period.