This volume presents one of the first in-depth studies of Ottoman religious and intellectual history during the "dark ages" of the late 16th to 18th centuries. It endeavours to give a glimpse into the rich and multi-faceted religious and scientific interests flourishing during an era that has so far often been depicted as a period of cultural "decline". Starting from the severe criticism the Sufi preacher Fazlizade ¿Ali levelled against Istanbul's Muslims in his book "The Mirror of Hearts" which he wrote in 1740, different aspects and interpretations of Ottoman Islam are analysed: beginning with a description of Fazlizade's apocalyptic vision regarding Ottoman society, this study then focuses on discussions concerning questions of Sunni Islam such as the principles of faith, ritual duties, and ethics, on developments within Sufism and on mystic ideas that fascinated the early modern Ottoman audience. Further on, different Ottoman approaches to the use of reason and the exploration of heaven and earth are presented; and finally, the famous Ottoman poet Yusuf Nabi and his attitudes towards religion and the world at large, serve as an example for how an educated Ottoman of the late 17th century gave meaning to his life.