Introduction: ʻAbd al-Ghanī and the culture of correspondence -- The intellectual milieu -- The letters of the Wasā'il -- List and description -- Places, towns, and correspondents -- Map of the Eastern Ottoman Provinces -- Content and significance -- On understanding Islam: letter 1 -- On struggle (jihād): letter 3 -- On causality: letter 4 -- On solitude: letters 6 and 10 -- On quick-passing thoughts (khawāṭir): letter 14 -- On smoking: letter 25 -- On cosmogony and the unity of being: letters 61 and 62 -- On piety, spirituality, and ethics: all letters