The book reconstructs the theological concepts shared by the Theban monks for the first time based on documentary sources. It gleans scattered evidence from hundreds of private letters preserved on ostraca and, in several cases, papyri. Such documents do not expound on complex theological systems but use particular phrases, words and images loaded with religious meaning. These snapshots represent microtheologies - particular, fragmented realizations of the complex religious system. The book focuses on monastic status, use of the Bible, prayer and blessing, invocations of God and saints. etc. It also presents a big picture of a pessimistic worldview in which a human being is weak and constantly endangered, and God is the only one possessing the knowledge and means to rescue him from the vicissitudes of life. The book will be of interest to papyrologists, historians of late antiquity, historians of religion and theologians.