The fame of the Jacobite Christian Abu Zakariyya Yahya ibn 'Adi (893 bis 974) as in influential philosopher and as en eminent apologist of the Christian faith has been founded on reputation rather than on the study of his work. When Augustin Perier compiled the first list of his writings in 1920, most of his philosophical works were believed to be lost. Most recent publications have enabled us to appraise his merits as a translator an commentator of Aristotle. But only a few of his philosophical monographs were available until an important collection of his treatises was discovered inthe libraries of Tehran. This. at last, has enabled us to study in detail his contribution to logic, his treatment of physical and metaphysical problems, and his position on questions of Muslim "kalam." The Monophysite theology of Yahya ibn 'Adi, on the other hand, though better known through the studies of G Graf and A. Perier, still awaits renewed examination. The most important works in this field have not even been published. So the new inventory of his writings is intended to provide the basis for a reassessment of his merits as an Aristotelean as well as a Christian thinker.The study contains a survey of biographical data, detailed bibliographical information on manuscripts and printed works and summaries of most the unpublished texts. The fame of the Jacobite Christian Abu Zakariyya Yahya ibn 'Adi (893 bis 974) as in influential philosopher and as en eminent apologist of the Christian faith has been founded on reputation rather than on the study of his work. When Augustin Perier compiled the first list of his writings in 1920, most of his philosophical works were believed to be lost. Most recent publications have enabled us to appraise his merits as a translator an commentator of Aristotle. But only a few of his philosophical monographs were available until an important collection of his treatises was discovered inthe libraries of Tehran. This. at last, has enabled us to study in detail his contribution to logic, his treatment of physical and metaphysical problems, and his position on questions of Muslim "kalam." The Monophysite theology of Yahya ibn 'Adi, on the other hand, though better known through the studies of G Graf and A. Perier, still awaits renewed examination. The most important works in this field have not even been published. So the new inventory of his writings is intended to provide the basis for a reassessment of his merits as an Aristotelean as well as a Christian thinker.The study contains a survey of biographical data, detailed bibliographical information on manuscripts and printed works and summaries of most the unpublished texts. The fame of the Jacobite Christian Abu Zakariyya Yahya ibn 'Adi (893-974) as in influential philosopher and as en eminent apologist of the Christian faith has been founded on reputation rather than on the study of his work. When Augustin Perier compiled the first list of his writings in 1920, most of his philosophical works were believed to be lost. Most recent publications have enabled us to appraise his merits as a translator an commentator of Aristotle. But only a few of his philosophical monographs were available until an important collection of his treatises was discovered inthe libraries of Tehran. This. at last, has enabled us to study in detail his contribution to logic, his treatment of physical and metaphysical problems, and his position on questions of Muslim "kalam." The Monophysite theology of Yahya ibn 'Adi, on the other hand, though better known through the studies of G Graf and A. Perier, still awaits renewed examination. The most important works in this field have not even been published. So the new inventory of his writings is intended to provide the basis for a reassessment of his merits as an Aristotelean as well as a Christian thinker.The study contains a survey of biographical data, detailed bibliographical information on manuscripts and printed works and summaries of most the unpublished texts.