gathered together in their new capital city of Baghdad. Contemporary also were the Syriac writers Denha (or Ibas) who compiled a commentary on the Aristotelian logical Organon: Abzud, the author of a poetical essay on the divisions of philosophy, and then, after a series of minor writers on logic, Dionysius Bar Salibi in the twelfth century A.D., who composed commentaries on the Isagoge, the Categories, Hermeneutica, and Analytica; and in the early part of the following century Yaqub Bar Shakako, author of a collection of "Dialogues" of which the second book deals with philosophical questions of logic, physics, mathematics, and metaphysics.
The series of Syriac philosophical writers closes with Gregory Bar Hebraeus, or Abu l-Faraj in the thirteenth century A.D. whose "Book of the Pupils of the Eyes" is a compendium of logic summarising and explaining the Isagoge, and Aristotle's Categories, Hermeneutica, Analytica, Topica, and Sophistica Elenchi; his "Book of the Upholding of Wisdom" being a summary introduction to logic, physics, metaphysics, and theology. A third work "The Cream of Science" is an encyclopædia of the Aristotelian philosophy, and this work appears also in an abridged form as the "Business of Businesses." He was also the translator into Syriac of Dioscorus on simples, and author of a treatise on the medical Questions of Hunayn b. Ishaq, and of a work on geography called "the Ascent of the Spirit." Although esteemed as one of the greatest Syriac authorities and for centuries holding a
