Syrian scholar and author of a noted collection of annotations on the entire Syriac Bible. The work is also an important historical and theological source on Eastern religious sects during the first millennium of Christianity.

A native of Kaškar, Iraq, Theodore was probably a monk in the Nestorian Christian church, a heretical group adhering to the teachings of the 5th-century theologian Nestorius, who emphasized the human personhood of Christ while attenuating his divinity. Theodore's only extant work is the Liber scholiorum (“Book of Annotations”), the Latin designation of a vast Syriac collection of observations and elucidations taking their point of departure from biblical passages but developed into detailed considerations of philosophy, psychology, logic, and Eastern religions. Containing 11 mēmrē, or general sections of commentary, the work includes apologetic texts disputing non-Christian religions, particularly Islām and Manichaeism, an Oriental dualistic sect positing an evil deity responsible for the origins of the material world. The Syriac text of the Liber scholiorum was edited with Latin notes by Addaï Scher in the series Corpus scriptorum Christianorum Orientalium (“Corpus of Eastern Christian Writers”), vol. 65–66 (1912).