This classic publication provides evidence about the transmission of Greek philosophy to the Arabs through Syriac: the fragments of the Syriac translation of Ptolemy's life of Aristotle (which contains Aristotle's will), and the Syriac commentaries Porphyry's Isagoge; this life of Aristotle was the sole source on Aristotle known to the Arabs. Baumstark's copious introduction summarizes the life and works of the translator, Ptolemy el Gebir, whom Baumstark identifies with the slightly less obscure mythographer and grammarian Ptolemy Chennos, the differences between the two surviving summaries of the Syriac translation, and their reflections in Arabic writing about Aristotle; his intricate theories about the transmission of the variants between the two texts deserve reconsideration in the original. The phrasing in Arabic reflects Syriac rather than Greek, as with the commentaries on Porphyry by John Philoponus, Stephen of Alexandria, and two unknown authors; the Syriac affected Arabic philosophical terminology. Much of the Syriac text is translated in the process of analysis.