Greek philosopher whose thinking was primarily oriented toward logic and the sciences. He spent a good part of his intellectual life in writing critical works on Aristotle. As a student, he worked closely with Proclus and, later in life, was appointed the head of the Alexandrian school. His major commentaries, on the Categoriae and Analytica priora of Aristotle's Organon, were well-respected down to the time of the Renaissance. He also wrote on some of the physical treatises of Aristotle.