This book presents a critical overview of contemporary research on the life of the Neoplatonist philisopher Simplicius and on three of his five commentaries (on the Encheiridion of Epictetus, Aristotle's De anima, and Aristotle's Categories). The first part of the work brings out the historical role of Simplicius, who was originally from the province of Cilicia in Asia Minor, studied in Alexandria and Athens, and - so the evidence suggests - spent the last years of his life as head of a philosophical school specialized in mathematics in Syria, close to the Persian frontier. His role in the history of thought is as an intermediary between Greco-Roman philosophy and philosophy in the Syriac language, which in turn became an important source for the beginnings of Arabic philosophy. The second part of the book is devoted to questions of doctrine and authenticity; its goal is to reveal the educational programme and methods used by the Neoplatonist commentators, which are too often neglected by modern interpreters.