This work deals with the introductory and hermeneutic sections of a range of commentaries and studies on philosophical, scientific, biblical and other ancient authors. Special attention is given to unclearness as a stimulus for interpretation. Light is shed on the Life of an author (such as Plotinus’s) as a preliminary to the study of his works, and on the part played by the idea that life and doctrine should agree with each other. The results obtained by the study of these practices, as well as the avowed principles of ancient scholars and commentators among other things further the understanding of the interrelated philosphical, literary, medical and patristic exegetical traditions, of Galen’s autobibliographies and of Thrasyllus’s Before the Reading of the Dialogues of Plato .