The commentary attributed to Simplicius on Aristotle's On the Soul appears in this series in three volumes, of which this is the first. The translation provides the first opportunity for a wider readership to assess the disputed question of authorship. Is the work by Simplicius, or by his colleague Priscian, or by another commentator? In the second volume, Priscian's Paraphrase of Theophrastus on Sense Perception, which covers the same subject, will also be translated for comparison. Whatever its authorship, the commentary is a major source for late Neoplatonist theories of thought and sense perception and provides considerable insight into this important area of Aristotle's thought. In this first volume, the Neoplatonist commentator covers the first half of Aristotle's On the Soul, comprising Aristotle's survey of his predecessors and his own rival account of the nature of the soul.