Philo's Quod deterius is a discussion of the Cain and Abel episode in the Bible. Philo follows the Greek translation of the Septuagint, not the Hebrew text, although he may have known traditions that relied on the Hebrew. His treatment of the text is unique, combining elements of traditional Greek commentary on literary texts, moralizing diatribe in highly wrought rhetorical language, midrashic-like exegesis involving the extensive use of other biblical passages, and philosophical theory. The present commentary illuminates these various components of Philo's discussion, especially by means of parallel texts, pagan, Jewish, and Christian, from across antiquity. Using these sources and paying attention to ancient exegetical thinking, Adam Kamesar attempts to trace the overall direction and coherence of what Philo is saying. This kind of treatment of Philo's allegorical treatises has rarely been undertaken before on this scale. The volume also includes a new English translation of the work.