Book Delta serves as a philosophical dictionary, concluding the preliminary sections of Metaphysics. It prepares the reader for the upcoming exploration of being and substance by defining around 30 key terms. These definitions vary in length and detail, with some being extensive philosophical essays and others mere notes. The book’s aim is to clarify Aristotle’s arguments, offering a conceptual apparatus to understand discussions about being and substance.

Principle/Start: Aristotle explores different notions of “beginning” or “start.” For example, he discusses the start of a line or a process, the best starting point for production or understanding (such as starting a study not from its primary principle but from where it is easiest to begin), and the intrinsic parts from which something is primarily produced, like the keel of a ship or the foundation of a house. He notes, “That by whose choice processes and changes are initiated” as another definition of a principle or start (114).

Cause: Aristotle looks into various kinds of causes: material cause (like bronze being the cause of a statue), formal cause (the design or plan), the source of change (like a parent being the cause of a child), and the cause as an end (the purpose or final goal of an action).