The terminology Aristotle uses in Metaphysics has played a role in the development of philosophical vocabulary. Aristotle claims that the investigation of being amounts to the investigation of substance. Interestingly, only the central books of Metaphysics—Zeta, Eta, and Theta—address substance as the main theme. The contents of Beta, Gamma, Epsilon, Theta, Lambda, Mu, and Nu supplement this discussion in various ways by addressing more or less loosely related topics. In Metaphysics book Zeta, Aristotle develops a hylomorphic theory. Aristotle's surviving works remain notoriously difficult to read. In Metaphysics, he uses highly technical, jargon-filled language and presents his very complex ideas in terse, dense prose. Metaphysics also lacks continuous and coherent narrative-another reason readers find it difficult to understand. "Much of the technical vocabulary of later philosophy is derived from Latin versions of Aristotle's metaphysical terms: for example, 'substance', 'essence', 'quality', 'quantity' and 'category"'.