 The Categories divides naturally into three distinct parts — what have come to be known as the Pre-Predicamenta (chs.1–4), the Predicamenta (chs. 5–9), and the Post-Predicamenta (chs. 10-15). (These section titles reflect the traditional Latin title of the entire work, the Predicamenta.) In the Pre-Predicamenta, Aristotle discusses a number of semantic relations (1a1–16), gives a division of beings (τἃ ὄντα), into four kinds (1a20–1b9), and then presents his canonical list of ten categories (1b25–2a4). In the Predicamenta, Aristotle discusses in detail the categories of substance (2a12–4b19), quantity (4b20–6a36), relatives (6a37–8b24), and quality (8b25–11a39), and provides a cursory treatment of the other categories (11b1–14). And finally, in the Post-Predicamenta, he discusses a number of concepts relating to modes of opposition (11b15–14A25), priority and simultaneity (14a26–15a13), motion (15a14–15b17), and ends with a brief discussion of having (15b18–31). There is considerable debate about whether Aristotle thought all three parts belong to a single work, and if he did, why he thought they are all needed for the work to be a unified whole. There is nonetheless widespread agreement that at the very heart of the Categories are two systems of classification, one given in the Pre-Predicamenta, and the other in the Predicamenta.