 The categories used could be more or less specific, so on one side might be “human being” or “animal” while on the most general side all things could be classified as either yin or yang. Another of the most common categories were wood, earth, fire, air, and metal, known as the five phases (wuxing). Yet another set were based on the Yi Jing, using either the eight trigrams or sixty-four hexagrams. These systems of categorization were eventually integrated, so that categories from one could be translated into the others. Given the underlying ontology of change and process, categorization is not based on inherent qualities or essences but on typical ways of acting and reacting—does it tend to expand or contract, work gradually or swiftly, manifest itself obviously or subtly? Since these traits are relational, the same “thing” may not always be in the same category (it might act like wood in one context but metal in another), and because they are dynamic, the categories give immediate information on how things can be controlled, influenced, or disrupted. The application of the categories depends on context and the context depends on our particular purposes, but they are meant to express real properties of things.