 This way of thinking about God is made especially clear in the longer treatise on the Trinity (I). When God is said to have an attribute, how is this predication to be understood? For created things, on the Aristotelian scheme, a predication is either substantial (when the genus, species or differentia is predicated of something: ‘Socrates is an animal/man/rational’) or accidental, when the predicate is any accident in any of the nine Aristotelian categories of accident. Augustine had already acknowledged that nothing is predicated of God accidentally. Predications about him may be relative, as when he is called ‘Father’ or ‘Son’, or substantial. Even when a quality or quantity is attributed to him, the predication is substantial. When we say of a created thing that it is great or good, we are affirming that it participates in greatness or goodness: it is one thing for the thing to exist, another for it to be great or good. But God is greatness itself and goodness itself, and so, when we say, ‘God is good’ or ‘God is great’, we are not affirming any attribute of him beyond what he is as a substance. This Augustinian view is faithfully set out in the brief Treatise II.