ABSTRACT

Substances or 'beings' (ousiai) are, on the Aristotelian theory, the fundamental entities in the universe, the ultimate objects of natural science; and that is their role in later theories, including (with certain reservations) Locke's. Substance is also the first of the logical categories, its ontological primacy being manifested in the logical principle that other categories are predicable of substance, while substance can be predicated of nothing else. Only an individual horse can be the subject of the substantival predicate 'horse', whereas the subject of the predicate 'brown' is not an individual brown but, for example, a horse. If such an individual as this brown can indeed be identified and made the subject of predication (as in 'this brown is fading'), it exists parasitically on a substance, e.g. for just as long as this horse is brown. It is logically distinct from the substance, but exists 'in' it. So it is, in one way or another, with entities in all other categories than substance, whereas substances exist primarily and in their own right. Non-substantial things are modes of the being of substantial things.