  In the first kind of predication, the predicate expresses what a subject is. For example, in ‘Socrates is a man,’ ‘man’ indicates that Socrates is a man. Of course, one can ask further what man is, and so on until one reaches the highest term, which is substance. The same is true, mutatis mutandis, of any other individual subject, for all subjects are in the end some kind of primary substance, of which everything else is predicated. This kind of predication accounts for the first and most basic category, substance [substantia].