Many primary schools, however, remain open.
Thus, everything in the category of substance that is not itself a primary substance is, ultimately, 'said of' primary substances.
How many primary schools would be closed?
Secondary substances are related to primary substances as formal principles of the latter.
Such entities, Aristotle says, are primary substances (2a11).
Moreover, because primary substances seem to be members of natural kinds, it is natural to interpret secondary substances as the kinds to which primary substances belong.
For, he thinks that a species in substance is said-of primary substances while species in the other categories are not said-of primary substances.
Primary substances are the substrate of existence of any other kinds of categorial being, as nothing exists in addition to primary substances but secondary substances and accidents, which both are forms present in individual substances.
And if there were no primary substances, there would be no "secondary" substances (species and genera), either.
As for the members of non-substance categories, they too depend for their existence on primary substances.
