 The pride of place in this classificatory scheme, according to Aristotle, goes to those entities that are neither said-of nor present-in anything. Such entities, Aristotle says, are primary substances (2a11). Although he only gives a negative characterization of primary substances in the Categories — they are neither said-of nor present-in — the examples of them that he provides allow us to form a more robust conception of what a primary substance is supposed to be. His favorite examples are an individual man and a horse (1a20, 2a11). So, it is natural to interpret him as thinking that among primary substances are concrete particulars that are members of natural kinds. Whether in the Categories Aristotle intended to restrict the class of primary substances to just members of natural kinds turns out to be among the more controversial topics in Aristotle scholarship. But at the very least, he seems to think that members of natural kinds present enough of a paradigmatic case that he can use them as examples.