Continuing on the Categories, in this preview we finish up our discussion of substance by talking about artifacts: Only "genuine unities" are substances, and hammers and cups, for Aristotle, don't count as such unities. Should being a cup be considered instead a property like being white? Can properties be complex?
We're actually not sure about natural objects like rivers, mountains, etc. Are these natural unities, or just a way we cut up the world that is useful to us? We have more questions than answers!
One tool Aristotle provides for decoding this is to ask about the relation between an individual and the definition of its descriptor. So if Socrates is an individual person, and the definition of person is, as Aristotle says, "a rational animal," then Socrates is a rational animal. Let's say Socrates is also white, and the definition of white is "the lightest color," well, Socrates isn't a color at all, so this shows that saying someone is a person is a different kind of attribution than saying someone is white.
However, this may not actually work. If I say Socrates is wet, then the definition of wet can be just given as "having a lot of moisture," and sure, that still describes the wet Socrates. The difference is that I didn't say that wetness is "a state of having a lot of moisture," in which case I could say that no, Socrates is not a state.
To return to the examples above that we use in the episode, why not define white instead of as "a color that..." (e.g. reflects light at such and such a wavelength; we're not sure what kind of definition Aristotle would actually give) but as "having the quality of..." And yes, a white Socrates has the quality of reflecting the light or whatever. Conversely, if instead of defining person as "rational animal," we define person as "a species within the genus animal distinguished by the differentia rational," then no, Socrates is not a species. So this tool that Aristotle spends such time on to justify genus and species as being secondary substances while other descriptors are properties doesn't actually work.
This is just one of many interpretive puzzles that this text suggests, and in the full episode we try our best to get through all the Categories and make sense of the project.