We have entered upon the final Ennead! To be honest I didn't think it'd take me nearly a year to get this far—the book is not a large one—but it requires a tremendous amount of intellectual energy merely to engage with. Looking back over my summaries so far, I see a rather embarrassing number of obvious mistakes, inconsistencies, and attempted-shoehorning of Plotinus' position into ill-fitting schema. I reiterate my plea that if you find any of this interesting, that you please attempt to read Plotinus directly, rather than trust my summaries. I will need to do another pass over them at some point and correct myself.
Anyway, to business: you will have to forgive my glossing over this chapter, which is a primarily a critique of Aristotle's Categories: Aristotle is the second most important contributor to Western thought, the Categories are perhaps his most enduring and controversial contribution, I have studied neither, and the discussion is of a highly technical nature. I'm simply not up to the task with the knowledge I presently possess.
VI 1: On the Kinds of Being (1)
Aristotle posits ten "categories" for things that exist by examining how we communicate about them. But communication isn't the same as reality, and the analysis applied to one can't necessarily by applied to the other; indeed, even under generous assumptions, doing so sometimes produces absurdities. So while these categories may have logical merit, and indeed provide a useful starting place for investigation of what actually exists, we must dismiss Aristotle's classification as inaccurate.
In a similar manner, the Stoics posit four categories for things that exist. However, their error is more fundamental: underlying their choice of categories is the assumption that matter is the all that exists, which we have refuted at great length elsewhere. Even granting this, however, the ontological problems present in their scheme are insurmountable. Therefore, we must dismiss the Stoic classification as well.
Call me petty, but I was rather amused by Plotinus' dressing-down of the Stoics in §§26–28.