ecause those can only have classes as members -- is this correct?

But if this is so, then why does Sowa's upper ontology put these meta-classes in the same lattice (intersecting with) classes of individuals such as Physical, Abstract, Continuant, and Occurrent?  Is this a mistake, or how am I to understand this lattice?  Is it possible that Sowa intends Physical, Abstract, Continuant, and Occurrent to be meta-classes too, so that his entire ontology is a classification of types, not of individuals?  But hi