The most serious form of this last worry centers on the semantics of the isa relation. The isa class subsumption relation is often presumed to hold in a context-general way and capture “purely ontological” relations; if it is true that “A isa B”, then any A in any context should by its nature be a B. Because our idea category is organized primarily by contingent semantic relationships holding only in the context of certain philosophical discussions, its isa links may fail to hold domain-generally and may conflate taxonomic and non-taxonomic relations.