> The word "fish" has a well established meaning But that is precisely the matter of contention. Even in the domain of biology, you have two systems of nomenc

> The word "fish" has a well established meaning But that is precisely the matter of contention. Even in the domain of biology, you have two systems of nomenclature, traditional and cladistic, in which animals may be classified differently. Furthermore, some animals that are not considered fish under either the traditional or cladistic systems have gills, so fishiness is clearly not a simple matter of gilliness. Crabs are an obvious example, as crustaceans they are certainly not fish, yet they have gills, live in the water (often, though not always) and are called shellfish. Hermitcrabs are an example of crabs with gills that are primarily terrestrial... or are they? Are hermit crabs actually crabs? Like fish, there is a wide variety of animals which are casually called crabs, but which are not 'true crabs' according to biologists today. Many popular crabs fall into this category, for instance king crabs. When is the last time you heard somebody go off on a "Well actually, that's not crab you're eating" rant? Not often, not nearly as often as 'whales aren't fish' rants anyway. Why is the fish/whale dichotomy emotionally important to people while the crab/crablike distinction is something almost nobody knows or cares about? I am pretty sure it's because people want to protect whales by disassociating them from food (fish.) Regardless, these non-crabs are called crabs because they have the distinctly crabby qualities people look for in crabs; claws, exoskeletons, and a generally spidery body shape (disqualifying lobsters.) The term to describe the phenomenon of non-crabs becoming ''crabs'' is 'carcinisation', a term described by it's creator as "one of the many attempts of Nature to evolve a crab" For this concept to have any coherence, we must have some notion of crab that transcends the true crab. We could call that 'crabbiness', similar to the way I can call a whale 'fishy'. > It has to do with being a member of a class of creatures that share certain characteristics The selection of which traits to consider is where human culture leaves it's mark. In a different culture, you might make the claim that some fish have gills and some do not. In a different culture you might say that only bony fish with swim bladders are 'true fish' and that cartilaginous swimming creatures without swim bladders aren't fish at all. If having a swim bladder is what our culture considers fishy, then sharks are no longer fish. But in our extant culture, some fish have swim bladders and some fish do not.