The word, “fish”, is not the real issue. What actually matters is that including dolphins in that category leads to making incorrect inferential predictions (“Salmon, guppies, sharks, and trout all lay eggs, so dolphins probably do too.”) as well as weakening the ability to make correct ones (“Do trout have gills? Well, salmon do, but dolphins don’t, so who knows.”)
What kinds of properties is your “aquatic animals” category better at predicting? (And “living in water” doesn’t count, because that’s what you have to already know to see if something’s in the category.)
The word, “fish”, is not the real issue. What actually matters is that including dolphins in that category leads to making incorrect inferential predictions (“Salmon, guppies, sharks, and trout all lay eggs, so dolphins probably do too.”) as well as weakening the ability to make correct ones (“Do trout have gills? Well, salmon do, but dolphins don’t, so who knows.”)
What kinds of properties is your “aquatic animals” category better at predicting? (And “living in water” doesn’t count, because that’s what you have to already know to see if something’s in the category.)