Page "Metaphysics" Paragraph 21

Biological literature contains abundant references to taxa ( singular " taxon "), groups like the mammals or the poppies.

Some authors claim ( or at least presuppose ) that taxa are real entities, that to say that an animal is included in Mammalia ( the scientific name for the mammal group ) is to say that it bears a certain relation to Mammalia, an abstract object.

Advocates of phylogenetic nomenclature, a more nominalistic view, oppose this reading ; in their opinion, calling an animal a mammal is a shorthand way of saying that it is descended from the last common ancestor of, say, humans and platypuses.