We can easily do without "vegetables", recognizing that many, but not all, consist of fruit, so that this category is obviously poorly constructed.It's more difficult to do without "fish", but the classification proposed by what is sometimes called "our best science", namely cladism, disputes that this name designates an actually existing group. In evolutionary biology, only the "clade" exists, a set of taxa all resulting from the same taxon - and "fish" is not so constructed. A first consequence of this affair is the divorce between the scientific division of the world and that in play in everyday life. Is it possible to conceive of a pluralism in which fish exists in certain respects, or must we, like vegetables, mourn its loss?
The second question I'd like to address concerns the role of the species concept in this classification. Evolutionary biology gives it a prominent role, since its major question in the twentiethcentury was speciation. But even before Darwin, the species has always been the only realistic taxon beyond simple organisms, since the criterion of inter-fertility, by which two individuals are recognized as being of the same species, suggests that we must attribute a kind of causal consistency to species. Should the ontology of a Darwinian biology admit, beyond species, other ontologically consistent taxa (such as clades?) for "natural genera" in the metaphysical sense? In order to address this question, we must first determine how our conception of the ontological status of the biological species - traditionally a class, but since David Hull an individual for many philosophers of biology - affects its formulation and possible resolution.
