Naturalized Metaphysics and the Contention over the Ontological Status of Species
Matthew H. Slater
NATURALIZED METAPHYSICS AND THE METAPHYSICS OF SPECIES
In their classic text on plant evolution, botanists Briggs and Walters asked, “When we look at nature, are the ‘units’ we recognise and name already there to be recognised or have we ‘made’ them in the process of looking?” (1997, 361). Are species, in other words, real?1 Assuming that species are real and there to be discovered in advance of our efforts to name and characterize them, what sorts of things are they? As Michael Ruse once asked, are they “natural kinds, individuals, or what?” (1987).
Such questions concerning the metaphysics of species raise issues that are paradigm instances of scientific metaphysics (or as Kyle Stanford might prefer, “the metaphysics of science”; see chap. 7 of this volume). As such, the general topic seems a fine test case for proposals on how best to “naturalize” metaphysics, particularly if considering them might help us get more precise about what naturalized metaphysics is and why it is supposed to be more valuable than non-naturalistic (or “analytic” or “speculative”) metaphysics. Yet no one (to my knowledge) has explored the relevance of the species-metaphysics debate to broader questions about the status 
of naturalized metaphysics debate in any detail. This is somewhat surprising given that arguments in these debates appeal to explicitly naturalistic considerations. Defenders of the dominant metaphysics of species, the Species-as-Individuals (SAI) thesis, often center their arguments for SAI on its tight relationship with common practices in systematics—in purported contrast with competing views that diverge from scientific practice in important ways. Moreover, the contending views in this domain directly intersect with subjects of independent, long-standing metaphysical interest (such as mereology, natural kinds, theories of properties, natural laws, and so on).
One might attempt to explain this lack of attention by pointing out that inasmuch as SAI-ists clearly and loudly prioritize their connection with hard-nosed, ground-level science over airy metaphysics, the case will fall squarely within naturalist territory and will thus be relatively unrevealing about the outer frontiers of a properly naturalized metaphysics. This assumption, I argue, is mistaken. Though generally sympathetic to naturalism—vague and amorphous though it is for me at this point—I do not believe that SAI represents a very clear case for the naturalist. My hope is that this unclarity makes it an interesting and potentially revealing case.
The reason that SAI is an interesting case for considering naturalized metaphysics is, in part, because it is false—or so I have previously argued at length elsewhere (Slater 2013, §54.1-5.3). Now, this conclusion (if it holds up) tells us little itself about the twin conceptual and methodological questions of what naturalized metaphysics is and how it should be justified and pursued. After all, naturalists need not guarantee that uncontroversial metaphysical characterizations of the relevant science will be easily derived from that science—even for cases apparently well within the naturalist’s wheelhouse. (Nor, more obviously still, should they guarantee that all of the science on which metaphysical claims are premised is true.) However, I will argue that the particular grounds for taking SAI to be false turn out to be revealing for efforts to naturalize metaphysics, for they are largely metaphysical and a priori in character. Thus, if I am right about SAI, we cannot expect to carry off the project of naturalizing metaphysics simply by always insisting that scientific considerations should trump prior metaphysical convictions; metaphysical convictions may sometimes take priority.
Now, of course, I might be wrong about SAI. My space here to make the case is limited, so I shall have to settle for a mere sketch of the argument. If I am wrong, then I offer the case as a schematic depiction of what seems to be a genuinely open possibility—a cautionary fable, if you like. As a consequence, it seems to me that naturalized metaphysics will require a more subtle and open-textured characterization than has yet been offered, and (as a result) will not be very useful as an all-purpose club against a prioristic analytic metaphysics (or against scientific ontologies that adduce reasons falling under that umbrella in their support). We might do better to cleave to the spirit and motivations of naturalized metaphysics, in its full application across the sciences, by assuming a more flexible, pragmatic stance about what counts as good and what bad in the metaphysics of science.
-  As Coyne and Orr point out, “Most biologists certainly act as if species are real... . Yet a vocal group of biologists, including many botanists, dissent, claiming that species are subjective divisions of nature made for humanconvenience” (2004, 9).