Kripke argues for origin essentialism, the view that the same individual cannot have multiple origins. Sober hypothesises that Kripke's origin essentialism applies to biological species. This paper shows that Sober's hypothesis fails. Because Kripke's original argument is invalid, it cannot vindicate Sober's proposal. Salmon offers an influential reformulation of Kripke's argument but his argument fails to extend to species: the notion of an individual's origin is too narrow to apply to species, and Salmon's argument rests on a thought experiment that (...) conflicts with how species evolve. Thus, Sober and others are wrong to think that Kripke's origin essentialism can save species essentialism. (shrink)

de Queiroz (1995), Griffiths (1999) and LaPorte (2004) offer a new version of essentialism called "historical essentialism". According to this version of essentialism, relations of common ancestry are essential features of biological taxa. The main type of argument for this essentialism proposed by Griffiths (1999) and LaPorte (2004) is that the dominant school of classification, cladism, defines biological taxa in terms of common ancestry. The goal of this paper is to show that this argument for historical essentialism is unsatisfactory: cladism (...) does not assume that relations of common ancestry are essential attributes of biological taxa. Therefore, historical essentialism is not justified by cladism. (shrink)

The view that species are individuals, as developed by Ghiselinand Hull, has been touted as explaining the role of type specimens intaxonomy. The kinship of this explanation with the Kripke-Putnam theoryof names has long been recognized. In light of this kinship, however,Hull's account of type specimens can be seen to entail two relatedinscrutability problems – unreasonable limits placed on the natureand extent of biological knowledge. An appreciation for these problemsinvites us to consider the proper relation between metaphysical andepistemological inquires in (...) the philosophy of science. (shrink)

Although naming biological clades is a major activity in taxonomy, little attention has been paid to what these names actually refer to. In philosophy, definite descriptions have long been considered equivalent to the meaning of names and biological taxonomy is a scientific application of these ideas. One problem with definite descriptions as the meanings of names is that the name will refer to whatever fits the description rather than the intended individual (clade). Recent proposals for explicit phylogenetic definitions of clade (...) names suffer from similar problems and we argue that clade names cannot be defined since they lack intension. Furthermore we stress the importance of tree-thinking for phylogenetic reference to work properly. (shrink)

Type specimens are used to designate species. What is the nature of the relation between a type specimen and the species it designates? If species names are rigid designators, and type specimens ostensively define species, then that relation is, at the very least, a close one. Levine :325–338, 2001) argues that the relationship of type specimen to a named species is one of necessity—and that this presents problems for the individuality thesis. Namely, it seems odd that a contingently selected specimen (...) should belong to a species of necessity. In considering Levine’s argument, LaPorte suggests that recognizing the distinction between de re and de dicto necessity resolves Levine’s worries. I reconsider the motivating question: does a type specimen belong of necessity to the species that it designates? In light of taxonomic cases and practice the answer is clear: definitively not. This is particularly clear in the case of re-designation of types by taxonomic decree. I explain how this helps reveal how taxonomists prioritize competing theoretical commitments, and offer a defense of the individuality thesis as applied to these particular cases. In short, I demonstrate how to misidentify a type specimen. (shrink)

The so-called ‘type method’ widely employed in biological taxonomy is often seen as conforming to the causal-historical theory of reference. In this paper, I argue for an alternative account of reference for biological nomenclature in which taxon names are understood as descriptive names. A descriptive name, as the concept came to be known from the work of Gareth Evans, is a referring expression introduced by a definite description. There are three main differences between the DN and the causal account. First, (...) according to the DN account, rather than fixing a name to a referent, the assignment of a type specimen to serve as the name-bearer for a taxon should be seen as performatively establishing a synonymy between a name and a definite description of the form “the taxon whose type is t”. Each taxon name is therefore associated with a criterion of application, a semantic rule that establishes the connection between the name and the descriptive content. This is the second major difference from the causal account: taxon names do have some descriptive content associated with them. The final locus of dissent concerns the strength of the modality resulting from the usage of taxon names. In order to address this point, I use the DN account to focus on the debate between Matt Haber and Joeri Witteveen concerning misidentification of type specimens, misapplication of names, and the truth conditions of Joseph LaPorte’s de dicto necessary sentence “Necessarily, any species with a type specimen contains its type specimen”. Using a pragmatic variant of the distinction between attributive and referential uses of descriptions, I argue that a metalinguistic version of the de dicto sentence is in fact falsified, as previously argued by Haber. (shrink)

Humeans and non-Humeans reasonably agree that there may be necessary connections between entities that are identical or merely partly distinct—between, e.g., sets and their individual members, fusions and their individual parts, instances of determinates and determinables, members of certain natural kinds and certain of their intrinsic properties, and (especially among physicalists) certain physical and mental states. Humeans maintain, however, that as per “Hume’s Dictum”, there are no necessary connections between entities that are wholly distinct;1 and in particular, no necessary causal (...) connections between such entities (even when the background conditions requisite for causation are in place). The Humean’s differential treatment appears principled, in reflecting that commonly accepted necessary connections involve constitutional relations, whereas wholly distinct entities (notably, causes and effects) do not constitute each other. I’ll argue, however, that the appearance of principle is not genuine, as per the following conditional: Constitutional→Causal: If one accepts certain constitutional necessities, one should accept certain causal necessities. This result provides needed leverage in assessing the two main frameworks in the metaphysics of science, treating natural kinds, causes, laws of nature, and the like. These frameworks differ primarily on whether Hume’s Dictum is taken as a working constraint on theorizing; and it has proved difficult for either side to criticize the other without presupposing their preferred stance on the dictum, hence talking past one another. The arguments for Constitutional→Causal are based, however, in general and independent considerations about what facts in the world might plausibly warrant our beliefs in certain constitutional necessities involving broadly scientific entities. The Humean can respond to these arguments, which reveal a deep tension in their view, at attendant costs of implausibilty and adhocery. The non-Humean framework doesn’t face any such tension between constitutional and causal necessities, however, and so in this respect comes out ahead. (shrink)

Species are central to biology, but there is currently no agreement on what the adequate species concept should be, and many have adopted a pluralist stance: different species concepts will be required for different purposes. This thesis is a multidimensional analysis of species pluralism. First I explicate how pluralism differs monism and relativism. I then consider the history of species pluralism. I argue that we must re-frame the species problem, and that re-evaluating Aristotle's role in the histories of systematics can (...) shed light on pluralism. Next I consider different forms of pluralism: evolutionary and extra-evolutionary species pluralism, which differ in their stance on evolutionary theory. I show that pluralism is more than a debate about the species category, but a debate about which concepts are legitimate and a claim about how they interact with one another. Following that, I consider what sort of ontology is required for different forms of species pluralism. I argue that pluralists who deny the unity of biology will require a further plurality of frameworks, while those that ground their pluralism in evolution need only one framework. Finally, I consider what pluralism means for biological practice. I argue that species concepts are tools, and reflect on how pluralism can illuminate the way systematists approach the discovery of new species of yeast. Pluralism can make sense of the way species concepts are used, and can be developed to aid researchers in thinking about how to use the right tools for the right jobs. (shrink)