Species are not explanatory kinds

Todd Grantham
College of Charleston, Dept of Philosophy

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     Last modified: February 15, 2005
     Presentation date: 07/14/2005 11:00 AM in ROZH 107
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Abstract
When Hull and Ghiselin first suggested that species are individuals, they invoked a simple dichotomy between classes and individuals. The waters have been thoroughly muddied since then. Philosophers and biologists now recognize a range of different "degrees" of individuality. Similarly, recent work on natural kinds has led to the realization that some classes are more robust than others. The general consensus is that species are neither robust kinds (because they do not have essences and do not figure in completely invariant laws) nor robust individuals (because they are not generally functionally integrated possessors of adaptations). Thus, the question is whether it is better to view species as weak individuals, weak kinds, or some hybrid. The strategy of this paper is to return to the question originally posed by Hull: do species function as kind terms within the laws of biology. Close examination of the role played by species in biological explanations shows that even though species taxa do function as "kinds" in a limited way (i.e., we use these kinds for inductive reasoning and prediction), species rarely function as kind terms in the explanatory generalizations of biology. This confirms some aspects of the "species as individuals" thesis. In particular, while historical lineages can be seen as HPC kinds for some inductive purposes (and very limited explanatory purposes), the "kind-like" aspects of species are best seen as deriving from the more fundamental ontological claim that species are lineages or historical entities.