This was originally given as a talk at The Metaphysics of Science: Causation and Natural Kinds, a workshop at the Panthéon-Sorbonne and the Institute for the History and Philosophy of Science and Technology, Paris, March 2014. The conference was organized by Andrew McFarland, who arranged for a special issue of Synthese on the same theme.
This version of the paper is revised for the special issue. Thanks to participants at the workshop and to K. Brad Wray for comments on earlier versions.
When we ask what natural kinds are, there are two different things we might have in mind. The first, which I'll call the taxonomy question, is what distinguishes a category which is a natural kind from an arbitrary class. The second, which I'll call the ontology question, is what manner of stuff there is that realizes the category. Many philosophers have systematically conflated the two questions. The confusion is exhibited both by essentialists and by philosophers who pose their accounts in terms of similarity. It also leads to misreading philosophers who do make the distinction. Distinguishing the questions allows for a more subtle understanding of both natural kinds and their underlying metaphysics.
@ARTICLE(magnus2015x,
AUTHOR = {P.D. Magnus},
TITLE = {Taxonomy, ontology, and natural kinds},
JOURNAL = {Synthese},
YEAR = {2018},
MONTH = apr,
VOLUME = {195},
NUMBER = {4},
PAGES = {1427--1439},
DOI = {10.1007/s11229-015-0785-2}
)
It was published on-line first under this DOI in July 2015.