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P.D. Magnus

Scurvy and the ontology of natural kinds

Considering the ontology which best fits a conception according to which natural kinds are the categories fit for enquiry, with scurvy and vitamin C as central examples. Accepted for presentation at the Philosophy of Science Association meeting in Pittsburgh, November 2022.

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Philosophers like Boyd, Magnus, and Franklin-Hall understand natural kinds to be the categories which are constraints on enquiry. In order to elaborate the metaphysics appropriate to such an account, I consider the example of scurvy and vitamin C. On a standard retelling, the cause and cure for scurvy was discovered in the 18th-century when citrus was shown to protect sailors. This superficial connection might be understood in terms of shallow metaphysics. However, it was unclear what about citrus was proof against scurvy. So scurvy was still a serious problem until the discovery of vitamin C in the 20th century. The standard essentialist move would identify the natural kind with the chemical structure of the vitamin. This fails because vitamins can comprise different chemical species or vitamers. These failures of shallow and deep metaphysics do not show that vitamins are not natural kinds. Instead, they show the value of middle-range ontology: starting from categories which we identify in the world, elaborating their structure to the extent that we can do so, but not pretending to jump ahead to a complete story about fundamental being.

The first on-line draft of this paper was posted 17dec2021.