A Defence of Pluralism in the Debate about Natural Kinds: Case Study from the Classification of Celestial Objects

I reconsider the monism/pluralism debate about natural kinds. Monism claims that there is a privileged division of reality into natural kinds, while pluralism states that there are many ways of classifying objects according to different purposes. I compare three different monistic accounts of natural kinds with the pluralism advocated by promiscuous realism. The analysis of some examples of the classification of celestial objects suggest that there are indeed different legitimate ways of classifying things according to different purposes; contrary to monism, the boundaries between kinds are not fixed. These results show that promiscuous realism is a better account of natural kind.