Amorphic kinds: Cluster’s last stand?

I raise a puzzle case for “cluster” accounts of natural kinds—the homeostatic property cluster and stable property cluster accounts, especially—on the basis of their expected treatment of the metaphysics of certain disease kinds. Some kinds, I argue, fail to exhibit the co-instantiated property clusters these cluster views take to be (partly) constitutive of natural kinds. Some genetic diseases, for example, have archetypical instances with few or none of the pathological processes or symptoms associated with the kind: their instances are typified by a single dispositional property. I dub such kinds ‘amorphic’, owing to their limited morphology, and try out a number of ways in which these kinds might be treated in terms of property clusters, adapting responses cluster theorists have offered to the problem of polymorphic species. Finding these responses wanting, I conclude that cluster accounts are unlikely to be the best account of the metaphysics of amorphic kinds.