This chapter defends a commitment to an ontology of kinds for the special case of natural kinds; such a commitment plays an important role in motivating and underwriting the structure-based and restricted conception of parthood and composition outlined in the previous chapter. The special case of natural kinds is intended as an illustration of how a commitment to a certain class of kinds in general, or to specific kinds among them, may be generated on the basis of extra-mereological considerations. The belief in the existence of natural kinds, for example, may be supported by an appeal to their role in prediction and explanation; particularly noteworthy in this respect is the weight borne by scientific natural kinds (e.g., physical, chemical and biological kinds) in (i) inductive arguments, (ii) the laws of nature, and (iii) causal explanations.
Keywords: natural kinds, induction, projectibility, laws of nature, causation, physical kinds, chemical kinds, biological kinds, species, individuals,