ABSTRACT
This chapter outlines the position of scientific essentialism, which develops an adequate metaphysics of scientific realism. The chemical kinds would all seem to belong in a natural hierarchy, the more general ones having essences that are included in those of the more specific. Given that this hierarchy of natural kinds exists, this is plausibly a significant fact about the world that should be reflected in any satisfactory ontology of scientific realism. The chapter also describes theory of natural kinds; outline an essentialist ontology based on this theory; and derive an essentialist theory of laws of nature that adequately explains their natural necessity and hierarchical structure. Natural kinds exist if and only if there are objective mind-independent kinds of things in nature. Hence, to believe in natural kinds one must believe that things are divided naturally into categorically distinct classes. The real essences of natural kinds are to be distinguished from their nominal essences.
