ABSTRACT
What difference does the application of mathematical formalism make to the notion of natural kinds? In this chapter I investigate the practice of applied mathematics as part of the practice of constructing natural kinds, and I argue that natural kinds are practiced and that the natural realism they are embedded in is best understood as a kind of practice, better yet, a tangle of mutually reinforcing practices. Natural kinds are deeply embedded in local contexts of instrumental practices of application and construction, formal and nonformal, inseparably, informed by criteria, standards, aims, and so on. Through the complex dynamics of performances, natural kinds are deeply practiced.
