The nature of natural kinds: Natural kinds in biology and medicine

Medicine and biology presuppose the division of diseases, organisms and events into categories. It is claimed that these categories are natural kinds. Our understanding of the ontological status of these kinds has serious ramifications for the study and practice of biology and medicine. Kinds realists claim that the success of biology and Western medicine can only be explained by understanding natural kinds as independently existing entities in the real world. Kinds anti-realists understand natural kinds as human creations, with no one grouping being more correct than any other.;I show that the kinds-reality debate is insoluble and argue that we can instead ask whether kinds are natural. I suggest two points of agreement between various interpretations of "naturalness": (1) Natural things behave independently of conscious human control; (2) Natural things behave regularly and predictably. A natural kind, therefore, is a group of natural objects which behaves with a regularity independent of conscious human activity. These regularities are described by natural laws. Kinds and laws are interdependent: natural laws require natural kinds for their formulation, and clusters of natural laws define natural kinds. Scientific theories are a combination of these interlocking laws and kinds. This picture of natural kinds preserves the merits of both kinds' realism and anti-realism: a natural kind is, in a sense, a construct, but one which can assist in scientific explanation and prediction.;Under this description, biological and medical kinds are natural kinds. Biological and medical laws perform the functions within biological and medical theories that other natural laws perform within the context of other scientific theories. Biological and medical kinds are natural kinds because they are appropriately related to natural laws within their theoretical context.;This view of natural kinds solves several puzzles in medicine and biology: (1) whether bacterial groupings constitute species, (2) why there is variability in the evidential standards for positing of undiscovered animal species, (3) why a "syndrome" differs medically from a "disease," (4) why giving simple criteria for "life" and "death" does not solve relevant medical ethics issues.