William Whewell, Cluster Theorist of Kinds

A dominant strand of philosophical thought holds that natural kinds are clusters of objects with shared properties. Cluster theories of natural kinds are often taken to be a late-twentieth-century development prompted by dissatisfaction with essentialism in philosophy of biology. I argue, however, that a cluster theory of kinds was formulated by William Whewell (1794–1866) more than a century earlier. Cluster theories of kinds can be characterized in terms of three central commitments, all of which are present in Whewell’s work on classification. Like contemporary cluster theorists, Whewell claims that kinds are united by similarity, that many kinds do not have essences, and that there are “gaps” between kinds. Moreover, Whewell advises taxonomists to look for consilience (roughly, convergence) between different classificatory schemes, a recommendation that reinforces the identification of natural classes with property clusters. Thus Whewell was not only an early cluster theorist but one with important insights into what a cluster theory of kinds means for the practice of classification.