It is not certain when or by whomandwere first technically distinguished asgenusandspecies. The distinction does not appear in Plato's extant writings, whereas Aristotle seems to take it for granted in theTopics, which is usually regarded as among his earliest treatises. In his dialogues Plato seems able to useinterchangeably to denote any group or division in a diairesis, including the group that is to be divided.

Aristotle refers to some animal kinds as μέγιστα γένη, or greatest kinds. The goal of this paper is to make clear the nature and significance of these kinds. I argue that Aristotle thinks of greatest kinds as the most general kinds within a specified domain. I then consider the fact that Aristotle’s discussion of animals’ reproductive parts and modes of reproduction in Generation of Animals is organized around divisions related to the cause of each of the features being explained. I (...) conclude that, while classification is an important goal in Aristotle’s biological treatises, it is of little significance that some of the kinds he identifies are referred to as greatest kinds. The important divisions are, for Aristotle, the divisions that best serve his goal of explaining the various features of animals and these divisions sometimes group together and sometimes cut across the commonly recognized, including the greatest, animal kinds. (shrink)

In this paper I explore Aristotle’s views on natural kinds and the compatibility of pluralism and realism, a topic that has generated considerable interest among contemporary philosophers. I argue that, when it came to zoology, Aristotle denied that there is only one way of organizing the diversity of the living world into natural kinds that will yield a single, unified system of classification. Instead, living things can be grouped and regrouped into various cross-cutting kinds on the basis of objective similarities (...) and differences in ways that subserve the explanatory context. Since the explanatory aims of zoology are diverse and variegated, the kinds it recognizes must be equally diverse and variegated. At the same time, there are certain constraints on which kinds can be selected. And those constraints derive more from the causal structure of the world than from the proclivities of the classifier (hence the realism). This distinguishes Aristotle’s version of pluralistic realism from those contemporary versions (like Dupré’s “promiscuous realism”) that treat all or most classifications of a given domain as equally legitimate and not just a sub-set of kinds recognized by the science that studies it. By contrast, Aristotle privileges scientifically important kinds on the basis of their role in causal investigations. On this picture natural kinds are those kinds with the sort of causal structure that allows them to enter into scientific explanations. In the final section I argue that Aristotle’s zoology should remain of interest to philosophers and biologists alike insofar as it combines a pluralistic form of realism with a rank-free approach to classification. (shrink)