[Final version before copyediting. Published in Perspectives on Social Ontology and Social

A kind, according to Aristotle, is what makes an individual entity be what it is. I am what I am in virtue of belonging to the kind “human being”, and of having essential properties like the capacity to think and talk to other members of my species. These properties according to Aristotle are given by nature – not by us. Scientific knowledge is knowledge of these essential properties. Science aims at discovering the nature of things. This Aristotelian conception of kinds is held only by a minority of contemporary philosophers. The term “kind ” however is still widely in use, both in metaphysics and in the philosophy of science. The language of kinds is associated with the idea that the world comes already structured before we look at it. There are natural ways of classifying things, classifications that are independent of our theories. Some philosophers identify natural kinds with the categories of our most advanced scientific theories. These “scientific ” kinds, unlike other classifications, support robust and reliable inductive inferences. 1 Other philosophers in contrast emphasise essential properties, and the idea that natura