Natural kinds

Objects belonging to a natural kind form a group of objects which have some theoretically important property in common. For example, rabbits form a natural kind, all samples of gold form another, and so on. Natural kinds are contrasted with arbitrary groups of objects such as the contents of dustbins, or collections of jewels. The latter have no theoretically important property in common: they have no unifying feature. Natural kinds provide a system for classifying objects. Scientists can then use this system to predict and explain the behaviour of those objects. For these reasons, the topic of natural kinds is of special interest to metaphysics and to the philosophy of science.