 Wiggins and others argue that identity is dependent on a sortal in a weaker sense. The criterion for the identity of sets is perhaps the one clear and uncontroversial case: Two sets are identical, the same set, if and only if they have the same members. (Notice that while the criterion is clear, the appeal to identity reappears with reference to the members.) While it is perhaps less uncontroversial, my car is the same as the car I owned five years ago even though the oil, tires, battery and have been replaced; the car can remain the same even though some parts change. My friend is the same person as he was five years ago in spite of many natural changes in the molecules composing his body, some dental fillings, an artificial hip and a new cornea lens. Two natural numbers are the same if they gave the same successor, and two real numbers are identical iff they bear all of the same order relations to the other numbers, =3.14…. Notice that in all of these cases appeal to identity recurs with reference to parts (whether body or automotive) or relations to other objects of the same category. 