 More precisely, one obtains a new object by abstracting it from some given kind of entities, in virtue of certain criteria of identity for this new (abstract) object. This abstraction is performed in terms of an equivalence relation defined on the given entities (see Wrigley 2006: 161). The celebrated slogan by Quine (1969: 23) “No entity without identity” is intended to express essentially the same understanding of an (abstract) object as an “item falling under a sortal concept which supplies a well-defined criterion of identity for its instances” (Lowe 1997: 619).