**Defined in theory: Kif-sets****Source code: kif-sets.lisp**

**Documentation:**There is a bounded set containing a set, a set that properly contains that set, a third set that properly contains the second set, and so forth. In short, there is at least one bounded set of infinite cardinality.

**Instance-Of:**Sentence**Defining-Axiom:**'(Exists (?U) (And (Bounded ?U) (Not (Empty ?U)) (Forall (?X) (=> (Member ?X ?U) (Exists (?Y) (And (Member ?Y ?U) (Proper-Subset ?X ?Y)))))))

**Source:**KIF Version 3.0 Specification