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.
'(Exists (?U) (And (Bounded ?U) (Not (Empty ?U)) (Forall (?X) (=> (Member ?X ?U) (Exists (?Y) (And (Member ?Y ?U) (Proper-Subset ?X ?Y)))))))