Sets are mutually-disjoint if and only if there is no object that is a member of all of the sets.
(<=> (Mutually-Disjoint @Sets) (Empty (Intersection @Sets)))
(Empty (Intersection @Sets)) (Undefined (Arity Mutually-Disjoint))
(Instance-Of (Arity Mutually-Disjoint) Undefined) (<=> (Mutually-Disjoint @Sets) (Empty (Intersection @Sets)))