(<=> (Equivalence ?X) (Exists (?P1 ?P2) (And (Sentence ?P1) (Sentence ?P2) (= ?X (Listof (Quote <=>) ?P1 ?P2)))))
(Exists (?P1 ?P2) (And (Sentence ?P1) (Sentence ?P2) (= ?X (Listof (Quote <=>) ?P1 ?P2))))
(Exhaustive-Subclass-Partition Logsent (Setof Negation Conjunction Disjunction Implication Reverse-Implication Equivalence)) (<=> (Equivalence ?X) (Exists (?P1 ?P2) (And (Sentence ?P1) (Sentence ?P2) (= ?X (Listof (Quote <=>) ?P1 ?P2)))))