The subject formula includes the object formula. Formula A includes formula B if there exists some substitution which when applied to B creates a formula B' such that for every statement in B' is also in A, every variable universally (or existentially) quantified in B' is quantified in the same way in A. Variable substitution is applied recursively to nested compound terms such as formulae, lists and sets. (Understood natively by cwm when in in the antecedent of a rule. You can use this to peer inside nested formulae.)