The Theory of ∑-Forms

III.1 The ∆-sentence-forms are those grounded forms none of whose descendants is of type or . The ∆-predicate-forms are those predicateforms the results of applying which to formal numerals are ∆-sentenceforms. The ∆-subject-forms are those subject-forms s such that α.s=α is a ∆-predicate-form (α being the first variable). The ∆-descriptor-forms are those descriptor-forms d such that, for some positive number n,

is a ∆-predicate-form (α1,…, αn+1 being the first n+1 variables).