Abstract: | A set-theoretic LST system based on a logic without rules of contraction of identical formulas in the antecedent or succedent
of sequents is introduced. The set-theoretic axioms used are the comprehension principle,, where the weight of the variablex in the formulaA(x) is at most one (see below), and the extensionality principle,.
It is proved that the restriction on the weight of the variablex in the comprehension axiom is essential. Examples of comprehension axioms with the weight of variablex equal to 2 whose combination with the extensionality principle leads to a contradiction in the logic without contraction
rules are constructed.
Translated fromMatematicheskie Zametki, Vol. 66, No. 5, pp. 643–652, November, 1999. |