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JOURNALS // Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika // Archive

Izv. Vyssh. Uchebn. Zaved. Mat., 2020 Number 1, Pages 26–29 (Mi ivm9534)

A theories of classical propositional logic and counterimages of substitutions

I. A. Gorbunov

Tver State University, 33 Zhelyabov str., Tver, 170100 Russia

Abstract: We study theories based on the classical propositional logic. It follows from the lemma of Sushko's that for any classical propositional theory $T$ and substitution function $\varepsilon$ of formulas instead of propositional variables, the set $\varepsilon^{-1}(T)$ is also a classical propositional theory. In the paper, it is proved the following statement being more strong: for any consistent finitely axiomatized classical propositional theory $T$ there exists a substitution function $\varepsilon$ such that $T$ is a preimage of the set of all tautologies under $\varepsilon$. An algorithm of constructing of such a substitution function is given.

Keywords: lattice of theories of classical propositional logic, counterimages of substitutions, unification, Suszko's lemma.

UDC: 510.633

Received: 09.02.2019
Revised: 26.03.2019
Accepted: 27.03.2019

DOI: 10.26907/0021-3446-2020-1-26-29


 English version:
Russian Mathematics (Izvestiya VUZ. Matematika), 2020, 64:1, 22–24

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© Steklov Math. Inst. of RAS, 2024