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Sentential Constants in Systems near R
Studia Logica: An International Journal for Symbolic Logic
Vol. 52, No. 3 (Aug., 1993), pp. 443-455
Published by: Springer
Stable URL: http://www.jstor.org/stable/20015685
Page Count: 13
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An Ackermann constant is a formula of sentential logic built up from the sentential constant t by closing under connectives. It is known that there are only finitely many non-equivalent Ackermann constants in the relevant logic R. In this paper it is shown that the most natural systems close to R but weaker than it-in particular the non-distributive system LR and the modalised system NR-allow infinitely many Ackermann constants to be distinguished. The argument in each case proceeds by construction of an algebraic model, infinite in the case of LR and of arbitrary finite size in the case of NR. The search for these models was aided by the computer program MaGIC (Matrix Generator for Implication Connectives) developed by the author at the Australian National University.
Studia Logica: An International Journal for Symbolic Logic © 1993 Springer