PP200006: Iemhoff, Rosalie (2000) A(nother) characterization of Intuitionistic Propositional Logic. [Report]
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Abstract
In \cite{iemhoff} we gave a countable basis $\cal V$ for the
admissible rules of $\ipc$. Here we show that there is no proper
superintuitionistic logic with the disjunction property for which all
rules in $\cal V$ are admissible.
This shows that, relative to the disjunction property, $\ipc$ is
maximal with respect to its set of admissible rules. This
characterization of $\ipc$ is optimal in the sense that no finite
subset of $\cal V$ suffices. In fact, it is shown that for any finite
subset $X$ of $\cal V$, for one of the proper superintuitionistic
logics $D_n$ constructed by De Jongh and Gabbay (1974) all the rules
in $X$ are admissible. Moreover, the logic $D_n$ in question is even
characterized by $X$: it is the maximal superintuitionistic logic
containing $D_n$ with the disjunction property for which all rules in
$X$ are admissible.
Finally, the characterization of $\ipc$ is proved to be effective by
showing that it is effectively reducible to an effective
characterization of $\ipc$ in terms of the Kleene slash by De Jongh
(1970).
Item Type:  Report 

Report Nr:  PP200006 
Series Name:  Prepublication (PP) Series 
Year:  2000 
Date Deposited:  12 Oct 2016 14:36 
Last Modified:  12 Oct 2016 14:36 
URI:  https://eprints.illc.uva.nl/id/eprint/33 
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