The paper considers certain properties of intermediate and moda propositional logics.The first part contains a proof of the theorem stating that each intermediate logic is closed under the Kreisel-Putnam rule xyz/(xy)(xz).

LetL 3 c be the smallest set of propositional formulas, which containsCpCqpCCCpqCrqCCqpCrpCCCpqCCqrqCCCpqppand is closed with respect to substitution and detachment. Let $\mathfrak{M}_3^c $ be Łukasiewicz’s three-valued implicational matrix defined as follows:cxy=min (1,1−x+y), where $x,y \in \{ 0,\tfrac{1}{2},1\}$ . In this paper the following theorem is proved: $$L_3^c = E( \mathfrak{M}_3^c )$$ The idea used in the proof is derived from Asser’s proof of completeness of the two-valued propositional calculus. The proof given here is based on the Pogorzelski’s deduction theorem fork-valued (...) propositional calculi and on Lindenbaum’s theorem. (shrink)

In this paper it is shown that there exist a structural complete interme- diate logics with the disjunction property, which was previously conjectured by H. Friedman. The intermedi.