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A formalization of the Lewis system S1 without rules of substitution.

Josep Pla Carrera (1979)


In the Lewis and Langford formalization of system S1 (1932), besides the deduction rules, the substitution rules are as well used: the uniform substitution and the substitution of strict equivalents. They then obtain systems S2, S3, S4 and S5 adding to the axioms of S1 a new axiom, respectively, without changing the deduction rules. Lemmon (1957) gives a new formalization of systems S1-S5, calling them P1-P5. Is is worthwhile to remark that in the formalization of P2-P5 one does not use any more...

A general deduction theorem.

Salvatore Guccione, Roberto Tortora (1980)


In this paper we present a very general deduction theorem which -based upon a uniform notion of proof from hypotheses- holds for a very large class of logical systems. Most of the known results for classical and modal logics, as well as new results, are immediate corollaries of this theorem.

A semantical hierarchy for modal formulas.

Salvatore Guccione, Roberto Tortora (1982)


In this paper a semantical partition, relative to Kripke models, is introduced for sets of formulas. Secondly, this partition is used to generate a semantical hierarchy for modal formulas. In particular some results are given for the propositional calculi T and S4.

An axiom system for incidence spatial geometry.

Rafael María Rubio, Alfonso Ríder (2008)


Incidence spatial geometry is based on three-sorted structures consisting of points, lines and planes together with three intersort binary relations between points and lines, lines and planes and points and planes. We introduce an equivalent one-sorted geometrical structure, called incidence spatial frame, which is suitable for modal considerations. We are going to prove completeness by SD-Theorem. Extensions to projective, affine and hyperbolic geometries are also considered.

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