In 1942 Haskell B.Curry presented what is now called Curry paradox which can be found in a logic independently of its stand on negation.In recent years there has been a revitalised interest in non-classical solutions to the semantic paradoxes. In this article the non-classical resolution of Currys Paradox and Shaw-Kwei paradox without rejection any contraction postulate is proposed.
We introduce a proper display calculus for first-order logic, of which we prove soundness, completeness, conservativity, subformula property and cut elimination via a Belnap-style metatheorem. All inference rules are closed under uniform substitution and are without side conditions.
Let $alphageq 2$ be any ordinal. We consider the class $mathsf{Drs}_{alpha}$ of relativized diagonal free set algebras of dimension $alpha$. With same technique, we prove several important results concerning this class. Among these results, we prove that almost all free algebras of $mathsf{Drs}_{alpha}$ are atomless, and none of these free algebras contains zero-dimensional elements other than zero and top element. The class $mathsf{Drs}_{alpha}$ corresponds to first order logic, without equality symbol, with $alpha$-many variables and on relativized semantics. Hence, in this variation of first order logic, there is no finitely axiomatizable, complete and consistent theory.
In this paper paraconsistent first-order logic LP^{#}_{omega} with infinite hierarchy levels of contradiction is proposed. Corresponding paraconsistent set theory KSth^{#}_{omega} is discussed.Axiomatical system HST^{#}_{omega} as paraconsistent generalization of Hrbacek set theory HST is considered.
Let 2<nleq l<m< omega. Let L_n denote first order logic restricted to the first n variables. We show that the omitting types theorem fails dramatically for the n--variable fragments of first order logic with respect to clique guarded semantics, and for its packed n--variable fragments. Both are modal fragments of L_n. As a sample, we show that if there exists a finite relation algebra with a so--called strong l--blur, and no m--dimensional relational basis, then there exists a countable, atomic and complete L_n theory T and type Gamma, such that Gamma is realizable in every so--called m--square model of T, but any witness isolating Gamma cannot use less than $l$ variables. An $m$--square model M of T gives a form of clique guarded semantics, where the parameter m, measures how locally well behaved M is. Every ordinary model is k--square for any n<k<omega, but the converse is not true. Any model M is omega--square, and the two notions are equivalent if M is countable. Such relation algebras are shown to exist for certain values of l and m like for nleq l<omega and m=omega, and for l=n and mgeq n+3. The case l=n and m=omega gives that the omitting types theorem fails for L_n with respect to (usual) Tarskian semantics: There is an atomic countable L_n theory T for which the single non--principal type consisting of co--atoms cannot be omitted in any model M of T. For n<omega, positive results on omitting types are obained for L_n by imposing extra conditions on the theories and/or the types omitted. Positive and negative results on omitting types are obtained for infinitary variants and extensions of L_{omega, omega}.