Intuitionistic Predicate Logic Research Articles

Some topological spaces which are universal for intuitionistic predicate logic

It is shown that for every formula which cannot be proved in intuitionistic predicate logic, and for every metrizable space X without isolated points one can find a sheaf model over X in which is not valid.

Partial isomorphisms and intuitionistic logic

A game for testing the equivalence of Kripke models with respect to finitary and infinitary intuitionistic predicate logic is introduced and applied to discuss a concept of categoricity for intuitionistic theories.

Innocuous substitutions

In classical first-order predicate logic CL1 (without equality) only tautologies and antitautologies satisfy nontautological schemas. I.e., if F[p, Q] is a nontautological formula (fl) in the predicate letters shown, with p prepositional, then ⊬ F[K, Q] for any sentence K not containing some Q ∈ Q, unless ⊢ K or ⊢ ¬K. This is an easy consequence of the Completeness Theorem. Clearly, the analogous statement fails for intuitionistic predicate logic IL1; already when Q is empty: (i) ¬¬ K for, e.g., K ≡ p ∨ ¬p; (ii) ¬¬K → K for, e.g., K ≡ ¬p.

Constructions of classical models by means of Kripke models (survey)

It is demonstrated how Kripke models for intuitionistic predicate logic can be applied in order to prove classical theorems. As examples proofs of the independence of the axiom of constructibility, of the omitting types theorem and of Shelah's ultrapower theorem are sketched.

Quine’s View(s) of Logical Truth

The effort to undermine the distinction between necessary and contingent truth is a theme that dominates Quine's work. It has led him to argue at length that the laws of logic have no special epistemic status, but his accounts of the topic show strains and apparent inconsistencies. My aim here is to clarify Quine's view of logical truth. The discussion will be largely confined to propositional logic. Predicate logic raises further problems about ontology and reference (see [17], 60-61), and anyway propositional logic generates the main philosophical issues. Kleene, for example, has traced the oddities of intuitionistic predicate logic and arithmetic to the replacement of the classical propositional

Craig's theorem in superintuitionistic logics and amalgamable varieties of pseudo-boolean algebras

In recent years there have appeared many studies of an interesting and important property of logical theories, the so-called Craig interpolation theorem. Craig proved the interpolation theorem for classical predicate logic in 1957 [9]. SchHtte [23] proved the interpolation theorem for intuitionistic predicate logic, and Gabbay [12] for certain extensions of this logic. In [I0, 13] the interpolation theorem was proved for a number of modal logics, and in [21] for many-valued predicate calculi.

A new version of Beth semantics for intuitionistic logic

We use the notation of Kripke's paper [1]. Let M = (G, K, R) be a tree structure and D a domain and η a Beth model on M. The truth conditions of the Beth semantics for ∨ and ∃ are (see [1]):(a) η (A ∨ B, H) = T iff for some B ⊆ K, B bars H and for each H′ ∈ B, either η(A, H′) = T or η(B, H′) = T.(b) η(∃xA(x), H) = T iff for some B ⊆ K, B bars H and for each H′ ∈ B there exists an a ∈ D such that η(A (a), H′) = T.Suppose we change the truth definition η to η* by replacing condition (b) by the condition (b*) (well known from the Kripke interpretation):Call this type of interpretation the new version of Beth semantics. We proveTheorem 1. Intuitionistic predicate logic is complete for the new version of the Beth semantics.Since Beth structures are of constant domains, and in the new version of Beth semantics the truth conditions for ∧, →, ∃, ∀, ¬ are the same as for the Kripke interpretation, we get:Corollary 2. The fragment without disjunction of the logic CD of constant domains (i.e. with the additional schema ∀x(A ∨ B(x))→ A ∨ ∀xB(x), x not free in A) equals the fragment without disjunction of intuitionistice logic.

Craig interpolation theorem for intuitionistic logic and extensions Part III

This is a continuation of two previous papers by the same title [2] and examines mainly the interpolation property for the logic CD with constant domains, i.e., the extension of the intuitionistic predicate logic with the schemaIt is known [3], [4] that this logic is complete for the class of all Kripke structures with constant domains.Theorem 47. The strong Robinson consistency theorem is not true for CD.Proof. Consider the following Kripke structure with constant domains. The set S of possible worlds is ω0, the set of positive integers. R is the natural ordering ≤. Let ω0 0 = , Bn, is a sequence of pairwise disjoint infinite sets. Let L0 be a language with the unary predicates P, P1 and consider the following extensions for P,P1 at the world m.(a) P is true on ⋃i≤2nBi, and P1 is true on ⋃i≤2n+1Bi for m = 2n.(b) P is true on ⋃i≤2nBi, and P1 for ⋃i≤2n+1Bi for m = 2n.Let (Δ,Θ) be the complete theory of this structure. Consider another unary predicate Q. Let L be the language with P, Q and let M be the language with P1, Q.

An intuitiomstic completeness theorem for intuitionistic predicate logic

The problem of treating the semantics of intuitionistic logic within the framework of intuitionistic mathematics was first attacked by E. W. Beth [1]. However, the completeness theorem he thought to have obtained, was not true, as was shown in detail in a report by V. H. Dyson and G. Kreisel [2]. Some vague remarks of Beth's, for instance in his book, The foundations of mathematics, show that he sustained the hope of restoring his proof. But arguments by K. Gödel and G. Kreisel gave people the feeling that an intuitionistic completeness theorem would be impossible [3]. (A (strong) completeness theorem would implyfor any primitive recursive predicate A of natural numbers, and one has no reason to believe this for the usual intuitionistic interpretation.) Nevertheless, the following contains a correct intuitionistic completeness theorem for intuitionistic predicate logic. So the old arguments by Godel and Kreisel should not work for the proposed semantical construction of intuitionistic logic. They do not, indeed. The reason is, loosely speaking, that negation is treated positively.Although Beth's semantical construction for intuitionistic logic was not satisfying from an intuitionistic point of view, it proved to be useful for the development of classical semantics for intuitionistic logic. A related and essentially equivalent classical semantics for intuitionistic logic was found by S. Kripke [4].

An intuitiomstic completeness theorem for intuitionistic predicate logic

The problem of treating the semantics of intuitionistic logic within the framework of intuitionistic mathematics was first attacked by E. W. Beth [1]. However, the completeness theorem he thought to have obtained, was not true, as was shown in detail in a report by V. H. Dyson and G. Kreisel [2]. Some vague remarks of Beth's, for instance in his book, The foundations of mathematics, show that he sustained the hope of restoring his proof. But arguments by K. Gödel and G. Kreisel gave people the feeling that an intuitionistic completeness theorem would be impossible [3]. (A (strong) completeness theorem would implyfor any primitive recursive predicate A of natural numbers, and one has no reason to believe this for the usual intuitionistic interpretation.) Nevertheless, the following contains a correct intuitionistic completeness theorem for intuitionistic predicate logic. So the old arguments by Godel and Kreisel should not work for the proposed semantical construction of intuitionistic logic. They do not, indeed. The reason is, loosely speaking, that negation is treated positively.Although Beth's semantical construction for intuitionistic logic was not satisfying from an intuitionistic point of view, it proved to be useful for the development of classical semantics for intuitionistic logic. A related and essentially equivalent classical semantics for intuitionistic logic was found by S. Kripke [4].

A logic stronger than intuitionism

S. A. Kripke has given [6] a very simple notion of model for intuitionistic predicate logic. Kripke's models consist of a quasi-ordering (C, ≤) and a function ψ which assigns to every c ∈ C a model of classical logic such that, if c ≤ c′, ψ(c′) is greater or equal to ψ(c). Grzegorczyk [3] described a class of models which is still simpler: he takes, for every ψ(c), the same universe. Grzegorczyk's semantics is not adequate for intuitionistic logic, since the formulawhere х is not free in α. holds in his models but is not intuitionistically provable. It is a conjecture of D. Klemke that intuitionistic predicate calculus, strengthened by the axiom scheme (D), is correct and complete with respect to Grzegorczyk's semantics. This has been proved independently by D. Klemke [5] by a Henkinlike method and me; another proof has been given by D. Gabbay [1]. Our proof uses lattice-theoretical methods.

Toshio Umezawa. On logics intermediate between intuitionistic and classical predicate logic. The journal of symbolic logic, vol. 24 no. 2 (for 1959, pub. 1960), pp. 141–153.

Toshio Umezawa. On logics intermediate between intuitionistic and classical predicate logic. The journal of symbolic logic, vol. 24 no. 2 (for 1959, pub. 1960), pp. 141–153.

Taboo Versus Axiom

Some important formal systems are really developable from a finite number of axioms in the lower classical predicate logic LK or in the intuitionistic predicate logic LJ. Any system of this kind can be developed in LK (or in LJ) from the single conjunction of all the axioms of the system.

A Formalism for Primitive Logic and Mechanical Proof-Checking

The universal character of the primitive logic LO in the sense that popular logics such as the lower classical predicate logic LK, the intuitionistic predicate logic LJ, Johansson’s minimal predicate logic LM, etc. can be faithfully interpreted in LO is very remarkable even from the view point of mechanical proof-checking. Since LO is very simple, deductions in LO could be mechanized in a simple form if a suitable formalism for LO is found out. Main purpose of this paper is to introduce a practical formalism for LO, practical in the sense that it is suitable at least for mechanical proof-checking business.

On Universal Character of the Primitive Logic

The PRIMITIVE LOGIC LO introduced in my former work is a logic having only two logical constants IMPLICATION → and UNIVERSAL QUANTIFICATION ( ) with their usual inference rules which are admitted even in the INTUITIONISTIC PREDICATE LOGIC LJ. LO is really a very simple logic, maybe the simplest possible logic as one can imagine, but it is very important because of its universal character. In fact, popular logics such as the LOWER CLASSICAL PREDICATE LOGIC LK, the INTUITIONISTIC PREDICATE LOGIC LJ, the MINIMAL PREDICATE .LOGIC LM, etc. can be faithfully interpreted in it. Speaking frankly, I am further expecting that all the important logics would be interpreted faithfully in it and would disclose their intrinsic characteristics by being interpreted in it. Main purpose of this paper is to show the universal character of the primitive logic LO by pointing out that a series of typical logics are faithfully interpretable in LO.

On weak completeness of intuitionistic predicate logic

Suppose the ri-placed relation symbols Pi, 1 ≦ i ≦ k, are all the non-logical constants occurring in the closed formula , also written as , of Heyting's predicate calculus (HPC). Then HPC is called complete for provided , i.e.Here D ranges over arbitrary species, and over arbitrary (possibly incompletely defined) subspecies of ;

On logics intermediate between intuitionistic and classical predicate logic

In [1] and [2] I investigated logics intermediate between intuitionistic and classical propositional logic. In the present paper I shall study inclusion and non-inclusion between certain intermediate predicate logics. All the logics considered result from intuitionistic predicate logic by addition of classically valid axiom schemes.