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A generalization of the concept of ω-completeness1

Published online by Cambridge University Press:  12 March 2014

Leon Henkin*
Affiliation:
University of California, Berkeley

Extract

The concepts of ω-consistency and ω-completeness are closely related. The former concept has been generalized to notions of Γ-consistency and strong Γ-consistency, which are applicable not only to formal systems of number theory, but to all functional calculi containing individual constants; and in this general setting the semantical significance of these concepts has been studied. In the present work we carry out an analogous generalization for the concept of ω-completeness.

Suppose, then, that F is an applied functional calculus, and that Γ is a non-empty set of individual constants of F. We say that F is Γ-complete if, whenever B(x) is a formula (containing the single free individual variable x) such that ⊦ B(α) for every α in Γ, then also ⊦ (x)B(x). In the paper “Γ-con” a sequence of increasingly strong concepts, Γ-consistency, n = 1,2, 3,…, was introduced; and it is possible in a formal way to define corresponding concepts of Γn-completeness, as follows. We say that F is Γn-complete if, whenever B(x1,…, xn) is a formula (containing exactly n distinct free variables, namely x1…, xn) such that ⊦ B(α1,…,αn) for all α1,…,αn in Γ, then also ⊦ (X1)…(xn)B(x1,…,xn). However, unlike the situation encountered in the paper “Γ-con”, these definitions are not of interest – for the simple reason that F is Γn-complete if and only if it is Γ-complete, as one easily sees.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1957

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Footnotes

1

The research and writing of this paper have been supported in part by grants from the U.S. National Science Foundation. Under the title “Γ-completeness” the material contained in Theorems 1–3 was presented at the International Mathematical Congress held in Amsterdam in September, 1954. However, the abstract appearing in the published Proceedings of the Congress is in error; it should be corrected by replacing the last occurrence of “Γ” by an occurrence of .

21
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