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  1. Proof-theoretic conservations of weak weak intuitionistic constructive set theories.Lev Gordeev - 2013 - Annals of Pure and Applied Logic 164 (12):1274-1292.
    The paper aims to provide precise proof theoretic characterizations of Myhill–Friedman-style “weak” constructive extensional set theories and Aczel–Rathjen analogous constructive set theories both enriched by Mostowski-style collapsing axioms and/or related anti-foundation axioms. The main results include full intuitionistic conservations over the corresponding purely arithmetical formalisms that are well known in the reverse mathematics – which strengthens analogous results obtained by the author in the 80s. The present research was inspired by the more recent Sato-style “weak weak” classical extensional set theories (...)
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  • Reflections on reflections in explicit mathematics.Gerhard Jäger & Thomas Strahm - 2005 - Annals of Pure and Applied Logic 136 (1-2):116-133.
    We give a broad discussion of reflection principles in explicit mathematics, thereby addressing various kinds of universe existence principles. The proof-theoretic strength of the relevant systems of explicit mathematics is couched in terms of suitable extensions of Kripke–Platek set theory.
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  • Universes in explicit mathematics.Gerhard Jäger, Reinhard Kahle & Thomas Studer - 2001 - Annals of Pure and Applied Logic 109 (3):141-162.
    This paper deals with universes in explicit mathematics. After introducing some basic definitions, the limit axiom and possible ordering principles for universes are discussed. Later, we turn to least universes, strictness and name induction. Special emphasis is put on theories for explicit mathematics with universes which are proof-theoretically equivalent to Feferman's.
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  • Extending the system T0 of explicit mathematics: the limit and Mahlo axioms.Gerhard Jäger & Thomas Studer - 2002 - Annals of Pure and Applied Logic 114 (1-3):79-101.
    In this paper we discuss extensions of Feferman's theory T 0 for explicit mathematics by the so-called limit and Mahlo axioms and present a novel approach to constructing natural recursion-theoretic models for systems of explicit mathematics which is based on nonmonotone inductive definitions.
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  • Full operational set theory with unbounded existential quantification and power set.Gerhard Jäger - 2009 - Annals of Pure and Applied Logic 160 (1):33-52.
    We study the extension of Feferman’s operational set theory provided by adding operational versions of unbounded existential quantification and power set and determine its proof-theoretic strength in terms of a suitable theory of sets and classes.
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  • (1 other version)A version of kripke‐platek set theory which is conservative over peano arithmetic.Gerhard Jäger - 1984 - Mathematical Logic Quarterly 30 (1‐6):3-9.
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  • Subsystems of Second Order Arithmetic.Stephen G. Simpson - 1999 - Studia Logica 77 (1):129-129.
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  • (1 other version)Upper Bounds for metapredicative mahlo in explicit mathematics and admissible set theory.Gerhard Jäger & Thomas Strahm - 2001 - Journal of Symbolic Logic 66 (2):935-958.
    In this article we introduce systems for metapredicative Mahlo in explicit mathematics and admissible set theory. The exact upper proof-theoretic bounds of these systems are established.
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  • Forcing in proof theory.Jeremy Avigad - 2004 - Bulletin of Symbolic Logic 10 (3):305-333.
    Paul Cohen’s method of forcing, together with Saul Kripke’s related semantics for modal and intuitionistic logic, has had profound effects on a number of branches of mathematical logic, from set theory and model theory to constructive and categorical logic. Here, I argue that forcing also has a place in traditional Hilbert-style proof theory, where the goal is to formalize portions of ordinary mathematics in restricted axiomatic theories, and study those theories in constructive or syntactic terms. I will discuss the aspects (...)
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  • (1 other version)Interpreting classical theories in constructive ones.Jeremy Avigad - 2000 - Journal of Symbolic Logic 65 (4):1785-1812.
    A number of classical theories are interpreted in analogous theories that are based on intuitionistic logic. The classical theories considered include subsystems of first- and second-order arithmetic, bounded arithmetic, and admissible set theory.
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  • On Feferman’s operational set theory OST.Gerhard Jäger - 2007 - Annals of Pure and Applied Logic 150 (1-3):19-39.
    We study and some of its most important extensions primarily from a proof-theoretic perspective, determine their consistency strengths by exhibiting equivalent systems in the realm of traditional set theory and introduce a new and interesting extension of which is conservative over.
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  • (4 other versions)The theory of functions.L. Gordeev - 1988 - Annals of Pure and Applied Logic 38 (1):26.
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  • (4 other versions)The theory of functions and classes. Part I.L. Gordeev - 1988 - Annals of Pure and Applied Logic 38 (1):66.
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  • The strength of Mac Lane set theory.A. R. D. Mathias - 2001 - Annals of Pure and Applied Logic 110 (1-3):107-234.
    Saunders Mac Lane has drawn attention many times, particularly in his book Mathematics: Form and Function, to the system of set theory of which the axioms are Extensionality, Null Set, Pairing, Union, Infinity, Power Set, Restricted Separation, Foundation, and Choice, to which system, afforced by the principle, , of Transitive Containment, we shall refer as . His system is naturally related to systems derived from topos-theoretic notions concerning the category of sets, and is, as Mac Lane emphasises, one that is (...)
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  • The predicative Frege hierarchy.Albert Visser - 2009 - Annals of Pure and Applied Logic 160 (2):129-153.
    In this paper, we characterize the strength of the predicative Frege hierarchy, , introduced by John Burgess in his book [J. Burgess, Fixing frege, in: Princeton Monographs in Philosophy, Princeton University Press, Princeton, 2005]. We show that and are mutually interpretable. It follows that is mutually interpretable with Q. This fact was proved earlier by Mihai Ganea in [M. Ganea, Burgess’ PV is Robinson’s Q, The Journal of Symbolic Logic 72 619–624] using a different proof. Another consequence of the our (...)
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  • Operational closure and stability.Gerhard Jäger - 2013 - Annals of Pure and Applied Logic 164 (7-8):813-821.
    In this article we introduce and study the notion of operational closure: a transitive set d is called operationally closed iff it contains all constants of OST and any operation f∈d applied to an element a∈d yields an element fa∈d, provided that f applied to a has a value at all. We will show that there is a direct relationship between operational closure and stability in the sense that operationally closed sets behave like Σ1 substructures of the universe. This leads (...)
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  • Forcing under Anti‐Foundation Axiom: An expression of the stalks.Sato Kentaro - 2006 - Mathematical Logic Quarterly 52 (3):295-314.
    We introduce a new simple way of defining the forcing method that works well in the usual setting under FA, the Foundation Axiom, and moreover works even under Aczel's AFA, the Anti-Foundation Axiom. This new way allows us to have an intuition about what happens in defining the forcing relation. The main tool is H. Friedman's method of defining the extensional membership relation ∈ by means of the intensional membership relation ε .Analogously to the usual forcing and the usual generic (...)
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  • Realization of constructive set theory into explicit mathematics: a lower bound for impredicative Mahlo universe.Sergei Tupailo - 2003 - Annals of Pure and Applied Logic 120 (1-3):165-196.
    We define a realizability interpretation of Aczel's Constructive Set Theory CZF into Explicit Mathematics. The final results are that CZF extended by Mahlo principles is realizable in corresponding extensions of T 0 , thus providing relative lower bounds for the proof-theoretic strength of the latter.
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  • (2 other versions)Realization of analysis into explicit mathematics.Sergei Tupailo - 2001 - Journal of Symbolic Logic 66 (4):1848-1864.
    We define a novel interpretation R of second order arithmetic into Explicit Mathematics. As a difference from standard D-interpretation, which was used before and was shown to interpret only subsystems proof-theoretically weaker than T 0 , our interpretation can reach the full strength of T 0 . The R-interpretation is an adaptation of Kleene's recursive realizability, and is applicable only to intuitionistic theories.
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  • The consistency of classical set theory relative to a set theory with intuitionistic logic.Harvey Friedman - 1973 - Journal of Symbolic Logic 38 (2):315-319.
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  • (4 other versions)The theory of functions and classes. Part II.L. Gordeev - 1988 - Annals of Pure and Applied Logic 38 (1):78.
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  • (1 other version)Foundations of Constructive Mathematics.Michael J. Beeson - 1987 - Studia Logica 46 (4):398-399.
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  • The Type Theoretic Interpretation of Constructive Set Theory.Peter Aczel, Angus Macintyre, Leszek Pacholski & Jeff Paris - 1984 - Journal of Symbolic Logic 49 (1):313-314.
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  • A Language and Axioms for Explicit Mathematics.Solomon Feferman, J. N. Crossley, Maurice Boffa, Dirk van Dalen & Kenneth Mcaloon - 1984 - Journal of Symbolic Logic 49 (1):308-311.
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  • (1 other version)Explicit mathematics and operational set theory: Some ontological comparisons.Gerhard Jäger & Rico Zumbrunnen - 2017 - Association for Symbolic Logic: The Bulletin of Symbolic Logic.
    We discuss several ontological properties of explicit mathematics and operational set theory: global choice, decidable classes, totality and extensionality of operations, function spaces, class and set formation via formulas that contain the definedness predicate and applications.
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  • The strength of extensionality II—weak weak set theories without infinity.Kentaro Sato - 2011 - Annals of Pure and Applied Logic 162 (8):579-646.
    By obtaining several new results on Cook-style two-sorted bounded arithmetic, this paper measures the strengths of the axiom of extensionality and of other weak fundamental set-theoretic axioms in the absence of the axiom of infinity, following the author’s previous work [K. Sato, The strength of extensionality I — weak weak set theories with infinity, Annals of Pure and Applied Logic 157 234–268] which measures them in the presence. These investigations provide a uniform framework in which three different kinds of reverse (...)
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  • Admissible sets and structures: an approach to definability theory.Jon Barwise - 1975 - New York: Springer Verlag.
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  • (1 other version)Some theories with positive induction of ordinal strength ϕω.Gerhard Jäger & Thomas Strahm - 1996 - Journal of Symbolic Logic 61 (3):818-842.
    This paper deals with: (i) the theory ID # 1 which results from $\widehat{\mathrm{ID}}_1$ by restricting induction on the natural numbers to formulas which are positive in the fixed point constants, (ii) the theory BON(μ) plus various forms of positive induction, and (iii) a subtheory of Peano arithmetic with ordinals in which induction on the natural numbers is restricted to formulas which are Σ in the ordinals. We show that these systems have proof-theoretic strength φω 0.
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  • A well-ordering proof for Feferman's theoryT 0.Gerhard Jäger - 1983 - Archive for Mathematical Logic 23 (1):65-77.
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  • (1 other version)Explicit mathematics and operational set theory: Some ontological comparisons.Gerhard Jäger & Rico Zumbrunnen - 2014 - Bulletin of Symbolic Logic 20 (3):275-292.
    We discuss several ontological properties of explicit mathematics and operational set theory: global choice, decidable classes, totality and extensionality of operations, function spaces, class and set formation via formulas that contain the definedness predicate and applications.
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  • Extending constructive operational set theory by impredicative principles.Andrea Cantini - 2011 - Mathematical Logic Quarterly 57 (3):299-322.
    We study constructive set theories, which deal with operations applying both to sets and operations themselves. Our starting point is a fully explicit, finitely axiomatized system ESTE of constructive sets and operations, which was shown in 10 to be as strong as PA. In this paper we consider extensions with operations, which internally represent description operators, unbounded set quantifiers and local fixed point operators. We investigate the proof theoretic strength of the resulting systems, which turn out to be impredicative . (...)
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  • Logic and structure.D. van Dalen - 1980 - New York: Springer Verlag.
    From the reviews: "A good textbook can improve a lecture course enormously, especially when the material of the lecture includes many technical details. Van Dalen's book, the success and popularity of which may be suspected from this steady interest in it, contains a thorough introduction to elementary classical logic in a relaxed way, suitable for mathematics students who just want to get to know logic. The presentation always points out the connections of logic to other parts of mathematics. The reader (...)
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  • Fixed points in Peano arithmetic with ordinals.Gerhard Jäger - 1993 - Annals of Pure and Applied Logic 60 (2):119-132.
    Jäger, G., Fixed points in Peano arithmetic with ordinals, Annals of Pure and Applied Logic 60 119-132. This paper deals with some proof-theoretic aspects of fixed point theories over Peano arithmetic with ordinals. It studies three such theories which differ in the principles which are available for induction on the natural numbers and ordinals. The main result states that there is a natural theory in this framework which is a conservative extension of Peano arithmeti.
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  • (1 other version)Basic proof theory.A. S. Troelstra - 2000 - New York: Cambridge University Press. Edited by Helmut Schwichtenberg.
    This introduction to the basic ideas of structural proof theory contains a thorough discussion and comparison of various types of formalization of first-order logic. Examples are given of several areas of application, namely: the metamathematics of pure first-order logic (intuitionistic as well as classical); the theory of logic programming; category theory; modal logic; linear logic; first-order arithmetic and second-order logic. In each case the aim is to illustrate the methods in relatively simple situations and then apply them elsewhere in much (...)
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  • Principles of continuous choice and continuity of functions in formal systems for constructive mathematics.Michael J. Beeson - 1977 - Annals of Mathematical Logic 12 (3):249.
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  • Subsystems of Second Order Arithmetic.Stephen George Simpson - 1998 - Springer Verlag.
    Stephen George Simpson. with definition 1.2.3 and the discussion following it. For example, taking 90(n) to be the formula n §E Y, we have an instance of comprehension, VYEIXVn(n€X<—>n¢Y), asserting that for any given set Y there exists a ...
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  • The strength of extensionality I—weak weak set theories with infinity.Kentaro Sato - 2009 - Annals of Pure and Applied Logic 157 (2-3):234-268.
    We measure, in the presence of the axiom of infinity, the proof-theoretic strength of the axioms of set theory which make the theory look really like a “theory of sets”, namely, the axiom of extensionality Ext, separation axioms and the axiom of regularity Reg . We first introduce a weak weak set theory as a base over which to clarify the strength of these axioms. We then prove the following results about proof-theoretic ordinals:1. and ,2. and . We also show (...)
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  • Theories for admissible sets: a unifying approach to proof theory.Gerhard Jäger - 1986 - Napoli: Bibliopolis.
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  • (1 other version)A Version of Kripke‐Platek Set Theory Which is Conservative Over Peano Arithmetic.Gerhard Jäger - 1984 - Mathematical Logic Quarterly 30 (1-6):3-9.
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  • Proof-theoretical analysis: weak systems of functions and classes.L. Gordeev - 1988 - Annals of Pure and Applied Logic 38 (1):1-121.
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