Zermelo'splurist Conception of Axiomatic Set Theory
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The Iterative Conception of Set Author(S): George Boolos Reviewed Work(S): Source: the Journal of Philosophy, Vol
Journal of Philosophy, Inc. The Iterative Conception of Set Author(s): George Boolos Reviewed work(s): Source: The Journal of Philosophy, Vol. 68, No. 8, Philosophy of Logic and Mathematics (Apr. 22, 1971), pp. 215-231 Published by: Journal of Philosophy, Inc. Stable URL: http://www.jstor.org/stable/2025204 . Accessed: 12/01/2013 10:53 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Journal of Philosophy, Inc. is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Philosophy. http://www.jstor.org This content downloaded on Sat, 12 Jan 2013 10:53:17 AM All use subject to JSTOR Terms and Conditions THE JOURNALOF PHILOSOPHY VOLUME LXVIII, NO. 8, APRIL 22, I97I _ ~ ~~~~~~- ~ '- ' THE ITERATIVE CONCEPTION OF SET A SET, accordingto Cantor,is "any collection.., intoa whole of definite,well-distinguished objects... of our intuitionor thought.'1Cantor alo sdefineda set as a "many, whichcan be thoughtof as one, i.e., a totalityof definiteelements that can be combinedinto a whole by a law.'2 One mightobject to the firstdefi- nitionon the groundsthat it uses the conceptsof collectionand whole, which are notionsno betterunderstood than that of set,that there ought to be sets of objects that are not objects of our thought,that 'intuition'is a termladen with a theoryof knowledgethat no one should believe, that any object is "definite,"that there should be sets of ill-distinguishedobjects, such as waves and trains,etc., etc. -
Elements of Set Theory
Elements of set theory April 1, 2014 ii Contents 1 Zermelo{Fraenkel axiomatization 1 1.1 Historical context . 1 1.2 The language of the theory . 3 1.3 The most basic axioms . 4 1.4 Axiom of Infinity . 4 1.5 Axiom schema of Comprehension . 5 1.6 Functions . 6 1.7 Axiom of Choice . 7 1.8 Axiom schema of Replacement . 9 1.9 Axiom of Regularity . 9 2 Basic notions 11 2.1 Transitive sets . 11 2.2 Von Neumann's natural numbers . 11 2.3 Finite and infinite sets . 15 2.4 Cardinality . 17 2.5 Countable and uncountable sets . 19 3 Ordinals 21 3.1 Basic definitions . 21 3.2 Transfinite induction and recursion . 25 3.3 Applications with choice . 26 3.4 Applications without choice . 29 3.5 Cardinal numbers . 31 4 Descriptive set theory 35 4.1 Rational and real numbers . 35 4.2 Topological spaces . 37 4.3 Polish spaces . 39 4.4 Borel sets . 43 4.5 Analytic sets . 46 4.6 Lebesgue's mistake . 48 iii iv CONTENTS 5 Formal logic 51 5.1 Propositional logic . 51 5.1.1 Propositional logic: syntax . 51 5.1.2 Propositional logic: semantics . 52 5.1.3 Propositional logic: completeness . 53 5.2 First order logic . 56 5.2.1 First order logic: syntax . 56 5.2.2 First order logic: semantics . 59 5.2.3 Completeness theorem . 60 6 Model theory 67 6.1 Basic notions . 67 6.2 Ultraproducts and nonstandard analysis . 68 6.3 Quantifier elimination and the real closed fields . -
Constructive Zermelo-Fraenkel Set Theory, Power Set, and the Calculus of Constructions
This is a repository copy of Constructive zermelo-fraenkel set theory, power set, and the calculus of constructions. White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/75182/ Book Section: Rathjen, M (2012) Constructive zermelo-fraenkel set theory, power set, and the calculus of constructions. In: Dybjer, P, Lindström, S, Palmgren, E and Sundholm, G, (eds.) Epistemology versus ontology: Essays on the philosophy and foundations of mathematics in honour of Per Martin-Löf. Logic, Epistemology, and the Unity of Science, 27 . Springer , Dordrecht, Netherlands , 313 - 349. ISBN 9789400744356 https://doi.org/10.1007/978-94-007-4435-6 Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version - refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher’s website. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ Constructive Zermelo-Fraenkel Set Theory, Power Set, and the Calculus of Constructions Michael Rathjen∗ Department of Pure Mathematics, University of Leeds Leeds LS2 9JT, United Kingdom [email protected] May 4, 2012 Abstract Full intuitionistic Zermelo-Fraenkel set theory, IZF, is obtained from constructive Zermelo- Fraenkel set theory, CZF, by adding the full separation axiom scheme and the power set axiom. -
Constructive Set Theory and Brouwerian Principles1
Constructive Set Theory and Brouwerian Principles1 Michael Rathjen (Department of Mathematics, The Ohio State University,2 Email: [email protected]) Abstract: The paper furnishes realizability models of constructive Zermelo-Fraenkel set theory, CZF, which also validate Brouwerian principles such as the axiom of con- tinuous choice (CC), the fan theorem (FT), and monotone bar induction (BIM), and thereby determines the proof-theoretic strength of CZF augmented by these principles. The upshot is that CZF+CC+FT possesses the same strength as CZF, or more pre- 0 cisely, that CZF+CC+FT is conservative over CZF for Π2 statements of arithmetic, whereas the addition of a restricted version of bar induction to CZF (called decidable bar induction, BID) leads to greater proof-theoretic strength in that CZF+BID proves the consistency of CZF. Key Words: Constructive set theory, Brouwerian principles, partial combinatory al- gebra, realizability Category: F.4.1 1 Introduction Constructive Zermelo-Fraenkel Set Theory has emerged as a standard reference theory that relates to constructive predicative mathematics as ZFC relates to classical Cantorian mathematics. The general topic of Constructive Set Theory originated in the seminal 1975 paper of John Myhill (cf. [16]), where a specific ax- iom system CST was introduced. Myhill developed constructive set theory with the aim of isolating the principles underlying Bishop's conception of what sets and functions are. Moreover, he wanted \these principles to be such as to make the process of formalization completely trivial, as it is in the classical case" ([16], p. 347). Indeed, while he uses other primitives in his set theory CST besides the notion of set, it can be viewed as a subsystem of ZF. -
LONG BOREL GAMES 3 Large Cardinal Axioms, Or Strengthenings of the Axiom of Infinity, and Use Them to Prove the Determinacy of Games on the Natural Numbers
LONG BOREL GAMES J. P. AGUILERA Abstract. We study games of length ω2 with moves in N and Borel payoff. These are, e.g., games in which two players alternate turns playing digits to produce a real number in [0, 1] infinitely many times, after which the winner is decided in terms of the sequence belonging to a Borel set in the product space [0, 1]N. The main theorem is that Borel games of length ω2 are determined if, and only if, for every countable ordinal α, there is a fine-structural, countably iterable model of Zermelo set theory with α-many iterated powersets above a limit of Woodin cardinals. Contents 1. Introduction 1 2. Preliminaries 5 3. Determinacy and L(R) 7 4. Proof of Lemma 3.1 18 5. Derived model theorems 25 References 28 1. Introduction Given a Borel subset A of the Hilbert space ℓ2, define a two-player perfect- information, zero-sum game in which Player I and Player II alternate turns playing 0 digits xi ∈{0, 1,..., 9} infinitely often, giving rise to a real number ∞ x0 x0 = i . X 10i+1 i=0 arXiv:1906.11757v1 [math.LO] 27 Jun 2019 Afterwards, they continue alternating turns to produce real numbers x1, x2, and so on. To ensure that the sequence belongs to ℓ2, we normalize, e.g., by setting xi yi = . i +1 Player I wins the game if, and only if, ~y ∈ A; otherwise Player II wins. These are games of transfinite length ω2. (Recall that ω denotes the order-type of the natural numbers.) It is a natural question whether these games are determined, i.e., whether one of the players has a winning strategy. -
Undergraduate Logic Sequence: the Notes
Undergraduate logic sequence: the notes November 4, 2015 ii Contents 1 Zermelo{Fraenkel set theory 1 1.1 Historical context . 1 1.2 The language of the theory . 3 1.3 The most basic axioms . 4 1.4 Axiom schema of Comprehension . 6 1.5 Relations and functions . 7 1.6 Axiom of Infinity . 9 1.7 Axiom of Choice . 10 1.8 Axiom schema of Replacement . 11 1.9 Axiom of Regularity . 12 2 Numbers, Ordinals, and Cardinals 15 2.1 Von Neumann's natural numbers . 15 2.2 Finite and infinite sets . 18 2.3 Inductive and Recursive Definability . 21 2.4 Models of Set Theory . 24 2.5 The Hereditarily Finite Sets . 26 2.6 Cardinality . 28 2.7 Countable and uncountable sets . 31 3 The transfinite 35 3.1 Ordinals . 35 3.2 Transfinite induction and recursion . 38 3.3 Ordinal Arithmetic . 44 3.4 Ordinals and Well-Orderings . 49 3.5 Equivalent versions of the Axiom of Choice . 51 3.6 Applications of choice . 53 3.7 Cardinal numbers . 55 3.8 Models of Set Theory, Revisited . 57 4 Descriptive set theory 59 4.1 Rational and real numbers . 59 4.2 Topological spaces . 61 4.3 Polish spaces . 64 iii iv CONTENTS 4.4 Universality theorems . 67 4.5 Borel sets . 69 4.6 Analytic sets . 72 4.7 Lebesgue's mistake . 74 4.8 Suslin's fix . 76 5 First order logic 79 5.1 Propositional logic . 79 5.2 Syntax . 84 5.3 Semantics . 87 5.4 Completeness theorem . 88 Chapter 1 Zermelo{Fraenkel set theory 1.1 Historical context In 19th century, mathematicians produced a great number of sophisticated the- orems and proofs. -
The Axiom of Choice and Its Implications in Mathematics
Treball final de grau GRAU DE MATEMATIQUES` Facultat de Matem`atiquesi Inform`atica Universitat de Barcelona The Axiom of Choice and its implications in mathematics Autor: Gina Garcia Tarrach Director: Dr. Joan Bagaria Realitzat a: Departament de Matem`atiques i Inform`atica Barcelona, 29 de juny de 2017 Abstract The Axiom of Choice is an axiom of set theory which states that, given a collection of non-empty sets, it is possible to choose an element out of each set of the collection. The implications of the acceptance of the Axiom are many, some of them essential to the de- velopment of contemporary mathematics. In this work, we give a basic presentation of the Axiom and its consequences: we study the Axiom of Choice as well as some of its equivalent forms such as the Well Ordering Theorem and Zorn's Lemma, some weaker choice principles, the implications of the Axiom in different fields of mathematics, so- me paradoxical results implied by it, and its role within the Zermelo-Fraenkel axiomatic theory. i Contents Introduction 1 0 Some preliminary notes on well-orders, ordinal and cardinal numbers 3 1 Historical background 6 2 The Axiom of Choice and its Equivalent Forms 9 2.1 The Axiom of Choice . 9 2.2 The Well Ordering Theorem . 10 2.3 Zorn's Lemma . 12 2.4 Other equivalent forms . 13 3 Weaker Forms of the Axiom of Choice 14 3.1 The Axiom of Dependent Choice . 14 3.2 The Axiom of Countable Choice . 15 3.3 The Boolean Prime Ideal Theorem . -
Basic Set Theory
Basic set theory Richard Pettigrew January 26, 2012 1 A set and its members • A set is a collection of objects. • The objects in a set are called its elements or members. • If x is a set and z is a member of x, then we write z 2 x. • If x is a set and z is not a member of x, then we write z 62 x. • If x and y are sets and if all members of x are also members of y, then we say that x is a subset of y. We write this x ⊆ y. Thus, we have: x ⊆ y $ 8z(z 2 x ! z 2 y) • The members of a set determine that set. That is, there are no two distinct sets with the same members. This distinguishes sets from properties, concepts, and other intensional notions. This is codified in the following axiom of set theory: Axiom 1 (Axiom of Extensionality) 8x8y[x = y $ (8z)(z 2 x $ z 2 y)] Another way of stating this is that if x ⊆ y and y ⊆ x, then x = y. This axiom is reasonably uncontroversial and it is shared by nearly all versions of set theory. 2 Which sets are there? 2.1 Na¨ıve set theory Na¨ıveSet Theory has two axioms: • The Axiom of Extensionality. • The Axiom of Unrestricted Comprehension. This says that, for any property, there is a set of all and only those things that have that property. More precisely, we restrict to properties that can be defined by formulae in the language of set theory with parameters: 1 Axiom 2 (Axiom of Unrestricted Comprehension) Given a formula Φ(x; w1; : : : ; wn) in the language of set theory, 8w1; : : : ; wn9x8z[z 2 x $ Φ(z; w1; : : : ; wn)] Given a formula Φ(x; w1; : : : ; wn) and values w1, :::, wn, we write this set fx : Φ(x; w1; : : : ; wn)g. -
Pro and Contra Hilbert: Zermelo's Set Theories∗ Volker Peckhaus 1
Pro and Contra Hilbert: Zermelo’s Set Theories¤ Volker Peckhaus Universit¨atPaderborn Fakult¨atf¨urKulturwissenschaften – Philosophie Warburger Str. 100, D – 33098 Paderborn E-mail: [email protected] 1 Introduction On 27 July 1941 Ernst Zermelo celebrated his 70th birthday. On this occa- sion he received congratulations from Paul Bernays, his former student and collaborator, who was at that time Privatdozent at the Eidgen¨ossische Tech- nische Hochschule in Zurich. In his response, dated 1 October 1941, Zermelo wrote the following: I’m very glad about the fact that still some of my former colleagues and collaborators remember me, while I have lost several of my friends by death. One just becomes more and more lonely, is therefore the more grateful for any friendly remembrance. [ . ] Of course, I have no illusions anymore about the effects of my essential life’s work as it concerns “foundations” and set theory. As far as my name is mentioned at all, this is always done only in respect to the “principle of choice” for which I never claimed priority.1 As evidence Zermelo referred to a recent congress on foundations at Zurich, most likely the congress “Les fondements et la m´ethode des sciences math´ema- tiques” in December 1938 (cf. Gonseth 1941 ), where none of his papers pub- lished after 1904, namely both notes in the Annalen der Mathematik of 1908 and both papers published in the Fundamenta Mathematicae in 1930 and 1935, had been mentioned, as he observed, whereas “the dubious merits of a Skolem or G¨odelwere spinned out pretty much.” In this letter, Zermelo also remembered the convention of the Deutsche Mathematiker-Vereinigung ¤I would like to thank Christian Thiel (Erlangen), Heinz-Dieter Ebbinghaus (Freiburg i. -
Slim Models of Zermelo Set Theory
Slim models of Zermelo set theory A.R.D.Mathias Universidad de los Andes, Santa F´e de Bogot´a Abstract Working in Z +KP , we give a new proof that the class of hereditarily finite sets cannot be proved to be a set in Zermelo set theory, extend the method to establish other failures of replacement, and exhibit a formula Φ(λ, a) such that for any sequence hAλ j λ a limit ordinal i λ where for each λ, Aλ ⊆ 2, there is a supertransitive inner model of Zermelo containing all ordinals in which for every λ Aλ = fa j Φ(λ, a)g. Preliminaries This paper explores the weakness of Zermelo set theory, Z, as a vehicle for recursive definitions. We work in the system Z +KP , which adds to the axioms of Zermelo those of Kripke{Platek set theory KP . Z + KP is of course a subsystem of the familiar system ZF of Zermelo{Fraenkel. Mention is made of the axiom of choice, but our constructions do not rely on that Axiom. It is known that Z +KP +AC is consistent relative to Z: see [M2], to appear as [M3], which describes inter alia a method of extending models of Z + AC to models of Z + AC + KP . We begin by reviewing the axioms of the two systems Z and KP . In the formulation of KP , we shall use the familiar L´evy classification of formulæ: ∆0 formulæ are those in which every quantifier is restricted, 8x(x 2 y =) : : :) or 9x(x 2 y & : : :), which we write as 8x:2y : : : and 9x:2y : : : respectively. -
Lambda-Z: Zermelo's Set Theory As a PTS with 4 Sorts
Lambda-Z: Zermelo’s Set Theory as a PTS with 4 Sorts Alexandre Miquel To cite this version: Alexandre Miquel. Lambda-Z: Zermelo’s Set Theory as a PTS with 4 Sorts. TYPES’04, 2006, Jouy- en-Josas, France. pp.232-251. hal-00150886 HAL Id: hal-00150886 https://hal.archives-ouvertes.fr/hal-00150886 Submitted on 3 Jun 2007 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. λZ: Zermelo’s Set Theory as a PTS with 4 Sorts Alexandre Miquel PPS & Universit´eParis 7 175 rue du Chevaleret, 75013 Paris Abstract. We introduce a pure type system (PTS) λZ with four sorts and show that this PTS captures the proof-theoretic strength of Zer- melo’s set theory. For that, we show that the embedding of the language of set theory into λZ via the ‘sets as pointed graphs’ translation makes λZ a conservative extension of IZ + AFA + TC (intuitionistic Zermelo’s set theory plus Aczel’s antifoundation axiom plus the axiom of transitive closure)—a theory which is equiconsistent to Zermelo’s. The proof of con- servativity is achieved by defining a retraction from λZ to a (skolemised version of) Zermelo’s set theory and by showing that both transforma- tions commute via the axioms AFA and TC. -
Choice Principles in Constructive and Classical Set Theories
Choice principles in constructive and classical set theories Michael Rathjen∗ Department of Pure Mathematics, University of Leeds Leeds LS2 9JT, United Kingdom E-Mail: [email protected] Abstract The objective of this paper is to assay several forms of the axiom of choice that have been deemed constructive. In addition to their deductive relation- ships, the paper will be concerned with metamathematical properties effected by these choice principles and also with some of their classical models. 1 Introduction Among the axioms of set theory, the axiom of choice is distinguished by the fact that it is the only one that one finds ever mentioned in workaday mathematics. In the mathematical world of the beginning of the 20th century, discussions about the status of the axiom of choice were important. In 1904 Zermelo proved that every set can be well-ordered by employing the axiom of choice. While Zermelo argued that it was self-evident, it was also criticized as an excessively non-constructive principle by some of the most distinguished analysts of the day. At the end of a note sent to the Mathematische Annalen in December 1905, Borel writes about the axiom of choice: It seems to me that the objection against it is also valid for every reason- ing where one assumes an arbitrary choice made an uncountable number of times, for such reasoning does not belong in mathematics. ([10], pp. 1251-1252; translation by H. Jervell, cf. [22], p. 96.) Borel canvassed opinions of the most prominent French mathematicians of his gen- eration - Hadamard, Baire, and Lebesgue - with the upshot that Hadamard sided with Zermelo whereas Baire and Lebesgue seconded Borel.