On Quine's Set Theory
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Nonstandard Set Theories and Information Management
Nonstandard Set Theories and Information Management VAROL AKMAN akmantroycsbilkentedutr Department of Computer Engineering and Information Science Bilkent University Bilkent Ankara Turkey MUJDATPAKKAN pakkantrb ounbitnet Department of Computer Engineering Bosphorus University Bebek Istanbul Turkey Abstract The merits of set theory as a foundational to ol in mathematics stimulate its use in various areas of articial intelligence in particular intelligent information systems In this pap er a study of various nonstandard treatments of set theory from this p ersp ective is oered Applications of these alternative set theories to information or knowledge management are surveyed Keywords set theory knowledge representation information management commonsense rea soning nonwellfounded sets hyp ersets Intro duction Set theory is a branch of mo dern mathematics with a unique place b ecause various other branches can b e formally dened within it For example Book of the inuential works of N Bourbaki is devoted to the theory of sets and provides the framework for the remaining 1 volumes Bourbaki said in Goldblatt All mathematical theories may b e regarded as extensions of the general theory of sets On these foundations I can state that I can build up the whole of the mathematics of the present day This brings up the p ossibility of using set theory in foundational studies in AI Mc Carthy has emphasized the need for fundamental research in AI and claimed that AI needs mathematical and logical theory involving conceptual innovations In an -
Lecture Notes: Axiomatic Set Theory
Lecture Notes: Axiomatic Set Theory Asaf Karagila Last Update: May 14, 2018 Contents 1 Introduction 3 1.1 Why do we need axioms?...............................3 1.2 Classes and sets.....................................4 1.3 The axioms of set theory................................5 2 Ordinals, recursion and induction7 2.1 Ordinals.........................................8 2.2 Transfinite induction and recursion..........................9 2.3 Transitive classes.................................... 10 3 The relative consistency of the Axiom of Foundation 12 4 Cardinals and their arithmetic 15 4.1 The definition of cardinals............................... 15 4.2 The Aleph numbers.................................. 17 4.3 Finiteness........................................ 18 5 Absoluteness and reflection 21 5.1 Absoluteness...................................... 21 5.2 Reflection........................................ 23 6 The Axiom of Choice 25 6.1 The Axiom of Choice.................................. 25 6.2 Weak version of the Axiom of Choice......................... 27 7 Sets of Ordinals 31 7.1 Cofinality........................................ 31 7.2 Some cardinal arithmetic............................... 32 7.3 Clubs and stationary sets............................... 33 7.4 The Club filter..................................... 35 8 Inner models of ZF 37 8.1 Inner models...................................... 37 8.2 Gödel’s constructible universe............................. 39 1 8.3 The properties of L ................................... 41 8.4 Ordinal definable sets................................. 42 9 Some combinatorics on ω1 43 9.1 Aronszajn trees..................................... 43 9.2 Diamond and Suslin trees............................... 44 10 Coda: Games and determinacy 46 2 Chapter 1 Introduction 1.1 Why do we need axioms? In modern mathematics, axioms are given to define an object. The axioms of a group define the notion of a group, the axioms of a Banach space define what it means for something to be a Banach space. -
The Bristol Model (5/5)
The Bristol model (5/5) Asaf Karagila University of East Anglia 22 November 2019 RIMS Set Theory Workshop 2019 Set Theory and Infinity Asaf Karagila (UEA) The Bristol model (5/5) 22 November 2019 1 / 23 Review Bird’s eye view of Bristol We started in L by choosing a Bristol sequence, that is a sequence of permutable families and permutable scales, and we constructed one step at a time models, Mα, such that: 1 M0 = L. Mα Mα+1 2 Mα+1 is a symmetric extension of Mα, and Vω+α = Vω+α . 3 For limit α, Mα is the finite support limit of the iteration, and Mα S Mβ Vω+α = β<α Vω+β. By choosing our Mα-generic filters correctly, we ensured that Mα ⊆ L[%0], where %0 was an L-generic Cohen real. We then defined M, the Bristol model, S S Mα as α∈Ord Mα = α∈Ord Vω+α. Asaf Karagila (UEA) The Bristol model (5/5) 22 November 2019 2 / 23 Properties of the Bristol model Small Violations of Choice Definition (Blass) We say that V |= SVC(X) if for every A there is an ordinal η and a surjection f : X × η → A. We write SVC to mean ∃X SVC(X). Theorem If M = V (x) where V |= ZFC, then M |= SVC. Theorem If M is a symmetric extension of V |= ZFC, Then M |= SVC. The following are equivalent: 1 SVC. 2 1 ∃X such that X<ω AC. 3 ∃P such that 1 P AC. 4 V is a symmetric extension of a model of ZFC (Usuba). -
On the Origins of Bisimulation and Coinduction
On the Origins of Bisimulation and Coinduction DAVIDE SANGIORGI University of Bologna, Italy The origins of bisimulation and bisimilarity are examined, in the three fields where they have been independently discovered: Computer Science, Philosophical Logic (precisely, Modal Logic), Set Theory. Bisimulation and bisimilarity are coinductive notions, and as such are intimately related to fixed points, in particular greatest fixed points. Therefore also the appearance of coinduction and fixed points is discussed, though in this case only within Computer Science. The paper ends with some historical remarks on the main fixed-point theorems (such as Knaster-Tarski) that underpin the fixed-point theory presented. Categories and Subject Descriptors: F.4.1 [Mathematical logic and formal languages]: Math- ematical Logic—Computational logic; Modal logic; Set theory; F.4.0 [Mathematical logic and formal languages]: General General Terms: Theory, Verification Additional Key Words and Phrases: Bisimulation, coinduction, fixed points, greatest fixed points, history Contents 1 Introduction 112 2 Background 114 2.1 Bisimulation................................ 114 2.2 Approximants of bisimilarity . 116 2.3 Coinduction................................116 3 Bisimulation in Modal Logic 119 3.1 Modallogics................................119 3.2 Fromhomomorphismtop-morphism . 120 3.3 JohanvanBenthem ........................... 122 3.4 Discussion.................................125 4 Bisimulation in Computer Science 125 4.1 Algebraictheoryofautomata . 125 4.2 RobinMilner ...............................128 Author’s address: Dipartimento di Scienze dell’Informazione Universita’ di Bologna Mura Anteo Zamboni, 7 40126 Bologna, ITALY. Permission to make digital/hard copy of all or part of this material without fee for personal or classroom use provided that the copies are not made or distributed for profit or commercial advantage, the ACM copyright/server notice, the title of the publication, and its date appear, and notice is given that copying is by permission of the ACM, Inc. -
New Foundations of Cost–Benefit Analysis
Regulation & Governance (2009) 3, 72–83 doi:10.1111/j.1748-5991.2009.01045.x RESEARCH FORUM New foundations of cost–benefit analysis A reply to Professors Sinden, Kysar, and Driesen Matthew Adler University of Pennsylvania Law School, Philadelphia, PA, USA Eric A. Posner University of Chicago Law School, Chicago, IL, USA Abstract This article responds to the criticisms of New Foundations of Cost–Benefit Analysis that appeared in a review by Amy Sinden, Douglas A. Kysar, and David M. Driesen. We argue that their criticisms are either based on misunderstandings of our approach or are too demanding, in the sense that no reasonable decision procedure would satisfy them. We illustrate this second argument by demon- strating that their preferred approach – feasibility analysis – has little to recommend it. Keywords: cost–benefit analysis, regulation, welfarism. Introduction The basic thrust of New Foundations of Cost–Benefit Analysis is to detach cost–benefit analysis (CBA) from Kaldor–Hicks efficiency,which we argue lacks moral relevance (Adler & Posner 2006, pp. 19–24), and instead to see CBA as a rough, administrable proxy for overall wellbeing. We defend the moral relevance of overall wellbeing by appealing, not to utilitarianism,but to“weak welfarism”– a much more catholic moral view that sees overall wellbeing as one among a possible plurality of foundational moral criteria, along with distributive considerations, deontological rights, and non-welfare values (Adler & Posner 2006, pp. 52–61). We also reject the simple equation of wellbeing and preference- satisfaction. An outcome benefits a person only if she prefers it and her preferences are self-interested and survive idealization (Adler & Posner 2006, pp. -
On the Brink of New Promise the FUTURE of U.S
On the Brink of New Promise THE FUTURE OF U.S. COMMUNITY FOUNDATIONS By Lucy Bernholz, Katherine Fulton, and Gabriel Kasper Blueprint Research & Design, Inc. and the Monitor Institute, a member of Monitor Group Created with funding support from the Charles Stewart Mott Foundation and the Ford Foundation © Copyright 2005 Blueprint Research & Design, Inc. and Monitor Company Group, LLP. We encourage readers to use and share the contents of this report, with the understanding that it is the intellectual property of Blueprint Research & Design and the Monitor Group, and that full attribution is required. An invitation from the Charles Stewart Mott and Ford foundations Our two foundations have been privileged to have worked with community foundations across the United States over the past quarter century. For both of us, this is an area of philanthropy we care about deeply. Th e Charles Stewart Mott and Ford foundations work at national and indeed international levels. Yet we both know how valuable it is for large private foundations to have strong, dynamic community founda- tions as partners working at the local level. Th is is why we embraced the opportunity to look deep into the future of the fi eld through the expert eyes of Lucy Bernholz, Katherine Fulton, and Gabriel Kasper. Over those years, Mott and Ford have made grants to community foundations to build general and administrative endowments, to provide peer-to-peer learning opportunities and technical assistance, and to strengthen programming expertise in areas such as low-income neighborhoods, the environment, and minority communities. We have also assisted the fi eld to develop abroad, and we have helped build the infrastructure for community foundations We recommend this report to community foundation staff, boards of directors, across the nation. -
Forcing and the Universe of Sets: Must We Lose Insight?
Forcing and the Universe of Sets: Must we lose insight? Neil Barton∗ 29 January 2018y Abstract A central area of current philosophical debate in the foundations of mathe- matics concerns whether or not there is a single, maximal, universe of set theory. Universists maintain that there is such a universe, while Multiversists argue that there are many universes, no one of which is ontologically privileged. Often forc- ing constructions that add subsets to models are cited as evidence in favour of the latter. This paper informs this debate by analysing ways the Universist might interpret this discourse that seems to necessitate the addition of subsets to V . We argue that despite the prima facie incoherence of such talk for the Universist, she nonetheless has reason to try and provide interpretation of this discourse. We analyse extant interpretations of such talk, and argue that while tradeoffs in nat- urality have to be made, they are not too severe. Introduction Recent discussions of the philosophy of set theory have often focussed on how many universes of sets there are. The following is a standard position: Universism. There is a unique, maximal, proper class sized universe containing all the sets (denoted by ‘V ’). Universism has often been thought of as the ‘default’ position on the ontology of sets.1 However, some have seen the existence of many different epistemic pos- sibilities for the nature of the set-theoretic universe, shown by the large diversity of model-theoretic constructions witnessing independence (we discuss two of these methods later) as indicative of the existence of a diversity of different set-theoretic universes. -
The Problem of the Consistency of “New Foundations”
The Problem of the Consistency of \New Foundations" Randall Holmes September 10, 2013 1 Abstract: I will explain the nature of the long- standing problem of the consistency of the set theory New Foundations proposed by the philoso- pher W. v. O. Quine in 1937 both in the prior context of the development of set theory, its usefulness in mathematics, and the problem of the "paradoxes" of set theory, and in the pos- terior context of partial solutions to the consis- tency problem and related results. I do claim to have solved this problem (this is not generally agreed yet) but I am not going to talk about that on this occasion. The talk should be ac- cessible to a general audience of mathemati- cians; I hope that a graduate student or mature undergraduate would get something out of it too. Plan of the talk I'm going to talk about the problem of the consistency of Quine's set theory \New Foun- dations", which is the central issue of my tiny area of set theory. I currently believe that I have solved this prob- lem, but this has nothing to do with the present talk, or very little. What I propose to do is explain what the prob- lem is and put it in some kind of context. Why does one need a set theory? Why is there a problem of consistency of set theories? What is New Foundations anyway and why is there a problem with it in particular? What are the relevant related results and partial solutions to the problem? 2 What is a set? When I tell a layman with no maths that I work in set theory, they ask \What is a set?". -
Hamkins' Analogy Between Set Theory and Geometry
TAKING THE ANALOGY BETWEEN SET THEORY AND GEOMETRY SERIOUSLY SHARON BERRY Abstract. Set theorist Joel Hamkins uses considerations about forcing argu- ments in set theory together with an analogy between set theory and geometry to motivate his influential set-theoretic multiverse program: a distinctive and powerfully truthvalue-antirealist form of plenetudinous Platonism. However, I'll argue that taking this analogy seriously cuts against Hamkins' proposal in one important way. I'll then note that putting a (hyperintensional) modal twist on Hamkins' Multiverse lets take Hamkins' analogy further and address his motivations equally well (or better) while maintaining naive realism. 1. Introduction Philosophers who want to deny that there are right answers to mathematical ques- tions (like the Continuum Hypothesis) which are undecidable via deduction from mathematical axioms we currently accept often draw on an analogy between set theory and geometry [6, 12]1. In this paper I will discuss one of the most important and interesting recent examples of this phenomenon: set theorist Joel Hamkins' use of (a specific form of) this analogy to motivate his set-theoretic multiverse program. Hamkins has developed an influential2 multiverse approach to set theory, on which there are many different hierarchies of sets, and there's no fact of the matter about whether certain set-theoretic statements are true, beyond the fact that they are true of some hierarchies of sets within the multiverse and false in others. On this view there is no `full' intended hierarchy of sets which contains all subsets of sets it contains- or even all subsets of the natural numbers. -
On the Absoluteness of $\Aleph 1 $-Freeness
ON THE ABSOLUTENESS OF ℵ1-FREENESS DANIEL HERDEN, ALEXANDRA V. PASI Abstract. ℵ1-free groups, abelian groups for which every countable subgroup is free, exhibit a number of interesting algebraic and set-theoretic properties. In this paper, we give a complete proof that the property of being ℵ1-free is absolute; that is, if an abelian group G is ℵ1-free in some transitive model M of ZFC, then it is ℵ1-free in any transitive model of ZFC containing G. The absoluteness of ℵ1-freeness has the following remarkable consequence: an abelian group G is ℵ1-free in some transitive model of ZFC if and only if it is (countable and) free in some model extension. This set-theoretic characteri- zation will be the starting point for further exploring the relationship between the set-theoretic and algebraic properties of ℵ1-free groups. In particular, this paper will demonstrate how proofs may be dramatically simplified using model extensions for ℵ1-free groups. 1. Introduction ℵ1-free groups, abelian groups whose countable subgroups are free, are the sub- ject of significant study in abelian group theory. The Baer-Specker group, the direct product of countably many copies of Z, provides a simple example of an ℵ1-free group (which is not free), [1, 14]. The class of ℵ1-free groups exhibits a high degree of algebraic complexity, as evidenced by the test of ring-realization: any ring with free additive structure can be realized as the endomorphism ring of some ℵ1-free group [4, 5]. ℵ1-free groups also play an important role in the Whitehead Problem, as ev- ery Whitehead group can be shown to be ℵ1-free [15]. -
By WV QUINE Only the Truth Functions, Quantification, and Membership
538 MATHEMATICS: W. V. QUINE PROC. N. A. S. ON THE CONSISTENC Y OF "NEW FOUNDA TIONS" By W. V. QUINE HARVARD UNIVERSITY Communicated by Hassler Whitney, June 12, 1951 The question of the consistency of the system of set theory in my "New Foundations,"' briefly NF, has long been mooted.2 3 The question takes on added interest with Wang's new revision4 of the system of my Mathe- matical Logic;5 for Wang has proved that this revision, which is to be used in the forthcoming third printing of Mathematical Logic, is consistent if NF is consistent. The purpose of the present note is to point out that NF is consistent if and only if the system of Whitehead and Russell's Principia Mathematica,6 briefly PM, is consistent in a certain one of its natural ver- sions. PM may be conceived in a form in which the variables carry indices indi- cating logical type. Alternatively PM may be conceived under a conven- tion which Whitehead and Russell called typical ambiguity; under this con- vention the indices are suppressed but still only those formulae are ad- mitted as meaningful which are stratified, i.e., so constituted that type in- dices could be inserted everywhere without violating the theory of types. Another point on which we have a choice, in framing a version of PM, is the status of relations and relational predication: we may assume relational predication as primitive on a par with set-membership, and decree a sprawling annex to the theory of types to accommodate relations, as was done in effect by Whitehead and Russell; or alternatively we may, follow- ing Wiener,7 reduce relations to certain sets of sets of sets (at the cost of giving up relations between things of different types). -
New Foundations of Transnational Private Regulation Author(S): Fabrizio Cafaggi Source: Journal of Law and Society, Vol
Cardiff University New Foundations of Transnational Private Regulation Author(s): Fabrizio Cafaggi Source: Journal of Law and Society, Vol. 38, No. 1, The Challenge of Transnational Private Regulation: Conceptual and Constitutional Debates (MARCH 2011), pp. 20-49 Published by: Wiley on behalf of Cardiff University Stable URL: https://www.jstor.org/stable/23030395 Accessed: 21-01-2019 16:18 UTC 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]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at https://about.jstor.org/terms Cardiff University, Wiley are collaborating with JSTOR to digitize, preserve and extend access to Journal of Law and Society This content downloaded from 154.59.124.94 on Mon, 21 Jan 2019 16:18:47 UTC All use subject to https://about.jstor.org/terms JOURNAL OF LAW AND SOCIETY VOLUME 38, NUMBER 1, MARCH 2011 ISSN: 0263-323X, pp. 20-49 New Foundations of Transnational Private Regulation Fabrizio Cafaggi* In section I oj this article, the factors driving towards the emergence of new transnational private regulation (TPR) are identified in com parison with, on the one hand, merchant law and, on the other, inter national public regimes. In section II, the focus is on the private sphere, looking at both the different conflicts of interests arising in the regulatory relationships and the need for governance responses.