CATEGORICAL ONTOLOGY I Contents 1. Introduction 2 2. Categories As Places 8 3. Preliminaries on Variable Set Theory 16 4. the In
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The Metamathematics of Putnam's Model-Theoretic Arguments
The Metamathematics of Putnam's Model-Theoretic Arguments Tim Button Abstract. Putnam famously attempted to use model theory to draw metaphysical conclusions. His Skolemisation argument sought to show metaphysical realists that their favourite theories have countable models. His permutation argument sought to show that they have permuted mod- els. His constructivisation argument sought to show that any empirical evidence is compatible with the Axiom of Constructibility. Here, I exam- ine the metamathematics of all three model-theoretic arguments, and I argue against Bays (2001, 2007) that Putnam is largely immune to meta- mathematical challenges. Copyright notice. This paper is due to appear in Erkenntnis. This is a pre-print, and may be subject to minor changes. The authoritative version should be obtained from Erkenntnis, once it has been published. Hilary Putnam famously attempted to use model theory to draw metaphys- ical conclusions. Specifically, he attacked metaphysical realism, a position characterised by the following credo: [T]he world consists of a fixed totality of mind-independent objects. (Putnam 1981, p. 49; cf. 1978, p. 125). Truth involves some sort of correspondence relation between words or thought-signs and external things and sets of things. (1981, p. 49; cf. 1989, p. 214) [W]hat is epistemically most justifiable to believe may nonetheless be false. (1980, p. 473; cf. 1978, p. 125) To sum up these claims, Putnam characterised metaphysical realism as an \externalist perspective" whose \favorite point of view is a God's Eye point of view" (1981, p. 49). Putnam sought to show that this externalist perspective is deeply untenable. To this end, he treated correspondence in terms of model-theoretic satisfaction. -
Topos Theory
Topos Theory Olivia Caramello Sheaves on a site Grothendieck topologies Grothendieck toposes Basic properties of Grothendieck toposes Subobject lattices Topos Theory Balancedness The epi-mono factorization Lectures 7-14: Sheaves on a site The closure operation on subobjects Monomorphisms and epimorphisms Exponentials Olivia Caramello The subobject classifier Local operators For further reading Topos Theory Sieves Olivia Caramello In order to ‘categorify’ the notion of sheaf of a topological space, Sheaves on a site Grothendieck the first step is to introduce an abstract notion of covering (of an topologies Grothendieck object by a family of arrows to it) in a category. toposes Basic properties Definition of Grothendieck toposes Subobject lattices • Given a category C and an object c 2 Ob(C), a presieve P in Balancedness C on c is a collection of arrows in C with codomain c. The epi-mono factorization The closure • Given a category C and an object c 2 Ob(C), a sieve S in C operation on subobjects on c is a collection of arrows in C with codomain c such that Monomorphisms and epimorphisms Exponentials The subobject f 2 S ) f ◦ g 2 S classifier Local operators whenever this composition makes sense. For further reading • We say that a sieve S is generated by a presieve P on an object c if it is the smallest sieve containing it, that is if it is the collection of arrows to c which factor through an arrow in P. If S is a sieve on c and h : d ! c is any arrow to c, then h∗(S) := fg | cod(g) = d; h ◦ g 2 Sg is a sieve on d. -
Starting the Dismantling of Classical Mathematics
Australasian Journal of Logic Starting the Dismantling of Classical Mathematics Ross T. Brady La Trobe University Melbourne, Australia [email protected] Dedicated to Richard Routley/Sylvan, on the occasion of the 20th anniversary of his untimely death. 1 Introduction Richard Sylvan (n´eRoutley) has been the greatest influence on my career in logic. We met at the University of New England in 1966, when I was a Master's student and he was one of my lecturers in the M.A. course in Formal Logic. He was an inspirational leader, who thought his own thoughts and was not afraid to speak his mind. I hold him in the highest regard. He was very critical of the standard Anglo-American way of doing logic, the so-called classical logic, which can be seen in everything he wrote. One of his many critical comments was: “G¨odel's(First) Theorem would not be provable using a decent logic". This contribution, written to honour him and his works, will examine this point among some others. Hilbert referred to non-constructive set theory based on classical logic as \Cantor's paradise". In this historical setting, the constructive logic and mathematics concerned was that of intuitionism. (The Preface of Mendelson [2010] refers to this.) We wish to start the process of dismantling this classi- cal paradise, and more generally classical mathematics. Our starting point will be the various diagonal-style arguments, where we examine whether the Law of Excluded Middle (LEM) is implicitly used in carrying them out. This will include the proof of G¨odel'sFirst Theorem, and also the proof of the undecidability of Turing's Halting Problem. -
The Freyd-Mitchell Embedding Theorem States the Existence of a Ring R and an Exact Full Embedding a Ñ R-Mod, R-Mod Being the Category of Left Modules Over R
The Freyd-Mitchell Embedding Theorem Arnold Tan Junhan Michaelmas 2018 Mini Projects: Homological Algebra arXiv:1901.08591v1 [math.CT] 23 Jan 2019 University of Oxford MFoCS Homological Algebra Contents 1 Abstract 1 2 Basics on abelian categories 1 3 Additives and representables 6 4 A special case of Freyd-Mitchell 10 5 Functor categories 12 6 Injective Envelopes 14 7 The Embedding Theorem 18 1 Abstract Given a small abelian category A, the Freyd-Mitchell embedding theorem states the existence of a ring R and an exact full embedding A Ñ R-Mod, R-Mod being the category of left modules over R. This theorem is useful as it allows one to prove general results about abelian categories within the context of R-modules. The goal of this report is to flesh out the proof of the embedding theorem. We shall follow closely the material and approach presented in Freyd (1964). This means we will encounter such concepts as projective generators, injective cogenerators, the Yoneda embedding, injective envelopes, Grothendieck categories, subcategories of mono objects and subcategories of absolutely pure objects. This approach is summarised as follows: • the functor category rA, Abs is abelian and has injective envelopes. • in fact, the same holds for the full subcategory LpAq of left-exact functors. • LpAqop has some nice properties: it is cocomplete and has a projective generator. • such a category embeds into R-Mod for some ring R. • in turn, A embeds into such a category. 2 Basics on abelian categories Fix some category C. Let us say that a monic A Ñ B is contained in another monic A1 Ñ B if there is a map A Ñ A1 making the diagram A B commute. -
Notes on Categorical Logic
Notes on Categorical Logic Anand Pillay & Friends Spring 2017 These notes are based on a course given by Anand Pillay in the Spring of 2017 at the University of Notre Dame. The notes were transcribed by Greg Cousins, Tim Campion, L´eoJimenez, Jinhe Ye (Vincent), Kyle Gannon, Rachael Alvir, Rose Weisshaar, Paul McEldowney, Mike Haskel, ADD YOUR NAMES HERE. 1 Contents Introduction . .3 I A Brief Survey of Contemporary Model Theory 4 I.1 Some History . .4 I.2 Model Theory Basics . .4 I.3 Morleyization and the T eq Construction . .8 II Introduction to Category Theory and Toposes 9 II.1 Categories, functors, and natural transformations . .9 II.2 Yoneda's Lemma . 14 II.3 Equivalence of categories . 17 II.4 Product, Pullbacks, Equalizers . 20 IIIMore Advanced Category Theoy and Toposes 29 III.1 Subobject classifiers . 29 III.2 Elementary topos and Heyting algebra . 31 III.3 More on limits . 33 III.4 Elementary Topos . 36 III.5 Grothendieck Topologies and Sheaves . 40 IV Categorical Logic 46 IV.1 Categorical Semantics . 46 IV.2 Geometric Theories . 48 2 Introduction The purpose of this course was to explore connections between contemporary model theory and category theory. By model theory we will mostly mean first order, finitary model theory. Categorical model theory (or, more generally, categorical logic) is a general category-theoretic approach to logic that includes infinitary, intuitionistic, and even multi-valued logics. Say More Later. 3 Chapter I A Brief Survey of Contemporary Model Theory I.1 Some History Up until to the seventies and early eighties, model theory was a very broad subject, including topics such as infinitary logics, generalized quantifiers, and probability logics (which are actually back in fashion today in the form of con- tinuous model theory), and had a very set-theoretic flavour. -
How to Adopt a Logic
How to adopt a logic Daniel Cohnitz1 & Carlo Nicolai2 1Utrecht University 2King’s College London Abstract What is commonly referred to as the Adoption Problem is a challenge to the idea that the principles for logic can be rationally revised. The argument is based on a reconstruction of unpublished work by Saul Kripke. As the reconstruction has it, Kripke essentially extends the scope of William van Orman Quine’s regress argument against conventionalism to the possibility of adopting new logical principles. In this paper we want to discuss the scope of this challenge. Are all revisions of logic subject to the regress problem? If not, are there interesting cases of logical revisions that are subject to the regress problem? We will argue that both questions should be answered negatively. FIRST DRAFT 1 1 Introduction What is commonly referred to as the Adoption Problem is a challenge to the idea that the principles for logic can be rationally revised. The argument is based on a reconstruction of unpublished work by Saul Kripke.1 As the reconstruction has it, Kripke essentially extends the scope of William van Orman Quine’s regress argument (Quine, 1976) against conventionalism to the possibility of adopting new logical principles. In this paper we want to discuss the scope of this challenge. Are all revisions of logic subject to the regress problem? If not, are there interesting cases of logical revisions that are subject to the regress problem? We will argue that both questions should be answered negatively. Kripke’s regress does not arise for all rules of inference and not even for the adoption of those rules that are of relevance for the discussion of the rational revisability of logic. -
Classifying Categories the Jordan-Hölder and Krull-Schmidt-Remak Theorems for Abelian Categories
U.U.D.M. Project Report 2018:5 Classifying Categories The Jordan-Hölder and Krull-Schmidt-Remak Theorems for Abelian Categories Daniel Ahlsén Examensarbete i matematik, 30 hp Handledare: Volodymyr Mazorchuk Examinator: Denis Gaidashev Juni 2018 Department of Mathematics Uppsala University Classifying Categories The Jordan-Holder¨ and Krull-Schmidt-Remak theorems for abelian categories Daniel Ahlsen´ Uppsala University June 2018 Abstract The Jordan-Holder¨ and Krull-Schmidt-Remak theorems classify finite groups, either as direct sums of indecomposables or by composition series. This thesis defines abelian categories and extends the aforementioned theorems to this context. 1 Contents 1 Introduction3 2 Preliminaries5 2.1 Basic Category Theory . .5 2.2 Subobjects and Quotients . .9 3 Abelian Categories 13 3.1 Additive Categories . 13 3.2 Abelian Categories . 20 4 Structure Theory of Abelian Categories 32 4.1 Exact Sequences . 32 4.2 The Subobject Lattice . 41 5 Classification Theorems 54 5.1 The Jordan-Holder¨ Theorem . 54 5.2 The Krull-Schmidt-Remak Theorem . 60 2 1 Introduction Category theory was developed by Eilenberg and Mac Lane in the 1942-1945, as a part of their research into algebraic topology. One of their aims was to give an axiomatic account of relationships between collections of mathematical structures. This led to the definition of categories, functors and natural transformations, the concepts that unify all category theory, Categories soon found use in module theory, group theory and many other disciplines. Nowadays, categories are used in most of mathematics, and has even been proposed as an alternative to axiomatic set theory as a foundation of mathematics.[Law66] Due to their general nature, little can be said of an arbitrary category. -
Diagram Chasing in Abelian Categories
Diagram Chasing in Abelian Categories Toni Annala Contents 1 Overview 2 2 Abelian Categories 3 2.1 Denition and basic properties . .3 2.2 Subobjects and quotient objects . .6 2.3 The image and inverse image functors . 11 2.4 Exact sequences and diagram chasing . 16 1 Chapter 1 Overview This is a short note, intended only for personal use, where I x diagram chasing in general abelian categories. I didn't want to take the Freyd-Mitchell embedding theorem for granted, and I didn't like the style of the Freyd's book on the topic. Therefore I had to do something else. As this was intended only for personal use, and as I decided to include this to the application quite late, I haven't touched anything in chapter 2. Some vague references to Freyd's book are made in the passing, they mean the book Abelian Categories by Peter Freyd. How diagram chasing is xed then? The main idea is to chase subobjects instead of elements. The sections 2.1 and 2.2 contain many standard statements about abelian categories, proved perhaps in a nonstandard way. In section 2.3 we dene the image and inverse image functors, which let us transfer subobjects via a morphism of objects. The most important theorem in this section is probably 2.3.11, which states that for a subobject U of X, and a morphism f : X ! Y , we have ff −1U = U \ imf. Some other results are useful as well, for example 2.3.2, which says that the image functor associated to a monic morphism is injective. -
10. Algebra Theories II 10.1 Essentially Algebraic Theory Idea: A
Page 1 of 7 10. Algebra Theories II 10.1 essentially algebraic theory Idea: A mathematical structure is essentially algebraic if its definition involves partially defined operations satisfying equational laws, where the domain of any given operation is a subset where various other operations happen to be equal. An actual algebraic theory is one where all operations are total functions. The most familiar example may be the (strict) notion of category: a small category consists of a set C0of objects, a set C1 of morphisms, source and target maps s,t:C1→C0 and so on, but composition is only defined for pairs of morphisms where the source of one happens to equal the target of the other. Essentially algebraic theories can be understood through category theory at least when they are finitary, so that all operations have only finitely many arguments. This gives a generalization of Lawvere theories, which describe finitary algebraic theories. As the domains of the operations are given by the solutions to equations, they may be understood using the notion of equalizer. So, just as a Lawvere theory is defined using a category with finite products, a finitary essentially algebraic theory is defined using a category with finite limits — or in other words, finite products and also equalizers (from which all other finite limits, including pullbacks, may be derived). Definition As alluded to above, the most concise and elegant definition is through category theory. The traditional definition is this: Definition. An essentially algebraic theory or finite limits theory is a category that is finitely complete, i.e., has all finite limits. -
Abstract Motivic Homotopy Theory
Abstract motivic homotopy theory Dissertation zur Erlangung des Grades Doktor der Naturwissenschaften (Dr. rer. nat.) des Fachbereiches Mathematik/Informatik der Universitat¨ Osnabruck¨ vorgelegt von Peter Arndt Betreuer Prof. Dr. Markus Spitzweck Osnabruck,¨ September 2016 Erstgutachter: Prof. Dr. Markus Spitzweck Zweitgutachter: Prof. David Gepner, PhD 2010 AMS Mathematics Subject Classification: 55U35, 19D99, 19E15, 55R45, 55P99, 18E30 2 Abstract Motivic Homotopy Theory Peter Arndt February 7, 2017 Contents 1 Introduction5 2 Some 1-categorical technicalities7 2.1 A criterion for a map to be constant......................7 2.2 Colimit pasting for hypercubes.........................8 2.3 A pullback calculation............................. 11 2.4 A formula for smash products......................... 14 2.5 G-modules.................................... 17 2.6 Powers in commutative monoids........................ 20 3 Abstract Motivic Homotopy Theory 24 3.1 Basic unstable objects and calculations..................... 24 3.1.1 Punctured affine spaces......................... 24 3.1.2 Projective spaces............................ 33 3.1.3 Pointed projective spaces........................ 34 3.2 Stabilization and the Snaith spectrum...................... 40 3.2.1 Stabilization.............................. 40 3.2.2 The Snaith spectrum and other stable objects............. 42 3.2.3 Cohomology theories.......................... 43 3.2.4 Oriented ring spectra.......................... 45 3.3 Cohomology operations............................. 50 3.3.1 Adams operations............................ 50 3.3.2 Cohomology operations........................ 53 3.3.3 Rational splitting d’apres` Riou..................... 56 3.4 The positive rational stable category...................... 58 3.4.1 The splitting of the sphere and the Morel spectrum.......... 58 1 1 3.4.2 PQ+ is the free commutative algebra over PQ+ ............. 59 3.4.3 Splitting of the rational Snaith spectrum................ 60 3.5 Functoriality.................................. -
Consequences of Theoretically Modeling the Mind As a Computer
PONTIFICIA UNIVERSIDAD CATOLICA DE CHILE ESCUELA DE PSICOLOGIA´ CONSEQUENCES OF THEORETICALLY MODELING THE MIND AS A COMPUTER ESTEBAN HURTADO LEON´ Thesis submitted to the Office of Research and Graduate Studies in partial fulfillment of the requirements for the degree of Doctor in Psychology Advisor: CARLOS CORNEJO ALARCON´ Santiago de Chile, August 2017 c MMXVII, ESTEBAN HURTADO PONTIFICIA UNIVERSIDAD CATOLICA DE CHILE ESCUELA DE PSICOLOGIA´ CONSEQUENCES OF THEORETICALLY MODELING THE MIND AS A COMPUTER ESTEBAN HURTADO LEON´ Members of the Committee: CARLOS CORNEJO ALARCON´ DIEGO COSMELLI SANCHEZ LUIS DISSETT VELEZ JAAN VALSINER ......... Thesis submitted to the Office of Research and Graduate Studies in partial fulfillment of the requirements for the degree of Doctor in Psychology Santiago de Chile, August 2017 c MMXVII, ESTEBAN HURTADO To Carmen and Fulvio ACKNOWLEDGEMENTS I would like to thank the School of Psychology at Pontificia Universidad Catolica´ de Chile for taking me in and walking me through the diversity of the study of the mind. I am in debt to all the teachers who kindly and passionately shared their knowledge with me, and very specially to the kind and helpful work of the administrative staff. I took my first steps in theoretical computer science at the School of Engineering of the same university, with Dr. Alvaro´ Campos, who is no longer with us. His passion for knowledge, dedication and warmth continue to inspire those of us who where lucky enough to cross paths with him. The generous and theoretically profound support of the committee members has been fundamental to the production of this text. I am deeply thankful to all of them. -
Re Ection in Conditional Rewriting Logic
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Theoretical Computer Science 285 (2002) 245–288 www.elsevier.com/locate/tcs Reection in conditional rewriting logic Manuel Clavela; ∗ JosÃe Meseguerb aFacultad de Informatica,Ã Univesidad Complutense de Madrid, Madrid, Spain bSRI International, Menlo Park, CA 94025, USA Abstract We recall general metalogical axioms for a reective logic basedon the notion of a universal theory, that is, a theory that can simulate the deductions of all other theories in a class of theories of interest, including itself. We then show that conditional rewriting logic is reective, generalizing in two stages: ÿrst to the unsortedconditionalcase, andthen to the many-sorted conditional case, the already known result for unconditional and unsorted rewriting logic (Re- ection in Rewriting Logic: Metalogical Foundations and Metaprogramming Applications. CSLI Publications, 2000). This work should be seen as providing foundations for many useful applica- tions of rewriting logic reection. The results presentedhere have greatly inuencedthe design of the Maude language, which implements rewriting logic and supports its reective capabil- ities, andhave been usedas a theoretical foundationfor applications such as internal rewrite strategies, reective design of theorem proving tools, module algebra and metaprogramming, and metareasoning in metalogical frameworks. c 2002 Elsevier Science B.V. All rights reserved. Keywords: Reection; Reective logics;