On the Semantics of Classical First-Order Logic with Constructive Double Negation
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Semantical Investigations
Bulletin of the Section of Logic Volume 49/3 (2020), pp. 231{253 http://dx.doi.org/10.18778/0138-0680.2020.12 Satoru Niki EMPIRICAL NEGATION, CO-NEGATION AND THE CONTRAPOSITION RULE I: SEMANTICAL INVESTIGATIONS Abstract We investigate the relationship between M. De's empirical negation in Kripke and Beth Semantics. It turns out empirical negation, as well as co-negation, corresponds to different logics under different semantics. We then establish the relationship between logics related to these negations under unified syntax and semantics based on R. Sylvan's CC!. Keywords: Empirical negation, co-negation, Beth semantics, Kripke semantics, intuitionism. 1. Introduction The philosophy of Intuitionism has long acknowledged that there is more to negation than the customary, reduction to absurdity. Brouwer [1] has al- ready introduced the notion of apartness as a positive version of inequality, such that from two apart objects (e.g. points, sequences) one can learn not only they are unequal, but also how much or where they are different. (cf. [19, pp.319{320]). He also introduced the notion of weak counterexample, in which a statement is reduced to a constructively unacceptable principle, to conclude we cannot expect to prove the statement [17]. Presented by: Andrzej Indrzejczak Received: April 18, 2020 Published online: August 15, 2020 c Copyright for this edition by UniwersytetL´odzki, L´od´z2020 232 Satoru Niki Another type of negation was discussed in the dialogue of Heyting [8, pp. 17{19]. In it mathematical negation characterised by reduction to absurdity is distinguished from factual negation, which concerns the present state of our knowledge. -
7.1 Rules of Implication I
Natural Deduction is a method for deriving the conclusion of valid arguments expressed in the symbolism of propositional logic. The method consists of using sets of Rules of Inference (valid argument forms) to derive either a conclusion or a series of intermediate conclusions that link the premises of an argument with the stated conclusion. The First Four Rules of Inference: ◦ Modus Ponens (MP): p q p q ◦ Modus Tollens (MT): p q ~q ~p ◦ Pure Hypothetical Syllogism (HS): p q q r p r ◦ Disjunctive Syllogism (DS): p v q ~p q Common strategies for constructing a proof involving the first four rules: ◦ Always begin by attempting to find the conclusion in the premises. If the conclusion is not present in its entirely in the premises, look at the main operator of the conclusion. This will provide a clue as to how the conclusion should be derived. ◦ If the conclusion contains a letter that appears in the consequent of a conditional statement in the premises, consider obtaining that letter via modus ponens. ◦ If the conclusion contains a negated letter and that letter appears in the antecedent of a conditional statement in the premises, consider obtaining the negated letter via modus tollens. ◦ If the conclusion is a conditional statement, consider obtaining it via pure hypothetical syllogism. ◦ If the conclusion contains a letter that appears in a disjunctive statement in the premises, consider obtaining that letter via disjunctive syllogism. Four Additional Rules of Inference: ◦ Constructive Dilemma (CD): (p q) • (r s) p v r q v s ◦ Simplification (Simp): p • q p ◦ Conjunction (Conj): p q p • q ◦ Addition (Add): p p v q Common Misapplications Common strategies involving the additional rules of inference: ◦ If the conclusion contains a letter that appears in a conjunctive statement in the premises, consider obtaining that letter via simplification. -
Two Sources of Explosion
Two sources of explosion Eric Kao Computer Science Department Stanford University Stanford, CA 94305 United States of America Abstract. In pursuit of enhancing the deductive power of Direct Logic while avoiding explosiveness, Hewitt has proposed including the law of excluded middle and proof by self-refutation. In this paper, I show that the inclusion of either one of these inference patterns causes paracon- sistent logics such as Hewitt's Direct Logic and Besnard and Hunter's quasi-classical logic to become explosive. 1 Introduction A central goal of a paraconsistent logic is to avoid explosiveness { the inference of any arbitrary sentence β from an inconsistent premise set fp; :pg (ex falso quodlibet). Hewitt [2] Direct Logic and Besnard and Hunter's quasi-classical logic (QC) [1, 5, 4] both seek to preserve the deductive power of classical logic \as much as pos- sible" while still avoiding explosiveness. Their work fits into the ongoing research program of identifying some \reasonable" and \maximal" subsets of classically valid rules and axioms that do not lead to explosiveness. To this end, it is natural to consider which classically sound deductive rules and axioms one can introduce into a paraconsistent logic without causing explo- siveness. Hewitt [3] proposed including the law of excluded middle and the proof by self-refutation rule (a very special case of proof by contradiction) but did not show whether the resulting logic would be explosive. In this paper, I show that for quasi-classical logic and its variant, the addition of either the law of excluded middle or the proof by self-refutation rule in fact leads to explosiveness. -
Introduction Nml:Syn:Int: Modal Logic Deals with Modal Propositions and the Entailment Relations Among Sec Them
syn.1 Introduction nml:syn:int: Modal logic deals with modal propositions and the entailment relations among sec them. Examples of modal propositions are the following: 1. It is necessary that 2 + 2 = 4. 2. It is necessarily possible that it will rain tomorrow. 3. If it is necessarily possible that ' then it is possible that '. Possibility and necessity are not the only modalities: other unary connectives are also classified as modalities, for instance, \it ought to be the case that '," \It will be the case that '," \Dana knows that '," or \Dana believes that '." Modal logic makes its first appearance in Aristotle's De Interpretatione: he was the first to notice that necessity implies possibility, but not vice versa; that possibility and necessity are inter-definable; that If ' ^ is possibly true then ' is possibly true and is possibly true, but not conversely; and that if ' ! is necessary, then if ' is necessary, so is . The first modern approach to modal logic was the work of C. I. Lewis,cul- minating with Lewis and Langford, Symbolic Logic (1932). Lewis & Langford were unhappy with the representation of implication by means of the mate- rial conditional: ' ! is a poor substitute for \' implies ." Instead, they proposed to characterize implication as \Necessarily, if ' then ," symbolized as ' J . In trying to sort out the different properties, Lewis identified five different modal systems, S1,..., S4, S5, the last two of which are still in use. The approach of Lewis and Langford was purely syntactical: they identified reasonable axioms and rules and investigated what was provable with those means. -
On the Logic of Two-Dimensional Semantics
Matrices and Modalities: On the Logic of Two-Dimensional Semantics MSc Thesis (Afstudeerscriptie) written by Peter Fritz (born March 4, 1984 in Ludwigsburg, Germany) under the supervision of Dr Paul Dekker and Prof Dr Yde Venema, and submitted to the Board of Examiners in partial fulfillment of the requirements for the degree of MSc in Logic at the Universiteit van Amsterdam. Date of the public defense: Members of the Thesis Committee: June 29, 2011 Dr Paul Dekker Dr Emar Maier Dr Alessandra Palmigiano Prof Dr Frank Veltman Prof Dr Yde Venema Abstract Two-dimensional semantics is a theory in the philosophy of language that pro- vides an account of meaning which is sensitive to the distinction between ne- cessity and apriority. Usually, this theory is presented in an informal manner. In this thesis, I take first steps in formalizing it, and use the formalization to present some considerations in favor of two-dimensional semantics. To do so, I define a semantics for a propositional modal logic with operators for the modalities of necessity, actuality, and apriority that captures the relevant ideas of two-dimensional semantics. I use this to show that some criticisms of two- dimensional semantics that claim that the theory is incoherent are not justified. I also axiomatize the logic, and compare it to the most important proposals in the literature that define similar logics. To indicate that two-dimensional semantics is a plausible semantic theory, I give an argument that shows that all theorems of the logic can be philosophically justified independently of two-dimensional semantics. Acknowledgements I thank my supervisors Paul Dekker and Yde Venema for their help and encour- agement in preparing this thesis. -
Contradiction Or Non-Contradiction? Hegel’S Dialectic Between Brandom and Priest
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Padua@research CONTRADICTION OR NON-CONTRADICTION? HEGEL’S DIALECTIC BETWEEN BRANDOM AND PRIEST by Michela Bordignon Abstract. The aim of the paper is to analyse Brandom’s account of Hegel’s conception of determinate negation and the role this structure plays in the dialectical process with respect to the problem of contradiction. After having shown both the merits and the limits of Brandom’s account, I will refer to Priest’s dialetheistic approach to contradiction as an alternative contemporary perspective from which it is possible to capture essential features of Hegel’s notion of contradiction, and I will test the equation of Hegel’s dialectic with Priest dialetheism. 1. Introduction According to Horstmann, «Hegel thinks of his new logic as being in part incompatible with traditional logic»1. The strongest expression of this new conception of logic is the first thesis of the work Hegel wrote in 1801 in order to earn his teaching habilitation: «contradictio est regula veri, non contradictio falsi»2. Hegel seems to claim that contradictions are true. The Hegelian thesis of the truth of contradiction is highly problematic. This is shown by Popper’s critique based on the principle of ex falso quodlibet: «if a theory contains a contradiction, then it entails everything, and therefore, indeed, nothing […]. A theory which involves a contradiction is therefore entirely useless I thank Graham Wetherall for kindly correcting a previous English translation of this paper and for his suggestions and helpful remarks. Of course, all remaining errors are mine. -
Notes on Proof Theory
Notes on Proof Theory Master 1 “Informatique”, Univ. Paris 13 Master 2 “Logique Mathématique et Fondements de l’Informatique”, Univ. Paris 7 Damiano Mazza November 2016 1Last edit: March 29, 2021 Contents 1 Propositional Classical Logic 5 1.1 Formulas and truth semantics . 5 1.2 Atomic negation . 8 2 Sequent Calculus 10 2.1 Two-sided formulation . 10 2.2 One-sided formulation . 13 3 First-order Quantification 16 3.1 Formulas and truth semantics . 16 3.2 Sequent calculus . 19 3.3 Ultrafilters . 21 4 Completeness 24 4.1 Exhaustive search . 25 4.2 The completeness proof . 30 5 Undecidability and Incompleteness 33 5.1 Informal computability . 33 5.2 Incompleteness: a road map . 35 5.3 Logical theories . 38 5.4 Arithmetical theories . 40 5.5 The incompleteness theorems . 44 6 Cut Elimination 47 7 Intuitionistic Logic 53 7.1 Sequent calculus . 55 7.2 The relationship between intuitionistic and classical logic . 60 7.3 Minimal logic . 65 8 Natural Deduction 67 8.1 Sequent presentation . 68 8.2 Natural deduction and sequent calculus . 70 8.3 Proof tree presentation . 73 8.3.1 Minimal natural deduction . 73 8.3.2 Intuitionistic natural deduction . 75 1 8.3.3 Classical natural deduction . 75 8.4 Normalization (cut-elimination in natural deduction) . 76 9 The Curry-Howard Correspondence 80 9.1 The simply typed l-calculus . 80 9.2 Product and sum types . 81 10 System F 83 10.1 Intuitionistic second-order propositional logic . 83 10.2 Polymorphic types . 84 10.3 Programming in system F ...................... 85 10.3.1 Free structures . -
Chapter 1 Negation in a Cross-Linguistic Perspective
Chapter 1 Negation in a cross-linguistic perspective 0. Chapter summary This chapter introduces the empirical scope of our study on the expression and interpretation of negation in natural language. We start with some background notions on negation in logic and language, and continue with a discussion of more linguistic issues concerning negation at the syntax-semantics interface. We zoom in on cross- linguistic variation, both in a synchronic perspective (typology) and in a diachronic perspective (language change). Besides expressions of propositional negation, this book analyzes the form and interpretation of indefinites in the scope of negation. This raises the issue of negative polarity and its relation to negative concord. We present the main facts, criteria, and proposals developed in the literature on this topic. The chapter closes with an overview of the book. We use Optimality Theory to account for the syntax and semantics of negation in a cross-linguistic perspective. This theoretical framework is introduced in Chapter 2. 1 Negation in logic and language The main aim of this book is to provide an account of the patterns of negation we find in natural language. The expression and interpretation of negation in natural language has long fascinated philosophers, logicians, and linguists. Horn’s (1989) Natural history of negation opens with the following statement: “All human systems of communication contain a representation of negation. No animal communication system includes negative utterances, and consequently, none possesses a means for assigning truth value, for lying, for irony, or for coping with false or contradictory statements.” A bit further on the first page, Horn states: “Despite the simplicity of the one-place connective of propositional logic ( ¬p is true if and only if p is not true) and of the laws of inference in which it participate (e.g. -
A Non-Classical Refinement of the Interpolation Property for Classical
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Stirling Online Research Repository – Accepted for publication in Logique & Analyse – A non-classical refinement of the interpolation property for classical propositional logic Peter Milne Abstract We refine the interpolation property of the f^; _; :g-fragment of classical propositional logic, showing that if 2 :φ, 2 and φ then there is an interpolant χ, constructed using at most atomic formulas occurring in both φ and and negation, conjunction and disjunction, such that (i) φ entails χ in Kleene’s strong three-valued logic and (ii) χ entails in Priest’s Logic of Paradox. Keywords: Interpolation theorem for classical propositional logic · Kleene’s strong 3-valued logic · Priest’s Logic of Paradox 1 Introduction Suppose that φ classically entails , that φ is not a classical contradiction and that is not a classical tautology. Then φ and must share non-logical vo- cabulary, for else one could make φ true and false at the same time. That there must be some overlap in non-logical vocabulary between premise and con- clusion is obvious. Possession of the interpolation property takes this line of thought much further: If 2 :φ, 2 and φ then there is a formula χ containing only atomic formulas common to φ and and such that φ χ and χ .1 1Surprisingly few textbooks prove this theorem. (Hodges 2001) and (Hunter 1971) are excep- tions. They prove it in the slightly stronger form if φ and at least one atomic formula is common to φ and then there is a formula χ containing only atomic formulas common to φ and and such that φ χ and χ . -
Probabilistic Semantics for Modal Logic
Probabilistic Semantics for Modal Logic By Tamar Ariela Lando A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Philosophy in the Graduate Division of the University of California, Berkeley Committee in Charge: Paolo Mancosu (Co-Chair) Barry Stroud (Co-Chair) Christos Papadimitriou Spring, 2012 Abstract Probabilistic Semantics for Modal Logic by Tamar Ariela Lando Doctor of Philosophy in Philosophy University of California, Berkeley Professor Paolo Mancosu & Professor Barry Stroud, Co-Chairs We develop a probabilistic semantics for modal logic, which was introduced in recent years by Dana Scott. This semantics is intimately related to an older, topological semantics for modal logic developed by Tarski in the 1940’s. Instead of interpreting modal languages in topological spaces, as Tarski did, we interpret them in the Lebesgue measure algebra, or algebra of measurable subsets of the real interval, [0, 1], modulo sets of measure zero. In the probabilistic semantics, each formula is assigned to some element of the algebra, and acquires a corresponding probability (or measure) value. A formula is satisfed in a model over the algebra if it is assigned to the top element in the algebra—or, equivalently, has probability 1. The dissertation focuses on questions of completeness. We show that the propo- sitional modal logic, S4, is sound and complete for the probabilistic semantics (formally, S4 is sound and complete for the Lebesgue measure algebra). We then show that we can extend this semantics to more complex, multi-modal languages. In particular, we prove that the dynamic topological logic, S4C, is sound and com- plete for the probabilistic semantics (formally, S4C is sound and complete for the Lebesgue measure algebra with O-operators). -
Chapter 10: Symbolic Trails and Formal Proofs of Validity, Part 2
Essential Logic Ronald C. Pine CHAPTER 10: SYMBOLIC TRAILS AND FORMAL PROOFS OF VALIDITY, PART 2 Introduction In the previous chapter there were many frustrating signs that something was wrong with our formal proof method that relied on only nine elementary rules of validity. Very simple, intuitive valid arguments could not be shown to be valid. For instance, the following intuitively valid arguments cannot be shown to be valid using only the nine rules. Somalia and Iran are both foreign policy risks. Therefore, Iran is a foreign policy risk. S I / I Either Obama or McCain was President of the United States in 2009.1 McCain was not President in 2010. So, Obama was President of the United States in 2010. (O v C) ~(O C) ~C / O If the computer networking system works, then Johnson and Kaneshiro will both be connected to the home office. Therefore, if the networking system works, Johnson will be connected to the home office. N (J K) / N J Either the Start II treaty is ratified or this landmark treaty will not be worth the paper it is written on. Therefore, if the Start II treaty is not ratified, this landmark treaty will not be worth the paper it is written on. R v ~W / ~R ~W 1 This or statement is obviously exclusive, so note the translation. 427 If the light is on, then the light switch must be on. So, if the light switch in not on, then the light is not on. L S / ~S ~L Thus, the nine elementary rules of validity covered in the previous chapter must be only part of a complete system for constructing formal proofs of validity. -
Kripke Semantics for Basic Sequent Systems
Kripke Semantics for Basic Sequent Systems Arnon Avron and Ori Lahav? School of Computer Science, Tel Aviv University, Israel {aa,orilahav}@post.tau.ac.il Abstract. We present a general method for providing Kripke seman- tics for the family of fully-structural multiple-conclusion propositional sequent systems. In particular, many well-known Kripke semantics for a variety of logics are easily obtained as special cases. This semantics is then used to obtain semantic characterizations of analytic sequent sys- tems of this type, as well as of those admitting cut-admissibility. These characterizations serve as a uniform basis for semantic proofs of analyt- icity and cut-admissibility in such systems. 1 Introduction This paper is a continuation of an on-going project aiming to get a unified semantic theory and understanding of analytic Gentzen-type systems and the phenomenon of strong cut-admissibility in them. In particular: we seek for gen- eral effective criteria that can tell in advance whether a given system is analytic, and whether the cut rule is (strongly) admissible in it (instead of proving these properties from scratch for every new system). The key idea of this project is to use semantic tools which are constructed in a modular way. For this it is es- sential to use non-deterministic semantics. This was first done in [6], where the family of propositional multiple-conclusion canonical systems was defined, and it was shown that the semantics of such systems is provided by two-valued non- deterministic matrices { a natural generalization of the classical truth-tables. The sequent systems of this family are fully-structural (i.e.