Negation and Opposition

2020 ◽  
pp. 6-25
Author(s):  
Laurence R. Horn
Keyword(s):  
Semantic Category ◽  
Syntactic Category ◽  
Square Of Opposition ◽  
Double Negation ◽  
Law Of Excluded Middle ◽  
Truth Value ◽  
The Law ◽  
Excluded Middle

The treatment of negation has long been linked to the treatment of opposition between propositions (or sentences) and between terms (or subsentential constituents). The primary types of opposition, usefully displayed on the post-Aristotelian Square of Opposition, are contradiction (two contradictories always differ in truth value) and contrariety (two contraries can both be false, but not both be true). The law of non-contradiction governs both oppositions, while the law of excluded middle applies only to contradictories. In principle, Aristotle’s semantic category of contradictory opposition lines up with the syntactic category of sentence (vs. constituent) negation, but in practice matters are more complicated, and while Klima’s diagnostics are helpful they are often not decisive. These complications are illustrated by the distribution of affixal negation, the phenomenon of logical double negation, the interaction of negation with quantifiers and modals, and the tendency for formal contradictory negation to be pragmatically strengthened to contrariety.

Revenge, I

2018 ◽  
Author(s):  
Keith Simmons
Keyword(s):  
Natural Language ◽  
Liar Paradox ◽  
Critical Discussion ◽  
Kripke’S Theory Of Truth ◽  
Law Of Excluded Middle ◽  
Truth Value ◽  
The Law ◽  
The Liar ◽  
The Liar Paradox ◽  
Excluded Middle

Chapter 8 is the first of two chapters on the phenomenon of revenge paradoxes, paradoxes which, roughly speaking, are constructed out of the very terms of a purported solution. The chapter begins by exploring the difficulties that revenge presents for Kripke’s theory of truth, in either of two versions: a version that admits truth value gaps, and a paracomplete version which rejects the law of excluded middle. The chapter goes on to critically examine Field’s paracomplete theory of truth and its treatment of revenge, arguing that Field’s theory is couched in terms that are artificial and too far removed from natural language. The chapter concludes with a critical discussion of Priest’s dialetheist approach to the Liar paradox, according to which there are true contradictions. It is argued that Priest’s theory is itself subject to revenge paradoxes.

Reconsidering Kant’s Rejection of Indirect Arguments in Transcendental Philosophy

2021 ◽  
pp. 1-19
Author(s):  
Marcel Buß
Keyword(s):  
Immanuel Kant ◽  
Explanatory Power ◽  
Transcendental Philosophy ◽  
Point Of View ◽  
Transcendental Arguments ◽  
Mathematical Proofs ◽  
Law Of Excluded Middle ◽  
The Law ◽  
Excluded Middle ◽  
Insight Into

Abstract Immanuel Kant states that indirect arguments are not suitable for the purposes of transcendental philosophy. If he is correct, this affects contemporary versions of transcendental arguments which are often used as an indirect refutation of scepticism. I discuss two reasons for Kant’s rejection of indirect arguments. Firstly, Kant argues that we are prone to misapply the law of excluded middle in philosophical contexts. Secondly, Kant points out that indirect arguments lack some explanatory power. They can show that something is true but they do not provide insight into why something is true. Using mathematical proofs as examples, I show that this is because indirect arguments are non-constructive. From a Kantian point of view, transcendental arguments need to be constructive in some way. In the last part of the paper, I briefly examine a comment made by P. F. Strawson. In my view, this comment also points toward a connection between transcendental and constructive reasoning.

On Weakening the Law of Excluded Middle

Dialogue ◽  
1966 ◽  
Vol 5 (2) ◽  
pp. 232-236
Author(s):  
Douglas Odegard
Keyword(s):  
Law Of Excluded Middle ◽  
The Law ◽  
Excluded Middle

Let us use ‘false’ and ‘not true’ (and cognates) in such a way that the latter expression covers the broader territory of the two; in other words, a statement's falsity implies its non-truth but not vice versa. For example, ‘John is ill’ cannot be false without being nontrue; but it can be non-true without being false, since it may not be true when ‘John is not ill’ is also not true, a situation we could describe by saying ‘It is neither the case that John is ill nor the case that John is not ill.’

The Law of Excluded Middle

Mind ◽  
1978 ◽  
Vol LXXXVII (2) ◽  
pp. 161-180 ◽  
Author(s):  
NEIL COOPER
Keyword(s):  
Law Of Excluded Middle ◽  
The Law ◽  
Excluded Middle

Frege's theorem in a constructive setting

1999 ◽  
Vol 64 (2) ◽  
pp. 486-488 ◽  
Author(s):  
John L. Bell
Keyword(s):  
Set Theory ◽  
Natural Numbers ◽  
The Family ◽  
Power Set ◽  
Law Of Excluded Middle ◽  
The Law ◽  
Image Position ◽  
Excluded Middle ◽  
Intuitionistic Set Theory

By Frege's Theorem is meant the result, implicit in Frege's Grundlagen, that, for any set E, if there exists a map υ from the power set of E to E satisfying the conditionthen E has a subset which is the domain of a model of Peano's axioms for the natural numbers. (This result is proved explicitly, using classical reasoning, in Section 3 of [1].) My purpose in this note is to strengthen this result in two directions: first, the premise will be weakened so as to require only that the map υ be defined on the family of (Kuratowski) finite subsets of the set E, and secondly, the argument will be constructive, i.e., will involve no use of the law of excluded middle. To be precise, we will prove, in constructive (or intuitionistic) set theory, the followingTheorem. Let υ be a map with domain a family of subsets of a set E to E satisfying the following conditions:(i) ø ϵdom(υ)(ii)∀U ϵdom(υ)∀x ϵ E − UU ∪ x ϵdom(υ)(iii)∀UV ϵdom(5) υ(U) = υ(V) ⇔ U ≈ V.Then we can define a subset N of E which is the domain of a model of Peano's axioms.

scholarly journals Validating Brouwer's continuity principle for numbers using named exceptions

2017 ◽  
Vol 28 (6) ◽  
pp. 942-990 ◽  
Author(s):  
VINCENT RAHLI ◽  
MARK BICKFORD
Keyword(s):  
Equivalence Relation ◽  
Dependent Types ◽  
Proof Assistant ◽  
Continuity Theorem ◽  
Continuity Principle ◽  
Fan Theorem ◽  
Law Of Excluded Middle ◽  
The Law ◽  
Intuitionistic Mathematics ◽  
Excluded Middle

This paper extends the Nuprl proof assistant (a system representative of the class of extensional type theories with dependent types) withnamed exceptionsandhandlers, as well as a nominalfreshoperator. Using these new features, we prove a version of Brouwer's continuity principle for numbers. We also provide a simpler proof of a weaker version of this principle that only uses diverging terms. We prove these two principles in Nuprl's metatheory using our formalization of Nuprl in Coq and reflect these metatheoretical results in the Nuprl theory as derivation rules. We also show that these additions preserve Nuprl's key metatheoretical properties, in particular consistency and the congruence of Howe's computational equivalence relation. Using continuity and the fan theorem, we prove important results of Intuitionistic Mathematics: Brouwer's continuity theorem, bar induction on monotone bars and the negation of the law of excluded middle.

A proof–technique in uniform space theory

2003 ◽  
Vol 68 (3) ◽  
pp. 795-802 ◽  
Author(s):  
Douglas Bridges ◽  
Luminiţa Vîţă
Keyword(s):  
Uniform Space ◽  
Weak Form ◽  
Space Theory ◽  
Proof Technique ◽  
Uniform Spaces ◽  
Constructive Theory ◽  
Law Of Excluded Middle ◽  
The Law ◽  
Excluded Middle

AbstractIn the constructive theory of uniform spaces there occurs a technique of proof in which the application of a weak form of the law of excluded middle is circumvented by purely analytic means. The essence of this proof–technique is extracted and then applied in several different situations.

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