Giles’s Game and the Proof Theory of Łukasiewicz Logic

In the 1970s, Robin Giles introduced a game combining Lorenzen-style dialogue rules with a simple scheme for betting on the truth of atomic statements, and showed that the existence of winning strategies for the game corresponds to the validity of formulas in Łukasiewicz logic. In this paper, it is shown that ‘disjunctive strategies’ for Giles’s game, combining ordinary strategies for all instances of the game played on the same formula, may be interpreted as derivations in a corresponding proof system. In particular, such strategies mirror derivations in a hypersequent calculus developed in recent work on the proof theory of Łukasiewicz logic. Presented by Daniele Mundici     

An Approach to Glivenko’s Theorem in Algebraizable Logics

In a classical paper [15] V. Glivenko showed that a proposition is classically demonstrable if and only if its double negation is intuitionistically demonstrable. This result has an algebraic formulation: the double negation is a homomorphism from each Heyting algebra onto the Boolean algebra of its regular elements. Versions of both the logical and algebraic formulations of Glivenko’s theorem, adapted to other systems of logics and to algebras not necessarily related to logic can be found in the literature (see [2, 9, 8, 14] and [13, 7, 14]). The aim of this paper is to offer a general frame for studying both logical and algebraic generalizations of Glivenko’s theorem. We give abstract formulations for quasivarieties of algebras and for equivalential and algebraizable deductive systems and both formulations are compared when the quasivariety and the deductive system are related. We also analyse Glivenko’s theorem for compatible expansions of both cases. Presented by Jacek Malinowski     

Forcing in Łukasiewicz Predicate Logic

In this paper we study the notion of forcing for Łukasiewicz predicate logic (Ł∀, for short), along the lines of Robinson’s forcing in classical model theory. We deal with both finite and infinite forcing. As regard to the former we prove a Generic Model Theorem for Ł∀, while for the latter, we study the generic and existentially complete standard models of Ł∀. Presented by Jacek Malinowski     

Suszko’s Thesis,Inferential Many-valuedness,and the Notion of a Logical System

According to Suszko’s Thesis, there are but two logical values, true and false. In this paper, R. Suszko’s, G. Malinowski’s, and M. Tsuji’s analyses of logical twovaluedness are critically discussed. Another analysis is presented, which favors a notion of a logical system as encompassing possibly more than one consequence relation.

[13, p. 281]

Presented by Jacek Malinowski     

Multimo dal Logics of Products of Topologies

We introduce the horizontal and vertical topologies on the product of topological spaces, and study their relationship with the standard product topology. We show that the modal logic of products of topological spaces with horizontal and vertical topologies is the fusion S4 ⊕ S4. We axiomatize the modal logic of products of spaces with horizontal, vertical, and standard product topologies.We prove that both of these logics are complete for the product of rational numbers ℚ × ℚ with the appropriate topologies. AMS subject classification : 03B45, 54B10 The last author’s research was supported by a Social Sciences and Humanities Research Council of Canada grant number: 725-2000-2237. Presented by Melvin Fitting     

The Tense Logic for Master Argument in Prior’s Reconstruction

In this paper we examine Prior’s reconstruction of Master Argument [4] in some modal-tense logic. This logic consists of a purely tense part and Diodorean definitions of modal alethic operators. Next we study this tense logic in the pure tense language. It is the logic K _t 4 plus a new axiom (P): ‘p Λ G p ⊃ P G p’. This formula was used by Prior in his original analysis of Master Argument. (P) is usually added as an extra axiom to an axiomatization of the logic of linear time. In that case the set of moments is a total order and must be left-discrete without the least moment. However, the logic of Master Argument does not require linear time. We show what properties of the set of moments are exactly forced by (P) in the reconstruction of Prior. We make also some philosophical remarks on the analyzed reconstruction. Presented by Jacek Malinowski     

Dynamic Deontic Logic and its Paradoxes

In Meyer’s promising account [7] deontic logic is reduced to a dynamic logic. Meyer claims that with his account “we get rid of most (if not all) of the nasty paradoxes that have plagued traditional deontic logic.” But as was shown by van der Meyden in [4], Meyer’s logic also contains a paradoxical formula. In this paper we will show that another paradox can be proven, one which also effects Meyer’s “solution” to contrary to duty obligations and his logic in general. Presented by Hannes Leitgeb     

Don’t Ever Do That! Long-term Duties in <Emphasis Type="Italic">PD</Emphasis><Subscript><Emphasis Type="Italic">e</Emphasis></Subscript><Emphasis Type="Italic">L</Emphasis>

This paper studies long-term norms concerning actions. In Meyer’s Propositional Deontic Logic (PD _e L), only immediate duties can be expressed, however, often one has duties of longer durations such as: “Never do that”, or “Do this someday”. In this paper, we will investigate how to amend PD _e L so that such long-term duties can be expressed. This leads to the interesting and suprising consequence that the long-term prohibition and obligation are not interdefinable in our semantics, while there is a duality between these two notions. As a consequence, we have provided a new analysis of the long-term obligation by introducing a new atomic proposition I (indebtedness) to represent the condition that an agent has some unfulfilled obligation. Presented by Jacek Malinowski     

Symmetry as a Criterion for Comprehension Motivating Quine’s ‘New Foundations’

A common objection to Quine’s set theory “New Foundations” is that it is inadequately motivated because the restriction on comprehension which appears to avert paradox is a syntactical trick. We present a semantic criterion for determining whether a class is a set (a kind of symmetry) which motivates NF. Presented by Melvin Fitting     

Colour, world and archimedean metaphysics: stroud and the quest for reality

This paper proposes a fundamentally opposite conception of the possibility of metaphysics to that of Barry Stroud in The Quest for Reality and other writings. I discuss Stroud’s views on everyday ‚truth’ and metaphysics (Section 1), on interpretation (Section 2 – replying with a theory of ‚quasi-understanding’), and his ‚no threat’ claim (Section 3). But the main argument (Section 4) is a response to Stroud’s claim that we have no right either to affirm or to deny the metaphysical reality of colours. Stroud’s view resembles Carnap’s (1950, Revue Internationale de Philosophie 4, 20–40), that experience can in some sense never settle the metaphysical issue between e.g. materialism, idealism and phenomenalism; though we can allow everyday ‚knowledge’ e.g. that there is a fallen tree in the garden outside, as something available on all three views. (Carnap takes the undecidability as a sign that the metaphysical issue is a pseudo-question; Stroud insists it is factual, but places it beyond our ken, ‚external’.) I argue, instead, that metaphysical argument is possible from within our conceptual scheme and epistemic situation (as in Gareth Evans’s arguments for realism over phenomenalism); that ‚external’ and ‚internal’ questions cannot be separated as Stroud wishes; and that if we really were denied knowledge on ‚metaphysical’ matters, that would infect our right to claim knowledge of ‚observational’ matters too. And I sketch a theory of colour that would allow us to conclude (at once ‚metaphysically’ and ‚internally’) that things are indeed ‚really’ coloured. For all his expressions of sympathy for Wittgenstein, Stroud’s metaphysics is remarkably Cartesian.     

On Reduction Rules,Meaning-as-use,and Proof-theoretic Semantics

The intention here is that of giving a formal underpinning to the idea of ‘meaning-is-use’ which, even if based on proofs, it is rather different from proof-theoretic semantics as in the Dummett–Prawitz tradition. Instead, it is based on the idea that the meaning of logical constants are given by the explanation of immediate consequences, which in formalistic terms means the effect of elimination rules on the result of introduction rules, i.e. the so-called reduction rules. For that we suggest an extension to the Curry– Howard interpretation which draws on the idea of labelled deduction, and brings back Frege’s device of variable-abstraction to operate on the labels (i.e., proof-terms) alongside formulas of predicate logic. Presented by Heinrich Wansing     

Yet Another Run around the Circle

In a recent article, D. A. Truncellito (2004, ‘Running in Circles about Begging the Question’, Argumentation 18, 325–329) argues that the discussion between Robinson (1971, ‘Begging the Question’, Analysis 31, 113–117), Sorensen (1996, ‘Unbeggable Questions’, Analysis 56, 51–55) and Teng (1997, ‘Sorensen on Begging the Question’, Analysis 57, 220–222) shows that we need to distinguish between logical fallacies, which are mistakes in the form of the argument, and rhetorical fallacies, which are mistakes committed by the arguer. While I basically agree with Truncellito’s line of thinking, I believe this distinction is not tenable and offer a different view. In addition, I will argue that the conclusion to draw from the abovementioned discussion is that validity is not a sufficient criterion of begging the question, and that we should be wary of the containment-metaphor of a deductive argument.     

Jump Liars and Jourdain’s Card via the Relativized T-scheme

A relativized version of Tarski’s T-scheme is introduced as a new principle of the truth predicate. Under the relativized T-scheme, the paradoxical objects, such as the Liar sentence and Jourdain’s card sequence, are found to have certain relative contradictoriness. That is, they are contradictory only in some frames in the sense that any valuation admissible for them in these frames will lead to a contradiction. It is proved that for any positive integer n, the n-jump liar sentence is contradictory in and only in those frames containing at least an n-jump odd cycle. In particular, the Liar sentence is contradictory in and only in those frames containing at least an odd cycle. The Liar sentence is also proved to be less contradictory than Jourdain’s card sequence: the latter must be contradictory in those frames where the former is so, but not vice versa. Generally, the relative contradictoriness is the common characteristic of the paradoxical objects, but different paradoxical objects may have different relative contradictoriness. Presented by Heinrich Wansing     

Against Against Intuitionism

The main ideas behind Brouwer’s philosophy of Intuitionism are presented. Then some critical remarks against Intuitionism made by William Tait in “Against Intuitionism” [Journal of Philosophical Logic, 12, 173–195] are answered.     

Warrant without truth?

This paper advances the debate over the question whether false beliefs may nevertheless have warrant, the property that yields knowledge when conjoined with true belief. The paper’s first main part—which spans Sections 2–4—assesses the best argument for Warrant Infallibilism, the view that only true beliefs can have warrant. I show that this argument’s key premise conflicts with an extremely plausible claim about warrant. Sections 5–6 constitute the paper’s second main part. Section 5 presents an overlooked puzzle about warrant, and uses that puzzle to generate a new argument for Warrant Fallibilism, the view that false beliefs can have warrant. Section 6 evaluates this pro-Fallibilism argument, finding ultimately that it defeats itself in a surprising way. I conclude that neither Infallibilism nor Fallibilism should now constrain theorizing about warrant.     

A Few More Useful 8-valued Logics for Reasoning with Tetralattice <Emphasis Type="Italic">EIGHT</Emphasis><Subscript>4</Subscript>

In their useful logic for a computer network Shramko and Wansing generalize initial values of Belnap’s 4-valued logic to the set 16 to be the power-set of Belnap’s 4. This generalization results in a very specific algebraic structure — the trilattice SIXTEEN ₃ with three orderings: information, truth and falsity. In this paper, a slightly different way of generalization is presented. As a base for further generalization a set 3 is chosen, where initial values are a — incoming data is asserted, d — incoming data is denied, and u — incoming data is neither asserted nor denied, that corresponds to the answer “don’t know”. In so doing, the power-set of 3, that is the set 8 is considered. It turns out that there are not three but four orderings naturally defined on the set 8 that form the tetralattice EIGHT ₄. Besides three ordering relations mentioned above it is an extra uncertainty ordering. Quite predictably, the logics generated by a–order (truth order) and d–order (falsity order) coincide with first-degree entailment. Finally logic with two kinds of operations (a–connectives and d–connectives) and consequence relation defined via a–ordering is considered. An adequate axiomatization for this logic is proposed.     

Group problem-solving among teachers: A case study of how to improve a colleague’s teaching

A case study of six teachers cooperating to improve a teacher’s teaching showed the dynamics of the group problem-solving process. An analysis of their verbal interactions showed the importance of shared understanding to successful group problem solving. The cooperative group structure helped members resolve cognitive conflicts and build group understanding. During this process, the members’ past teaching experiences and knowledge contributed to their conceptualization of the teacher’s teaching problems and their proposed solutions to improve the teacher’s teaching. Tsz Cheung Lam graduated from the Department of Educational Psychology at the Chinese University of Hong Kong in 2004 and obtained his Master of Education degree. His research interests lie primarily on cooperative learning and problem solving. As a primary school teacher in practice, he is now studying part-time for another master degree in data science at the Department of Statistics of the Chinese University of Hong Kong.     

Lakatos’s Challenge? Auxiliary Hypotheses and Non-Monotonous Inference

Summary  Gerhard Schurz [2001, Journal for General Philosophy of Science, 32, 65–107] has proposed to reconstruct auxiliary hypothesis addition, e.g., postulation of Neptune to immunize Newtonian mechanics, with concepts from non-monotonous inference to avoid the retention of false predictions that are among the consequence-set of the deductive model. However, the non-monotonous reconstruction retains the observational premise that is indeed rejected in the deductive model. Hence, his proposal fails to do justice to Lakatos’ core-belt model, therefore fails to meet what Schurz coined “Lakatos’ challenge”. It is argued that Lakatos’s distinction between core and belt of a research program is not mapable onto premise-set and consequence-set and that Schurz’s understanding of a ceteris paribus clause as a transfinite list of (absent) interfering factors is problematic. I propose a simple reading of Lakatos’s use of the term ceteris paribus clause and motivate why the term hypothesis addition, despite not being interpretable literally, came to be entrenched.

It is not that we propose a theory and Nature may shout NO; rather we propose a maze of theories and Nature may shout INCONSISTENT. Lakatos (1978, p. 45)

     

An Institution-Independent Proof of the Robinson Consistency Theorem

We prove an institutional version of A. Robinson’s Consistency Theorem. This result is then appliedto the institution of many-sorted first-order predicate logic and to two of its variations, infinitary and partial, obtaining very general syntactic criteria sufficient for a signature square in order to satisfy the Robinson consistency and Craig interpolation properties. Presented by Robert Goldblatt