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7Epistemic entrenchment with incomparabilities and relational belief revisionIn André Fuhrmann & Michael Morreau (eds.), The Logic of Theory Change: Workshop, Konstanz, FRG, October 13-15, 1989, Proceedings, Springer. pp. 93--126. 1991.
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23A semantic approach to nonmonotonic reasoning: Inference operations and choiceTheoria 88 (3): 494-528. 2022.Theoria, Volume 88, Issue 3, Page 494-528, June 2022.
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Artificiell Intelligens: Tankar utan innehåll?In Åke E. Andersson & Nils-Eric Sahlin (eds.), Huvudinnehåll: tolv filosofiska uppsatser, . pp. 121-146. 1993.Artificiell intelligens (AI) är ett ungt forskningsområde där många av de grundläggande problemen förefaller att vara av filosofisk art.1 Ämnet har sina filosofiska rötter dels i traditionen från Leibniz, Frege, Russell och Hilbert, som strävar efter att formalisera principerna för exakt tänkande, dels i den klassiska mekanismen: idén att människan är en maskin och att det mänskliga tänkandet är en mekanisk process. Som en första approximation kan vi säga att AI är det vetenskapliga studiet av h…Read more
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214Paradoxes of DemonstrabilityIn Lars-Göran Johansson, Jan Österberg & Rysiek Śliwiński (eds.), Logic, Ethics and All That Jazz: Essays in Honour of Jordan Howard Sobel, Dept. of Philosophy, Uppsala University. pp. 177-185. 2009.In this paper I consider two paradoxes that arise in connection with the concept of demonstrability, or absolute provability. I assume—for the sake of the argument—that there is an intuitive notion of demonstrability, which should not be conflated with the concept of formal deducibility in a (formal) system or the relativized concept of provability from certain axioms. Demonstrability is an epistemic concept: the rough idea is that a sentence is demonstrable if it is provable from knowable basic…Read more
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Physicalism, Consciousness, and Modality: Essays in the Philosophy of Mind (edited book)Department of Philosophy and Linguistics, Umeå University. 2002.
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282Thinking Impossible ThingsIn Sten Lindström & Pär Sundström (eds.), Physicalism, Consciousness, and Modality: Essays in the Philosophy of Mind, Department of Philosophy and Linguistics, Umeå University. pp. 125-132. 2002.“There is no use in trying,” said Alice; “one can’t believe impossible things.” “I dare say you haven’t had much practice,” said the Queen. “When I was your age, I always did it for half an hour a day. Why, sometimes I’ve believed as many as six impossible things before breakfast”. Lewis Carroll, Through the Looking Glass. It is a rather common view among philosophers that one cannot, properly speaking, be said to believe, conceive, imagine, hope for, or seek what is impossible. Some philosopher…Read more
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222This paper presents a uniform semantic treatment of nonmonotonic inference operations that allow for inferences from infinite sets of premises. The semantics is formulated in terms of selection functions and is a generalization of the preferential semantics of Shoham (1987), (1988), Kraus, Lehman, and Magidor (1990) and Makinson (1989), (1993). A selection function picks out from a given set of possible states (worlds, situations, models) a subset consisting of those states that are, in some sen…Read more
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389Extending Dynamic Doxastic Logic: Accommodating Iterated Beliefs And Ramsey Conditionals Within DDLIn Jan Odelstad, Lars Lindahl, Paul Needham & Rysiek Sliwi Nski (eds.), For Good Measure, . 1997.In this paper we distinguish between various kinds of doxastic theories. One distinction is between informal and formal doxastic theories. AGM-type theories of belief change are of the former kind, while Hintikka’s logic of knowledge and belief is of the latter. Then we distinguish between static theories that study the unchanging beliefs of a certain agent and dynamic theories that investigate not only the constraints that can reasonably be imposed on the doxastic states of a rational agent but…Read more
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233Church-Fitchs argument än en gång, eller: vem är rädd för vetbarhetsparadoxen?In George Masterton, Keizo Matsubara & Kim Solin (eds.), Från Skaradjäkne till Uppsalaprofessor: festskrift till Lars-Göran Johansson i samband med hans pensionering, . pp. 160-171. 2017.Enligt ett realistiskt synsätt kan ett påstående vara sant trots att det inte ens i princip är möjligt att veta att det är sant. En sanningsteoretisk antirealist kan inte godta denna möjlighet utan accepterar en eller annan version av Dummetts vetbarhetsprincip: (K) Om ett påstående är sant, så måste det i princip vara möjligt att veta att det är sant. Det kan dock förefalla rimligt, även för en antirealist, att gå̊ med på̊ att det kan finnas sanningar som ingen faktiskt vet (har vetat, eller …Read more
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172A Semantic Analysis of Russellian Simple Type TheoryIn Paul Needham & Jan Odelstad (eds.), Changing Positions: Essays Dedicated to Lars Lindahl on the Occasion of His Fiftieth Birthday, Philosophical Society and the Department of Philosophy. 1986.As emphasized by Alonzo Church and David Kaplan (Church 1974, Kaplan 1975), the philosophies of language of Frege and Russell incorporate quite different methods of semantic analysis with different basic concepts and different ontologies. Accordingly we distinguish between a Fregean and a Russellian tradition in intensional semantics. The purpose of this paper is to pursue the Russellian alternative and to provide a language of intensional logic with a model-theoretic semantics. We also discuss …Read more
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46McGee's Counterexample to the Ramsey TestTheoria 83 (2): 154-168. 2017.Vann McGee has proposed a counterexample to the Ramsey Test. In the counterexample, a seemingly trustworthy source has testified that p and that if not-p, then q. If one subsequently learns not-p, then one has reason to doubt the trustworthiness of the source and so, the argument goes, one has reason to doubt the conditional asserted by the source. Since what one learns is that the antecedent of the conditional holds, these doubts are contrary to the Ramsey Test. We argue that the counterexample…Read more
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1This book brings together philosophers, mathematicians and logicians to penetrate important problems in the philosophy and foundations of mathematics. In philosophy, one has been concerned with the opposition between constructivism and classical mathematics and the different ontological and epistemological views that are reflected in this opposition. The dominant foundational framework for current mathematics is classical logic and set theory with the axiom of choice (ZFC). This framework is, ho…Read more
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1041Quine's interpretation problem and the early development of possible worlds semanticsIn Ondrey Majer (ed.), The Logica Yearbook 2000, Filosofia. 2001.In this paper, I shall consider the challenge that Quine posed in 1947 to the advocates of quantified modal logic to provide an explanation, or interpretation, of modal notions that is intuitively clear, allows “quantifying in”, and does not presuppose, mysterious, intensional entities. The modal concepts that Quine and his contemporaries, e.g. Carnap and Ruth Barcan Marcus, were primarily concerned with in the 1940’s were the notions of (broadly) logical, or analytical, necessity and possibilit…Read more
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247Føllesdal i UppsalaFilosofisk Tidskrift 8 (4). 1987.Årets Hägerströmföreläsningar i Uppsala gavs i februari av den norske filosofen Dagfinn Føllesdal. Ämnet var "Mening og Erfaring". Dagfinn Føllesdal doktorerade 1961 vid Harvard med Willard Van Quine som handledare på en avhandling om kvantifierad modallogik. Han blev internationellt känd främst för studier om Husserls fenomenologi och dess förhållande till Frege samt för sina arbeten om Quines språkfilosofi. Allt sedan 60-talet har Føllesdal delat sin tid mellan Oslouniversitetet och Stanfordun…Read more
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416An exposition and development of Kanger's early semantics for modal logicIn J. H. Fetzer & P. Humphreys (eds.), The New Theory of Reference: Kripke, Marcus, and its origins, Kluwer Academic Publishers. 1998.
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502The Ramsey test and the indexicality of conditionals: A proposed resolution of Gärdenfors' paradoxIn André Fuhrmann & Hans Rott (eds.), Logic, action, and information: essays on logic in philosophy and artificial intelligence, W. De Gruyter. 1996.
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145Logicism, intuitionism, and formalism - What has become of them? (edited book)Springer. 2008.The period in the foundations of mathematics that started in 1879 with the publication of Frege's Begriffsschrift and ended in 1931 with Gödel's Über formal unentscheidbare Sätze der Principia Mathematica und verwandter Systeme I can reasonably be called the classical period. It saw the development of three major foundational programmes: the logicism of Frege, Russell and Whitehead, the intuitionism of Brouwer, and Hilbert's formalist and proof-theoretic programme. In this period, there were als…Read more
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389On probabilistic representation of non-probabilistic belief revisionJournal of Philosophical Logic 18 (1). 1989.
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In so Many Words Philosophical Essays Dedicated to Sven Danielsson on the Occasion of His Fiftieth BirthdayPhilosophical Society and the Dept. Of Philosophy, University of Uppsala. 1989.
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316Critical Study: Jon Barwise & John Perry, Situations and Attitudes (review)Noûs (5): 743-770. 1991.The present essay is a critical study of Barwise and Perry’s book, emphasizing the logical and model-theoretical aspects of their work. I begin by presenting the authors’ criticism of the classical view of logic and semantics within the tradition of Frege, Russell and Tarski. In this connection, I discuss the so-called Frege argument (“the slingshot”). I try to show that the argument appears inconclusive, not only from a situation-theoretic perspective, but also from such alternative perspective…Read more
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24How to model relational belief revisionIn Dag Prawitz & Dag Westerståhl (eds.), Logic and Philosophy of Science in Uppsala: Papers From the 9th International Congress of Logic, Methodology and Philosophy of Science, Kluwer Academic Publishers. pp. 69--84. 1994.
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56The negative Ramsey testIn André Fuhrmann & Michael Morreau (eds.), The Logic of Theory Change: Workshop, Konstanz, FRG, October 13-15, 1989, Proceedings, Springer. 1991.The so called Ramsey test is a semantic recipe for determining whether a conditional proposition is acceptable in a given state of belief. Informally, it can be formulated as follows: (RT) Accept a proposition of the form "if A, then C" in a state of belief K, if and only if the minimal change of K needed to accept A also requires accepting C. In Gärdenfors (1986) it was shown that the Ramsey test is, in the context of some other weak conditions, on pain of triviality incompatible with th…Read more
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Formal Languages and Intensional SemanticsDissertation, Stanford University. 1981.This is a thesis in formal semantics. It consists of two parts corresponding to the distinction, due to Richard Montague, between universal grammar and specific semantic theories. The first part concerns universal grammar and is intended to provide a precise and unified conceptual framework within which different theories of formal semantics can be represented and compared. ;The second part of the thesis is concerned with intensional logic, i.e., with the logical analysis of discourse involving …Read more
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236Belief change for introspective agentsSpinning Ideas, Electronic Essays Dedicated to Peter Gärdenfors on His Fiftieth Birthday. 1999.We discuss various possibilities for developing a dynamic doxastic logic (DDL) for introspective agents: agents who have the ability to form higher-order beliefs. Such agents can reflect upon and change their minds about their own beliefs. The project of constructing such a logic, full DDL or DDL unlimited, is ridden with difficulties due to the fact that the agent's own doxastic state now becomes a part of the reality he is trying to explore. When an introspective agent learns more about the wo…Read more
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1659Modal logic and philosophyIn Patrick Blackburn, Johan van Benthem & Frank Wolter (eds.), Handbook of Modal Logic, Elsevier. pp. 1149-1214. 2006.Modal logic is one of philosophy’s many children. As a mature adult it has moved out of the parental home and is nowadays straying far from its parent. But the ties are still there: philosophy is important to modal logic, modal logic is important for philosophy. Or, at least, this is a thesis we try to defend in this chapter. Limitations of space have ruled out any attempt at writing a survey of all the work going on in our field—a book would be needed for that. Instead, we have tried to select …Read more
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Umeå UniversityRetired faculty
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Umeå UniversityResearcher (Part-time)
Uppsala, Uppsala Lan, Sweden
Areas of Specialization
Logic and Philosophy of Logic |
Philosophy of Mathematics |
Philosophy of Language |
Metaphysics and Epistemology |
Areas of Interest
General Philosophy of Science |