FILOSOFISKA NOTISER


Filosofiska Notiser Årgång 8, Nr 2, 2021


Erik Persson
Astrobiologins filosofi - Några frågor rörande teoretisk filosofi

Abstrakt
Denna artikel är den första i en serie om två artiklar som introducerar astrobiologins filosofi. Detta är ett förhållandevis nytt och i Sverige nästan okänt forskningsfält som dock befinner sig i snabb tillväxt internationellt. Ämnet presenteras här i form av exempel på några centrala frågeställningar inom området. I den här artikeln presenteras några frågeställningar hemmahörande i teoretisk filosofi.

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Erik Persson
Astrobiologins filosofi - Några frågor rörande praktisk filosofi

Abstrakt
Denna artikel är den andra i en serie om två artiklar som introducerar astrobiologins filosofi. Detta är ett förhållandevis nytt och i Sverige nästan okänt forskningsfält som dock befinner sig i snabb tillväxt internationellt. Ämnet presenteras här i form av exempel på några centrala frågeställningar inom området. I den här artikeln presenteras några frågeställningar hemmahörande i praktisk filosof.

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William Simkulet
Spontaneous Abortion and Inaction

Abstract
Pro-life theorists argue that human fetuses have moral worth from conception, or soon afterwards, and because of this induced abortion – both killing and disconnecting the fetus – is prima facie morally wrong. Evidence suggests that many more fetuses die of spontaneous abortion than induced abortion; yet many pro-life theorists act as though these fetal lives lack moral worth. Here, I evaluate the claim that inaction in the face of spontaneous abortion is morally monstrous.

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Filosofiska Notiser Årgång 8, Nr 1, 2021

This is a special issue on modal logic.


Max Cresswell
Prior and Łukasiewicz on Modal Logic

Abstract
A. N. Prior was strongly influenced by the work of Polish logicians, especially Jan Łukasiewicz. One important consequence is his adoption of Łukasiewicz's bracket-free notation for logical formulae, but he also took issue with Łukasiewicz's criticism of Aristotle's views on possibility. The present paper looks at the role of I. M. Bochenski in making Prior aware of the Polish logical tradition.

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Bas C. van Fraassen
Logic of a Self-Transparent Believer

Abstract
Moore's Paradox engendered various proposals for aspects of the logic of belief, both for believers to avoid falling into its form of incoherence and for special principles to serve as axioms or rules for doxastic logic. The proposal here developed is to study the logic pertaining to believers who are self-transparent in the sense that, although they may have many false beliefs, they are right about what their beliefs are. The logic of the language of factual description of their situation is a normal modal logic KDC4C4, but is to be distinguished from the internal logic that governs what follows from their beliefs, on pain of incoherence. The adequacy and completeness proofs for that logic show it to be, in some respects, severely non-classical.

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Lloyd Humberstone
Propositional Variables Occurring Exactly Once in Candidate Modal Axioms

Abstract
One does not often encounter a proposed axiom for extending one modal logic to another with the following feature: in the axiom in question some propositional variable (sentence letter) appears only once. Indeed, for a large range of modal logics L, which includes all normal modal logics, the sole occurrence of such a sentence letter can be replaced by a propositional truth or falsity constant, to give an arguably simpler axiom yielding the same extension of L, explaining the rarity of such ‘variable-isolating’ axioms in the literature. But the proof of this simple (and in one form or another, well-known) result – appearing here as Lemma 2.1 – is sensitive to the choice of modal primitives. It breaks down, for example, when, instead of necessity (or possibility), the sole non-Boolean primitive is taken to be noncontingency (or contingency), the main topic of Sections 0 and 4, the latter closing with a selection of the main problems left open. Between these, which we shall have occasion, inter alia, to observe that the (routine) proof of the lemma referred to (which is postponed to a final Appendix, Section 5) is also sensitive to the choice of Boolean primitives (Section 3).

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Jan Woleński
Propositional Self-Reference and Modalities

Abstract
This paper considers modal self-referential sentences and argues that they generate semantic paradoxes similar to the Liar. The sources of related antinomies are similar as in the case of the Liar-sentence, namely self-referentiality and the T-scheme, additionally supplemented by some principles connecting modalities and truth. In the Appendix at the end of the paper, the dual logic is employed for constructing the Truth-Teller Paradox and its modal counterparts.

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Giovanna Corsi and Eugenio Orlandelli
FOIL with constant domains revisited

Abstract
FOIL is a family of two-sorted first-order modal logics containing both object and intensional variables. Intensional variables are represented by partial functions from worlds to objects and the abstraction operator λ is used to talk about the object (if any) denoted by an intension in a given world. This paper answers a problem left open in Fitting’s [4] by showing that Fitting’s axiomatization of FOIL augmented with infinitely many inductively defined rules, CD(k), k ≥ 0, allows for the construction of a canonical model that is essentially a constant domains model. Moreover, it is shown that the rules CD(k) are derivable in logics where the symmetry axiom B holds. Hence, Fitting’s axiomatisation of FOIL is already complete when the underlying logic imposes symmetric models.

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Andreas Herzig and Elise Perrotin
True Belief and Mere Belief About a Proposition and the Classification of Epistemic-Doxastic Situations

Abstract
Starting from standard logics of knowledge and belief with principles such as introspection of beliefs and ‘knowledge implies belief’, we study two non-normal modalities of belief: true belief about a proposition and what we call mere belief about a proposition. We show that these modalities suffice to define all possible epistemic-doxastic situations in a combinatorial manner. Furthermore, we show that two consecutive modalities that are indexed by the same agent can be reduced for two of the three logics of knowledge and belief that we consider.

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Valentin Goranko
On relative ignorance

Abstract
I discuss relative ignorance of an agent with respect to the knowledge or ignorance of other agents. It turns out, not surprisingly, that even the two-agent case is quite complex and generates a rich variety of naturally arising non-equivalent operators of relative ignorance. In this paper I explore these in a more systematic way and put together several simple, though technically laborious, observations about their inter-relations. For the technical proofs of these I employ the software tool MOLTAP, which implements, inter alia, tableaux for the underlying multi-agent epistemic logic.

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