Imagination has recently attracted considerable attention from epistemologists and is recognized as a source of belief and even knowledge. One remarkable feature of imagination is that it is often and typically agentive: agents decide to imagine. In cases in which imagination results in a belief, the agentiveness of imagination may be taken to give rise to indirect doxastic control and epistemic responsibility. This observation calls for a proper understanding of agentive imagination. In particular, it calls for the development of a (...) semantics of imagination ascriptions. In the present paper an earlier suggestion by Ilkka Niiniluoto for a logic of imagination is considered. This proposal does not capture the agentive nature of imagination, and an alternative semantics is suggested. The new semantics combines the modal logic of agency with the neighbourhood semantics from alethic modal logic. (shrink)

Dieses Werk ist Teil der Buchreihe TREDITION CLASSICS. Der Verlag tredition aus Hamburg veroffentlicht in der Buchreihe TREDITION CLASSICS Werke aus mehr als zwei Jahrtausenden. Diese waren zu einem Grossteil vergriffen oder nur noch antiquarisch erhaltlich. Mit der Buchreihe TREDITION CLASSICS verfolgt tredition das Ziel, tausende Klassiker der Weltliteratur verschiedener Sprachen wieder als gedruckte Bucher zu verlegen - und das weltweit! Die Buchreihe dient zur Bewahrung der Literatur und Forderung der Kultur. Sie tragt so dazu bei, dass viele tausend Werke (...) nicht in Vergessenheit geraten. (shrink)

A version of strong negation is introduced into Categorial Grammar. The resulting syntactic calculi turn out to be systems of connexive logic.

Model-theoretic proofs of functional completenes along the lines of [McCullough 1971, Journal of Symbolic Logic 36, 15–20] are given for various constructive modal propositional logics with strong negation.

In this paper we elaborate a conception of entailment based on what we call the Ackermann principle, which explicates valid entailment through a logical connection between sentences depending on their informational content. We reconstruct Dunn’s informational semantics for entailment on the basis of Restall’s approach, with assertion and denial as two independent speech acts, by introducing the notion of a ‘position description’. We show how the machinery of position descriptions can effectively be used to define the positive and the negative (...) information carried by sentences of a given language and to present a formalized version of the Ackermann principle as an inclusion relationship between the informational contents of the conclusions and the premises of a valid entailment. Being so interpreted, the entailment relation exhibits certain properties, including the property of transitivity. Whereas properties such as Anderson and Belnap’s variable sharing property or Parry’s proscriptive principle are normally presented as imposing a relevance requirement on valid entailment, the suggested formalization of the Ackermann principle supports all of Gentzen’s structural rules, including weakening, a rule that is normally given up in sequent-style proof systems for relevance logics. In this way we propose an Ackermann-inspired explication of the nature of entailment as a relation between the informational contents of sentences. (shrink)

Neinsagen ist die Formel des Protestes. In einer Welt, die zu Protesten Anlaß bietet, scheint es nicht überflüssig, diese Formel zu untersuchen.

We consider a labelled tableau presentation of constant domain first-order S5 and prove a strong cut-elimination theorem.