In this paper I argue against the commonly received view that Kripke’s formal Possible World Semantics (PWS) reflects the adoption of a metaphysical interpretation of the modal operators. I consider in detail Kripke’s three main innovations vis-à-vis Carnap’s PWS: a new view of the worlds, variable domains of quantification, and the adoption of a universal notion of validity. I argue that all t...

We present a propositional probability logic which allows making formulas that speak about imprecise and conditional probabilities. A class of Kripke-like probabilistic models is defined to give semantics to probabilistic formulas. Every possible world of such a model is equipped with a probability space. The corresponding probabilities may have nonstandard values. The proposition “the probabil...

This paper discusses how to remove a kind of ambiguity in a text understanding system based on simulation. The system simulates some events mentioned in text on a world model and observes the behavior of the model during the simulation. Through these processes, it can recognize the other events mentioned implicitly. However, in case the system infers plural number of possible world, it can't de...

In this paper, we propose a solution to McCarthy’s qualification problem [lo] based on the notion of possible worlds [3, 61. We begin by noting that existing formal solutions to qualification seem to us to suffer from serious epistemological and computational difficulties. We present a formalization of action based on the notion of possible worlds, and show that our solution to the qualificatio...

This article traces the development of possible worlds semantics through the work of: Wittgenstein, 1913–1921; Feys, 1924; McKinsey, 1945; Carnap, 1945–1947; McKinsey, Tarski and Jónsson, 1947–1952; von Wright, 1951; Becker, 1952; Prior, 1953– 1954; Montague, 1955; Meredith and Prior, 1956; Geach, 1960; Smiley, 1955–1957; Kanger, 1957; Hintikka, 1957; Guillaume, 1958; Binkley, 1958; Bayart, 195...

What sorts of properties should we use in building our conception of the way the world is? David Lewis offers one answer to this question; Robert Stalnaker offers another. Lewis suggests a reductionist picture, according to which we should strive to build our conception of the way the world is on the basis of fundamental (or ‘perfectly natural’) properties. Fundamental properties, according to ...

Approaches to belief revision most commonly deal with categorical information: an agent has a set of beliefs and the goal is to consistently incorporate a new item of information given by a formula. However, most information about the real world is not categorical. In revision, one may circumvent this fact by assuming that, in some fashion or other, an agent has elected to accept a formula φ, a...

Most belief change operators in the AGM tradition assume an underlying plausibility ordering over the possible worlds which is transitive and complete. A unifying structure for these operators, based on supplementing the plausibility ordering with a second, guiding, relation over the worlds was presented in [Booth et al., 2004]. However it is not always reasonable to assume completeness of the ...

The objective of this paper is to introduce the hybrid logic methodology into possibilistic reasoning. It has been well-known that possibilistic logic has some strong modal logic flavor. However, modal logic lacks the capability of referring to states or possible worlds though states are crucial to its semantics. Hybrid logic circumvents the problem by blending the classical logic mechanism int...

The notion of knowledge has recently acquired a great deal of importance in Computer Science, partly because of its importance in AI and expert systems, but also because of applications in distributed computing and possible, even likely relevance to cryptography. See [H2] for a representative collection of papers on knowledge. An important outstanding problem in the logic of knowledge is the pr...