The fundamental principle of the theory of possible worlds is that a proposition p is possible if and only if there is a possible world at which p is true. In this paper we present a valid derivation of this principle from a more general theory in which possible worlds are defined rather than taken as primitive. The general theory uses a primitive modality and axiomatizes abstract objects, prop...

We consider two approaches to giving semantics to first order logics of probability. The first approach puts a probability on the domain, and is appropriate for giving semantics to formulas involving statistical information such as "The probability that a (typical) bird flies is greater than .9." The second approach puts a probability on possible worlds, and is appropriate for giving semantics ...

This paper introduces conceptual relations tlrat syntlresizc utilitarian and logical con­ cepts, extending the logics of preference of [{escher. We define first, in the context of a possible­ worlds modeL constraint-dependent mea­ sures that quantify the relative quality of al­ temative solutions of reasoning problems or the relative desirabi lity of various policies in coutrol. decision, and p...

Many merging operators have been proposed to merge either flat or stratified knowledge bases. The result of merging by such an operator is a flat base (or a set of models of the merged base) irrespective of whether the original ones are flat or stratified. The drawback of obtaining a flat merged base is that information about more preferred knowledge (formulae) versus less preferred knowledge i...

For the last thirty years, it has been assumed that a presupposition must be entailed (or ‘satisfied’) by the context, construed as what is common belief between the speaker and addressee: John has stopped smoking is acceptable in a context C just in case C entails that John used to smoke. Technically, the context in this sense is often called the ‘context set’, identified with the set of possi...

We formulate a model for reasoning about actions , knowledge and control in the presence of incomplete information and sensing operations. In the model, actions can be non-deterministic, sensors can report the value of either symbols, terms or formulas, and knowledge is constructively deened in terms of observations. The model is related to possible worlds accounts of actions and knowledge but ...

Events and possible worlds from physical systems States and observables of physical systems provide a very general source of continuously valued events and possible worlds. Let be a “physical system”. Following [6, pp.362–369], a rigorous account of is given by its associated C -algebra , with the set sa of selfadjoint elements, and the set sa of real-valued normalized positive linear functiona...

In order to avoid the paradoxes of standard deontic logic, we have to give up the semantic construction that identifies obligatory status with presence in all elements of a subset of the set of possible worlds. It is proposed that deontic logic should instead be based on a preference relation, according to the principle that whatever is better than something permitted is itself permitted. Close...

What does it mean that certain properties globally supervene on others? The paper criticises the now standard way of spelling out the notion in terms of 1-1 correlations between world-domains and proposes a modification that escapes the difficulties. The new definition can secure the additional benefit of resisting an argument to the effect that global supervenience is theoretically dispensable...