From Possible to Impossible Worlds

2019 ◽  
pp. 11-40 ◽  
Author(s):  
Francesco Berto ◽  
Mark Jago
Keyword(s):  
Possible Worlds ◽  
Information Overload ◽  
Impossible Worlds ◽  
Logical Omniscience ◽  
Possible Worlds Semantics ◽  
Counterfactual Conditionals ◽  
General Issue

Possible worlds are ways things might have been. They find applications in analysing possibility and necessity; propositions; knowledge and belief; information; and indicative and counterfactual conditionals. But possible worlds semantics faces the issue of hyperintensionality, generated by concepts that require distinctions between logical or necessary equivalents. The problems of distinguishing equivalent propositions, of logical omniscience, of information overload, of irrelevant conditionals, and of counterpossible conditionals, are all instances of the general issue. Adding impossible worlds promises to help with these puzzles. But can we genuinely think about the impossible? It is argued that we can.

scholarly journals QUANTIFIED LOGIC OF AWARENESS AND IMPOSSIBLE POSSIBLE WORLDS

2008 ◽  
Vol 1 (4) ◽  
pp. 514-529 ◽  
Author(s):  
GIACOMO SILLARI
Keyword(s):  
Possible Worlds ◽  
Explicit Knowledge ◽  
Impossible Worlds ◽  
Kripke Semantics ◽  
Logical Omniscience ◽  
Neighborhood Semantics ◽  
Two Systems ◽  
The Many ◽  
Implicit And Explicit

Among the many possible approaches to dealing with logical omniscience, I consider here awareness and impossible worlds structures. The former approach, pioneered by Fagin and Halpern, distinguishes between implicit and explicit knowledge, and avoids logical omniscience with respect to explicit knowledge. The latter, developed by Rantala and by Hintikka, allows for the existence of logically impossible worlds to which the agents are taken to have “epistemological” access; since such worlds need not behave consistently, the agents’ knowledge is fallible relative to logical omniscience. The two approaches are known to be equally expressive in propositional systems interpreted over Kripke semantics. In this paper I show that the two approaches are equally expressive in propositional systems interpreted over Montague-Scott (neighborhood) semantics. Furthermore, I provide predicate systems of both awareness and impossible worlds structures interpreted on neighborhood semantics and prove the two systems to be equally expressive.

Meaning, Modality, and Possible Worlds Semantics

2010 ◽  
Author(s):  
Scott Soames
Keyword(s):  
Natural Language ◽  
Classical Logic ◽  
Possible Worlds ◽  
David Lewis ◽  
Formal Languages ◽  
Possible Worlds Semantics ◽  
Natural Languages ◽  
Counterfactual Conditionals ◽  
Richard Montague ◽  
Close Parallel

This chapter begins with a discussion of Kripke-style possible worlds semantics. It considers one of the most important applications of possible worlds semantics, the account of counterfactual conditionals given in Robert Stalnaker and David Lewis. It then goes on to examine the work of Richard Montague. Montague specified syntactic rules that generate English, or English-like, structures directly, while pairing each such rule with a truth-theoretic rule interpreting it. This close parallel between syntax and semantics is what makes the languages of classical logic so transparently tractable, and what they were designed to embody. Montague's bold contention is that we do not have to replace natural language natural languages with formal substitutes to achieve such transparency. The same techniques employed to create formal languages can be used to describe natural languages in mathematically revealing ways.

Epistemic Logics

2019 ◽  
pp. 107-124
Author(s):  
Francesco Berto ◽  
Mark Jago
Keyword(s):  
Epistemic Logic ◽  
Classical Logic ◽  
Possible Worlds ◽  
Impossible Worlds ◽  
Logical Omniscience ◽  
Epistemic States ◽  
Deep Problem

Standard possible-worlds epistemic logic gives rise to the problem of logical omniscience. There are attempts to deal with the problem without using impossible worlds. A number of these approaches are discussed in this chapter and all are found wanting. The impossible worlds approach is immediately more successful, but faces a deep problem: how should impossible worlds be constrained, so as to give adequate models of knowledge and belief? One option is to take impossible worlds to be closed under some weaker-than-classical logic. But this approach does not genuinely solve the problem of logical omniscience. A different approach is the dynamic one, whereby epistemic states are not closed at any one time, but nevertheless evolve towards closure in a dynamic way.

Resurgent Powers and the Failure of Conceptual Analysis

2021 ◽  
pp. 241-270
Author(s):  
Jennifer McKitrick
Keyword(s):  
Twentieth Century ◽  
Conceptual Analysis ◽  
Possible Worlds ◽  
Natural Kinds ◽  
Laws Of Nature ◽  
Counterfactual Analysis ◽  
Possible Worlds Semantics ◽  
Moderate Reaction ◽  
Counterfactual Conditionals ◽  
Scientific Discourses

Jennifer McKitrick examines the causes moving many philosophers to pull Aristotelian powers out of history’s dustbin, the failure to reduce or eliminate dispositional ascriptions from philosophical and scientific discourses. Although many see this failure as grounds for rejecting Humeanism and return to Aristotelianism, McKitrick argues that only a more moderate reaction is warranted. She argues that restricting analysis to fundamental dispositions and adding a condition requiring the power ascription be grounded in or made true by the fact that the object possesses that fundamental disposition is the better reaction. McKitrick canvasses the main twentieth-century attempts to reduce or eliminate dispositional talk. She begins with the logical positivists’ attempt to replace dispositional talk with material conditionals. Then, after briefly considering Ryle’s version, she turns to Goodman and the move to replace material conditional analyses with stronger-than-material conditionals, such as causal implication or counterfactual conditionals backed up by natural kinds and laws of nature. Next, she turns to Lewis’s possible worlds semantics and concludes with a presentation of the ‘Simple Counterfactual Analysis’. Despite these problems with providing analyses of dispositional ascriptions in terms of counterfactuals, McKitrick recognizes that there is still an important connection between dispositions and counterfactuals. A thing’s disposition is its property of having a certain kind of counterfactual hold of it. But she advocates restricting counterfactual analyses to fundamental dispositions and powers and requiring that they be made true, or grounded by, the fact that the object has that power.

The Failure of Conceptual Analysis

2018 ◽  
Author(s):  
Jennifer McKitrick
Keyword(s):  
Conceptual Analysis ◽  
Possible Worlds ◽  
Causal Power ◽  
Possible Worlds Semantics ◽  
Conditional Statements ◽  
Reductive Analysis

Dispositions are often regarded with suspicion. Consequently, some philosophers try to semantically reduce disposition ascriptions to sentences containing only non-dispositional vocabulary. Typically, reductionists attempt to analyze disposition ascriptions in terms of conditional statements. These conditional statements, like other modal claims, are often interpreted in terms of possible worlds semantics. However, conditional analyses are subject to a number of problems and counterexamples, including random coincidences, void satisfaction, masks, antidotes, mimics, altering, and finks. Some analyses fail to reduce disposition ascriptions to non-modal vocabulary. If reductive analysis of disposition ascriptions fails, then perhaps there can be metaphysical reduction of dispositions without semantic reduction. However, the reductionist still owes us an account of what makes disposition ascriptions true. But to posit a causal power for every unreduced dispositional predicate is an overreaction to the failure of conceptual analysis.

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