Impossible Worlds - OUP

2013

"It is a venerable slogan due to David Hume, and inherited by the empiricist tradition, that the impossible cannot be believed, or even conceived. In Positivismus und Realismus, Moritz Schlick claimed that, while the merely practically impossible is still conceivable, the logically impossible, such as an explicit inconsistency, is simply unthinkable. An opposite philosophical tradition, however, maintains that inconsistencies and logical impossibilities are thinkable, and sometimes believable, too. In the Science of Logic, Hegel already complained against “one of the fundamental prejudices of logic as hitherto understood”, namely that “the contradictory cannot be imagined or thought” (Hegel 1931: 430). Our representational capabilities are not limited to the possible, for we appear to be able to imagine and describe also impossibilities — perhaps without being aware that they are impossible. Such impossibilities and inconsistencies are what this entry is about..."

In this paper, I argue for a particular conception of impossible worlds. Possible worlds, as traditionally understood, can be used in the analysis of propositions, the content of belief, the truth of counterfactuals, and so on. Yet possible worlds are not capable of differentiating propositions that are necessarily equivalent, making sense of the beliefs of agents who are not ideally rational, or giving truth values to counterfactuals with necessarily false antecedents. The addition of impossible worlds addresses these issues. The kinds of impossible worlds capable of performing this task are not mysterious sui generis entities, but sets of structured propositions that are themselves constructed out of possible worlds and relations. I also respond to a worry that these impossible worlds are unable to represent claims about the shape of modal space itself.

Australasian Journal of Logic, 2018

Review of Analytic Philosophy, 2021

As philosophers have discovered theoretical limits of intensional frameworks for analyzing philosophical phenomena, which have been partly but intimately developed along with the theories about possible worlds, the attention directed to impossible worlds as further theoretical resources has been increasing. This fact naturally provokes the ontological question: what is the nature of impossible worlds? Given the growing importance of the ontology of impossible worlds, I aim to defend the fictionalism about impossible worlds in this paper. First, I divide the positions in the ontology of impossible worlds into six kinds based on whether possible and impossible worlds are concrete, abstract, or fictional. Second, I examine each position and show that the most promising view is that impossible worlds are fictional while possible worlds are either concrete or abstract. Finally, I consider and try to accommodate possible concerns with the fictionalism about impossible worlds.

The Philosophical Quarterly, 2010

Accounts of propositions as sets of possible worlds have been criticized for conflating distinct impossible propositions. In response to this problem, some have proposed to introduce impossible worlds to represent distinct impossibilities, endorsing the thesis that impossible worlds must be of the same kind; this has been called the parity thesis. I show that this thesis faces problems, and propose a hybrid account which rejects it: possible worlds are taken as concrete Lewisian worlds, and impossibilities are represented as set-theoretic constructions out of them. This hybrid account (1) distinguishes many intuitively distinct impossible propositions; (2) identifies impossible propositions with extensional constructions; (3) avoids resorting to primitive modality, at least so far as Lewisian modal realism does.

Worlds, Possible and Impossible (Elsevier), 2024

Introduction 1 Modality 1 Applications of Possible Worlds 2 What are Possible Worlds? 2 Impossible Worlds 3 Conclusion 4 References 4 Key Points • actuality • possibility • analysis of nonemodal claims • analysis of modal claims • impossibility

This article examines the logical relationship between objects in stories and the worlds those objects imply. It argues that when confronted with an apparently impossible object one can choose to re-define its impossibility as the possibility of a new world. The article focuses on one particular impossible object, the time machine. The time machine violates not only physical but also logical laws, forcing us to choose between seeing its effects as self-contradictory – and therefore labelling the object impossible – or as paradoxical, in which case the world must be re-imagined in order to accommodate it. The article argues that Erwin Schrödinger’s well known thought experiment involving a cat that is both alive and dead, a narrative characterized by an interrogative deployment of paradox, is a useful paradigm that can help us understand how fictions about impossible events or objects pose questions about fictional worlds.

The traditional Lewis-Stalnaker semantics of counterfactuals suffers from the problem of counterpossibles: Many counterpossibles seem non-trivially true or false, but the Lewis-Stalnaker semantics deems all counterpossibles trivially true. Many proposed solutions to this problem center around the use of impossible worlds, where necessary falsehoods can be true. Ersatzists have commonly identified impossible worlds with maximal, inconsistent sets of sentences. However, Jens Christian Bjerring (2013) has recently argued that the extended Lewis-Stalnaker semantics delivers the wrong truth values for some counterpossibles if all impossible worlds are maximal. To remedy this defect, Bjerring considers two alternative world ontologies: one in which impossible worlds correspond to arbitrary (maximal or non-maximal) inconsistent sets of sentences, and another in which impossible worlds correspond to (maximal or non-maximal) sets of sentences that are deductively closed in some non-classical logic. Bjerring raises a worry about the former alternative and therefore prefers the latter. In this paper, I argue that Bjerring’s worry about the former alternative is based on a conflation of two distinct conceptions of what it means for a logic to be true in a world. I also argue that the latter alternative does not allow for impossible worlds to be sufficiently logically ill-behaved. I conclude that this tips the balance in favour of the former world ontology.

2010

Lewisian Genuine Realism (GR) about possible worlds is often deemed unable to accommodate impossible worlds and reap the benefits that these bestow to rival theories.

Any worlds semantics for intentionality has to provide a plenitudi-nous theory of impossibility: for any impossible proposition, it should provide a world where it is true. Hence, also any semantics for impossibility statements that extends Lewis's concretism about possible worlds should be plenitudinious. However, several such proposals for impossi-bilist semantics fail to accommodate two kinds of impossibility which, albeit not unheard of, have been largely neglected in the literature on impossible worlds, but which are bound to arise in the Lewisian context. The proposals discussed here (by Restall, Berto, and Kiourti) stop short of plenitude because they adhere to what Lewis occasionally referred to as " ontological truth " , as they lack the semantic ability to misrepresent ontological facts. The paper develops a framework for systematic misrep-resentations on the basis of Mares's situation-based account of impossible 'worlds', and which confines " ontological truth " to possibility. It thus illustrates how a plenitude of impossibilities can be achieved.