Counterfactuals and Knowledge

The uploaded document contains my PhD dissertation. The abstract is given below. ABSTRACT The two main features of this thesis are (i) an account of contextualized (context indexed) counterfactuals, and (ii) a non-vacuist account of counterpossibles. Experience tells us that the truth of the counterfactual is contingent on what is meant by the antecedent, which in turn rests on what context is assumed to underlie its reading (intended meaning). On most conditional analyses, only the world of evaluation and the antecedent determine which worlds are relevant to determining the truth of a conditional, and consequently what its truth value is. But that results in the underlying context being fixed, when evaluating distinct counterfactuals with the same antecedent on any single occasion, even when the context underlying the evaluation of each counterfactual may vary. Alternative approaches go some of the way toward resolving this inadequacy by appealing to a difference in the consequents associated with counterfactuals with the same antecedent. That is, in addition to the world of evaluation and the antecedent, the consequent contributes to the counterfactual’s evaluation. But these alternative approaches nevertheless give a single, determinate truth value to any single conditional (same antecedent and consequent), despite the possibility that this value may vary with context. My reply to these shortcomings (chapter 4) takes the form of an analysis of a language that makes appropriate explicit access to the intended context available. That is, I give an account of a contextualized counterfactual of the form ‘In context C: If it were the case that … , then it would be the case that …’. Although my proposal is largely based on Lewis’ (1973, 1981) analyses of counterfactuals (the logic VW and its ordering semantics), it does not require that any particular logic of counterfactuals should serve as its basis – rather, it is a general prescription for contextualizing a conditional language. The advantage of working with ordering semantics stems from existing results (which I apply and develop) concerning the properties of ordering frames that facilitate fashioning and implementing a notion of contextual information preservation. Analyses of counterfactuals, such as Lewis’ (1973), that cash out the truth of counterfactuals in terms of the corresponding material conditional’s truth at possible worlds result in all counterpossibles being evaluated as vacuously true. This is because antecedents of counterpossibles are not true at any possible world, by definition. Such vacuist analyses have already been identified and challenged by a number of authors. I join this critical front, and drawing on existing proposals, I develop an impossible world semantics for a non-vacuist account of counterpossibles (chapter 5), by modifying the same system and semantics that serve the basis of the contextualized account offered in chapter 4, i.e. Lewis’ (1986) ordering semantics for the logic VW. I critically evaluate the advantages and disadvantages of key conditions on the ordering of worlds on the extended domain and show that there is a sense in which all of Lewis’ analysis of mere counterfactuals can be preserved, whilst offering an analysis of counterpossibles that meets our intuitions. The first part of chapter 1 consists of an outline of the usefulness of impossible worlds across philosophical analyses and logic. That outline in conjunction with a critical evaluation of Lewis’ logical arguments in favour of vacuism in chapter 2, and his marvellous mountain argument against impossible worlds in chapter 3, serves to motivate and justify the impossible world semantics for counterpossibles proposed in chapter 5. The second part of chapter 1 discusses the limitations that various conditional logics face when tasked to give an adequate treatment of the influence of context. That introductory discussion in conjunction with an overview of conditional logics and their various semantics in chapter 2 – which includes an in-depth exposition of Stalnaker-Lewis similarity semantics for counterfactuals – serves as the motivation and conceptual basis for the contextualized account of counterfactuals proposed in chapter 4. - - - - - - - - - - - - - - - - (Perhaps it is worth emphasizing that the most original work is contained in chapter 4, where I give an account of a contextualized (context relativized) counterfactual of the form ‘In context C: If it were the case that … , then it would be the case that …’, based on Lewis’ (1974, 1981) analysis of the counterfactual. Drawing on earlier work by Lewis (1973, 1981) I first give an ordering semantics for counterfactuals, based on the idea of comparative similarity, interpreted as ‘similarity in relevant respects’ or as ‘relevant similarity’, and modelled by total preorderings of possible worlds. Subsequently, building on that analysis I develop model-theoretic methods for a semantic consequence relation of contextualized counterfactuals (contextualized validity), which is given as the culminating item of the chapter.)

Analysis, 2008

Journal of Philosophy, 109(3), pp. 221-46 (2012)

Synthese, 1994

In this paper I explore the ambiguity that arises between two readings of the counterfactual construction, the n-d and the l-p, analyzed in my book A Theory of Counterfactuals. I then extend the analysis I offered there to counterfactuals with true antecedents, and offer a more precise formulation of the conception of temporal divergence points used in the 1-p interpretation. Finally, i discuss some ramifications of these issues for counterfactual analyses of knowledge. t. B A C K G R O U N D In A Theory of Counterfactuals 1 (henceforth: A TC) I discussed the two major counterfactual interpretations, the n-d and the l-p. The first applies to counterfactuals, the antecedents of which are compatible with their prior histories; the second to counterfactuals whose antecedents are incompatible with their prior histories. Together they cover counterfactuals, with premises that are factual (non-nomic), false, and logically, n , m , logically, and metaphysically possible. 2 These two are by far the most prevalent kinds of counterfactual interpretations: all counterfactuals which are not covered by these two are either esoteric or parasitic on counterfactuals which are covered by these two. (Some types of such esoteric or parasitic counterfactuals are also discussed in A TC3). After a brief survey of the n-d and t-p interpretations, I will elaborate further on the l-p interpretation and then pursue the ambiguity the two interpretations generate.

Theoretical Linguistics, 2021

The analysis of counterfactuality needs a good shake-up. Wolfgang Klein's article does an excellent job in pointing out what is stale and unproductive in the literature, often inherited from philosophical discussions with limited linguistic relevance. And he posits a fresh alternative that is closer to the linguistic facts, especially as we know them from English and other Germanic languages. In this response we discuss three points that, we believe, are compatible with Klein's proposal but may bring it even closer to the linguistic facts, including for languages not discussed in Klein's paper. Apart from English, the data we use mainly come from our work on Australian languages (Verstraete 2005a, 2006, Luk in preparation), but also from a study of a broader cross-linguistic sample (Van linden & Verstraete 2008). 1. Polarity reversal rather than truth or falsity Much of the discussion of counterfactuality is framed in terms of truth or falsity (like the term itself, in fact), as inherited from work in logic and adjacent areas of philosophy. Klein's target article nicely points out that there are problems with this approach: neither counterfactual protases nor apodoses have to be 'contrary to the facts', as demonstrated by his examples (4) and (5). Instead, Klein proposes an analysis in terms of the relation between actual and nonactual worlds: a counterfactual protasis introduces a world that is not the actual one but otherwise warranted as the actual one. Under this analysis, the default interpretation of this type of protasis as 'contrary to the facts' comes from the fact that not talking about the actual world typically has a reason, the most obvious one being "that nothing can be said about the actual world" (p. 26). But this does not preclude that the situation in the protasis could also apply to the actual world, as in Klein's example (4). The last part of this argument is somewhat similar in spirit to Gricean approaches to counterfactuals (Ziegeler 2000, Verstraete 2005a, Van linden & Verstraete 2008), which state that in a 'knowable' domain like the past, using a modalized expression (e.g. X would have Yed) is less informative than using its bare counterpart (X Yed), and thus triggers the quantity-based implicature that 'X Yed' does not apply, i.e. 'X did not Y'. As an implicature, however, this can be cancelled and is thus not an inherent part of the semantics of counterfactuals, just as Klein shows for his (4).