Lewis's Semantics Research Articles

Relativity, Quantum Entanglement, Counterfactuals, and Causation

We investigate whether standard counterfactual analyses of causation (CACs) imply that the outcomes of space-like separated measurements on entangled particles are causally related. While it has sometimes been claimed that standard CACs imply such a causal relation, we argue that a careful examination of David Lewis's influential counterfactual semantics casts doubt upon this. We discuss ways in which Lewis's semantics and standard CACs might be extended to the case of space-like correlations.

Would-Cause Semantics

This article raises two difficulties that certain approaches to causation have with would-cause counterfactuals. First, there is a problem with David Lewis's semantics of counterfactuals when we ‘suppose in’ some positive event of a certain kind. And, second, there is a problem with embedded counterfactuals. I show that causal-modeling approaches do not have these problems.

On Lewis, Schaffer and the Non‐Reductive Evaluation of Counterfactuals

Abstract Jonathan Schaffer (2004) proposes an ingenious amendment to David Lewis's semantics for counterfactuals. This amendment explicitly invokes the notion of causal independence, thus giving up Lewis's ambitions for a reductive counterfactual account of causation. But in return, it rescues Lewis's semantics from extant counterexamples.I present a new counterexample that defeats even Schaffer's amendment. Further, I argue that a better approach would be to follow the causal modelling literature and evaluate counterfactuals via an explicit postulated causal structure. This alternative approach easily resolves the new counterexample, as well as all the previous ones. Up to now, its perceived drawback relative to Lewis's scheme has been its non‐reductiveness. But since the same drawback applies equally to Schaffer's amended scheme, this becomes no longer a point of comparative disadvantage.

Counterfactuals for Consequentialists

That all subjunctive conditionals with true antecedents and trueconsequents are themselves also true is implied by every plausibleand popularly endorsed account. But I am wary of endorsing thisimplication. I argue that all presently endorsed accounts fail tocapture the nature of certain subjunctive conditionals in contextsof consequentialist reasoning. I attempt to show that we must allowfor the possibility that some subjunctive conditionals with trueantecedents and true consequents are false, if we are to believethat certain types of straightforward consequentialist reasoningare coherent. I begin by evaluating a pair of morally releventcounterfactuals in a case via David Lewis's account. I then turnto a slight modification of the case, arguing that Lewis'ssemantics fails to generate the correct truth values of thesubjunctive conditionals in the modified case. Finally, I presenta modified version of Lewis's semantics that generates the correctresults in all of the cases.

Who's Afraid of Impossible Worlds?

A theory of ersatz impossible worlds is developed to deal with the problem of counterpossible conditionals. Using only tools standardly in the toolbox of possible worlds theorists, it is shown that we can construct a model for counterpossibles. This model is a natural extension of Lewis's semantics for counterfactuals, but instead of using classical logic as its base, it uses the logic LP.

David Lewis's Semantics for Deontic Logic

Numerous attempts to provide'semantic interpretations for deontic logic are based on the idea that a given state of affairs ought to be the case in this world if and only if it is the case in every morally perfect world. In classical versions of this theory, a 'morally perfect world' is simply defined as one in which all the particular obligations obtaining in the actual world are fulfilled.' Such theories have two disadvantages. First, as Richard Purtill has pointed out, it is extremely difficult to spell out the requirement that all obtaining obligations be satisfied in a morally perfect world.2 If a world contains no agents at all, are all our obligations fulfilled in it? If it contains agents who are not counterparts to the agents in this world, are our obligations fulfilled in it? Second, the value of such theories lies solely in their elucidation of the logical form of obligation statements, e.g., their explanation of what makes a set of obligation statements consistent. The application of such theories depends on prior possession of the list of true statements of particular obligations ('Jones ought to do A', 'Smith ought to do B', etc.). Since they do not offer an independent method for determining whether or not a given obligation obtains, they fail to provide illuminating reductive or eliminative definitions for statements of particular obligation. David Lewis has proposed a semantic theory which falls within this general tradition but employs an alternative definition of the morally best worlds.3 Because of this difference, his theory may escape Purtill's direct objections.4 In addition, this aspect of his theory makes possible the derivation of particular obligations, not from an initial list of such obligations, but rather from a statement of abstract moral principles together with the general notion of a possible world. Thus it may be interpreted as providing not only an account of the logical form of statements of particular obligations, but also a reductive definition of them -in terms of these other two concepts. Promising as this theory appears, I shall argue that it does not succeed, because it neglects the fact that