On Hume’s account of motivation, beliefs and desires are very di¤erent kinds of propositional attitudes. Beliefs are cognitive attitudes, desires emotive ones. An agent’s belief in a proposition captures the weight he or she assigns to this proposition in his or her cognitive representation of the world. An agent’s desire for a proposition captures the degree to which he or she prefers its truth, motivating him or her to act accordingly. Although beliefs and desires are sometimes entangled, they play very (...) di¤erent roles in rational agency.1 In two classic papers (Lewis 1988, 1996), David Lewis discusses several challenges to this Humean picture, but ultimately rejects them. We think that his discussion of a central anti-Humean alternative – the desire-as-belief thesis – is in need of re…nement. On this thesis, the desire for proposition p is given by the belief that p is desirable. Lewis claims that ‘[e]xcept in trivial cases, [this thesis] collapses into contradiction’(Lewis 1996, p. 308). The problem, he argues, is that the thesis is inconsistent with the purportedly plausible requirement that one’s desire for a proposition should not change upon learning that the proposition is true; call this the invariance requirement. In this paper, we revisit Lewis’s argument. We show that, if one carefully distinguishes between non-evaluative and evaluative propositions, the desire-asbelief thesis can be rendered consistent with the invariance requirement. Lewis’s conclusion holds only under certain conditions: the desire-as-belief thesis con- ‡icts with the invariance requirement if and only if there are certain correlations between non-evaluative and evaluative propositions. But when there are such correlations, we suggest, the invariance requirement loses its plausibility. Thus Lewis’s argument against the desire-as-belief thesis appears to be valid only in cases in which it is unsound. (shrink)

What we believe depends on more than the purely intrinsic facts about us: facts about our environment or context also help determine the contents of our beliefs. 1 This observation has led several writers to hope that beliefs can be divided, as it were, into two components: a "core" that depends only on the individual?s intrinsic properties; and a periphery that depends on the individual?s context, including his or her history, environment, and linguistic community. Thus Jaegwon Kim suggests that "within (...) each noninternal psychological state that enters into the explanation of some action or behavior we can locate an ?internal core state? which can assume the causal-explanatory role of the noninternal state."2 In the same vein, Stephen Stich writes that "nonautonomous" states, like belief, are best viewed as "conceptually complex hybrids" made up of an autonomous component together with historical and contextual features.3 John Perry, whose term I have adopted, distinguishes between belief states, which are determined by an individual?s intrinsic properties, and objects of belief, which are not.4 And Daniel Dennett makes use of the same notion when he asks:5. (shrink)

David Lewis claims that a simple sort of anti-Humeanism-that the rational agent desires something to the extent he believes it to be good-can be given a decision-theoretic formulation, which Lewis calls 'Desire as Belief' (DAB). Given the (widely held) assumption that Jeffrey conditionalising is a rationally permissible way to change one's mind in the face of new evidence, Lewis proves that DAB leads to absurdity. Thus, according to Lewis, the simple form of anti-Humeanism stands refuted. In this paper we investigate (...) whether Lewis's case against DAB can be strengthened by examining how it fares under rival versions of decision theory, including other conceptions of rational ways to change one's mind. We argue that the anti-Humean may escape Lewis's argument either by adopting a version of causal decision theory, or by claiming that the refutation only applies to hyper-idealised rational agents, or by denying that the decision-theoretic framework has the expressive capacity to formulate anti-Humeanism. (shrink)

Rationalizations of deliberation often make reference to two kinds of mental state, which we call belief and desire. It is worth asking whether these kinds are necessarily distinct, or whether it might be possible to construe desire as belief of a certain sort — belief, say, about what would be good. An expected value theory formalizes our notions of belief and desire, treating each as a matter of degree. In this context the thesis that desire is belief might amount to (...) the claim that the degree to which an agent desires any proposition A equals the degree to which the agent believes the proposition that A would be good. We shall write this latter proposition ‘A◦’ (pronounced ‘A halo’). The Desire-as-Belief Thesis states, then, that to each proposition A there corresponds another proposition A◦, where the probability of A◦ equals the expected value of A. (shrink)

I show the incompatibility of two theses: (a) to desire the truth of p amounts to believing a certain proposition about the value of p’s truth; (b) one cannot be said to desire the truth of p if one believes that p is true. Thesis (a), the Desire-As-Belief Thesis, has received much attention since the late 1980s. Thesis (b) is an epistemic variant of Socrates’ remark in the Symposium that one cannot desire what one already has. It turns out that (...) (a) and (b) cannot both be true if it is possible for there to exist an agent who has a desire initially, say the desire for the truth of p, and then expands the corpus of propositions she believes to include p. This result provides a new route to the denial of (a). (shrink)

In “Desire as Belief” and “Desire as Belief II,” David Lewis ( 1988 , 1996 ) considers the anti-Humean position that beliefs about the good require corresponding desires, which is his way of understanding the idea that beliefs about the good are capable of motivating behavior. He translates this anti-Humean claim into decision theoretic terms and demonstrates that it leads to absurdity and contradiction. As Ruth Weintraub ( 2007 ) has shown, Lewis’ argument goes awry at the outset. His decision (...) theoretic formulation of anti-Humeanism is one that no sensible anti-Humean would endorse. My aim is to demonstrate that Lewis’ infelicitous rendering of anti-Humeanism really does undermine the force of his arguments. To accomplish this, I begin by developing a more adequate decision theoretic rendering of the anti-Humean position. After showing that my formulation of anti-Humeanism constitutes a plausible interpretation of the anti-Humean thesis, I go on to demonstrate that if we adopt this more accurate rendition of anti-Humeanism, the view is no longer susceptible to arguments like the ones Lewis has devised. I thereby provide a more robust response to Lewis’ arguments than has yet been offered, and in the process I develop a formulation of anti-Humeanism that creates the possibility for future decision theoretic arguments that, unlike Lewis’, speak directly to the plausibility of anti-Humeanism. (shrink)

David Lewis [1988; 1996] canvases an anti-Humean thesis about mental states: that the rational agent desires something to the extent that he or she believes it to be good. Lewis offers and refutes a decision-theoretic formulation of it, the `Desire-as- Belief Thesis'. Other authors have since added further negative results in the spirit of Lewis's. We explore ways of being anti-Humean that evade all these negative results. We begin by providing background on evidential decision theory and on Lewis's negative results. (...) We then introduce what we call the indexicality loophole: if the goodness of a proposition is indexical, partly a function of an agent's mental state, then the negative results have no purchase. Thus we propose a variant of Desire-as- Belief that exploits this loophole. We argue that a number of meta-ethical positions are committed to just such indexicality. Indeed, we show that with one central sort of evaluative beliefÐthe belief that an option is rightÐthe indexicality loophole can be exploited in various interesting ways. Moreover, on some accounts, `good' is indexical in the same way. Thus, it seems that the anti-Humean can dodge the negative results. (shrink)

David Lewis [1988; 1996] canvases an anti-Humean thesis about mental states: that the rational agent desires something to the extent that he or she believes it to be good. Lewis offers and refutes a decision-theoretic formulation of it, the 'Desire-as-Belief Thesis'. Other authors have since added further negative results in the spirit of Lewis's. We explore ways of being anti-Humean that evade all these negative results. We begin by providing background on evidential decision theory and on Lewis's negative results. We (...) then introduce what we call the indexicality loophole: if the goodness of a proposition is indexical, partly a function of an agent's mental state, then the negative results have no purchase. Thus we propose a variant of Desire-as-Belief that exploits this loophole. We argue that a number of meta-ethical positions are committed to just such indexicality. Indeed, we show that with one central sort of evaluative belief--the belief that an option is right--the indexicality loophole can be exploited in various interesting ways. Moreover, on some accounts, 'good' is indexical in the same way. Thus, it seems that the anti-Humean can dodge the negative results. (shrink)

Bryne & H´ajek (1997) argue that Lewis’s (1988; 1996) objections to identifying desire with belief do not go through if our notion of desire is ‘causalized’ (characterized by causal, rather than evidential, decision theory). I argue that versions of the argument go through on certain assumptions about the formulation of decision theory. There is one version of causal decision theory where the original arguments cannot be formulated—the ‘imaging’ formulation that Joyce (1999) advocates. But I argue this formulation is independently objectionable. (...) If we want to maintain the desire as belief thesis, there’s no shortcut through causalization. (shrink)