Do Ignorant Assessors Cases Pose a Challenge to Relativism about Epistemic Modals

1.IntroductionOur ordinary conversations are filled with talk about what could or must be. For instance, in an iconic scene from On the Waterfront, the protagonist Terry bemoans his ruined boxing career. "I could have been a contender," he says, "instead of a bum, which is what I am."1 Terry's regret is tied not only to the way things are but also to the way things might have been. As it was, Terry lost his chance at the title. However, had he not thrown a big fight, things might have turned out quite differently for him. "Could" and "might," along with their duals, "should" and "must," are modal terms: we use them to talk about what is possible and what is necessary. Terry's statement has to do with what is metaphysically possible. Although certain things are essential to Terry's nature, presumably being a bum is not. T here are other kinds of possibility besides metaphysical possibility. For instance, when a parent tells a child "You must not lie," she is reminding the chi ld of what is morally necessary - that is, what is not possible given the constraints of morality.One particularly interesting type of modality is epistemic modality, which concerns what is possible given a body of knowledge or evidence. For instance, consider Luke and Max's conversation in (1).(1) Luke: What did you catch out on the lake?Max: I'm no expert, but it might be a rainbow trout.Luke: It can't be a rainbow trout. It is missing the pink streak down its side.Max: Oh, then I guess I was wrong.Cases involving epistemic modals, such as (1), present an interesting semantic challenge. In order to give a semantic treatment of epistemic modals, we must explain how informational states figure in the semantic representation of these terms. Recently, there have been several proposals for a semantic theory of epistemic modals.2 One major view - relativism -holds that claims involving epistemic modals are only true or false relative to epistemic agents or informational states. On this view, epistemic modals are quantifiers over epistemic possibilities, and the range of possibilities quantified over changes depending on whose knowledge is relevant. For now, we can think of epistemic possibilities as represented by epistemically possible worlds - worlds compatible with what is known.3 Formally, utterances containing epistemic modals express propositions (which we can think of as either sets of worlds or functions from worlds to truth values) that are evaluated for truth relative to a circumstance of evaluation (or index). The circumstance of evaluation includes a parameter i that represents an informational state that determines the range of the quantifier.Because informational states vary from person to person, an important question for the relativist to answer is "whose knowledge is relevant?" According to a basic version of relativism - call it speaker relativism - the truth of an epistemic modal claim depends upon what the speaker knows at the time of utterance. It is true just in case what the speaker knows at the time she utters the claim does not rule out the possibility in question. Relativist John MacFarlane claims that speaker relativism is inadequate. He argues that examples like (1) show that it cannot be the speaker's information that is relevant. If the speaker's evidence alone is relevant, then it would hardly be appropriate for Luke to contradict Max's claim, or for Max to retract it. After all, for all Max knew at the time he uttered the claim, the fish was a rainbow trout. Instead, MacFarlane suggests that the truth of epistemic modal claims depends on the informational state of the person assessing the claim. According to MacFarlane's view - call it assessor relativism - epistemic modal claims are assessment-sensitive in that their truth depends on what is known by the assessor at the time he or she assesses the claim. Hence, truth for epistemic modal claims varies with what MacFarlane calls the context of assessment4Examples such as (1) seem especially suited to support assessor relativism because, in this case, the assessor knows more than the speaker. …