2.5 Information-Sensitivity
2.5.1 The Phenomenon
An information-state is usually considered to be a set of worlds (Kolodny and MacFarlane 2010: 130). Alternatively, information-states could be modelled as probability distributions over propositions, as suggested by, for example, Yalcin (2011: 299) and Wedgwood (forthcoming: sec. 3). As I use the term ‘information-
state’, an information-states can represent a subject’s or a collective’s body of evidence, but can also just represent all facts, which might not be anybody’s evidence (or only God’s).
The idea that the deontic ‘should’ is information-sensitive amounts on a contextualist treatment of this phenomenon to the claim that sentences of the form ‘S should doA’ roughly mean ‘in light of information-state i,S should do
A’, where i is provided by the context in which the sentence is uttered. That is, there is no such thing as what one should dosimpliciter, but only what one should do in light of an information-state. Furthermore, there must be at least two information-statesi1 andi2 which are such that at least one instance of ‘S
should doA’ is true in light ofi1, but false in light ofi2 (Kolodny and MacFarlane
2010: 133). Finally, for the deontic ‘should’ to be fully information-sensitive, there also have to be at least two contexts that provide these two information-statesi1
andi2. Otherwise, it would only be possible, but never actually occur, that an
context of utterance. In the following, ‘information-sensitivity’ always means full information-sensitivity.
Before moving on to particular instances of information-sensitivity, it needs to be pointed out that the phenomenon need not be modelled by contextualist semantics. Kolodny and MacFarlane (2010) and in particular MacFarlane (2014: ch. 11) propose a relativist semantics for the deontic ‘should’, which captures its information-sensitivity as follows. Sentences of the form ‘S should doA’ are not true simpliciter, but only relative to so-called ‘contexts of assessment’. A context of assessment is, as the name suggests, a context from which a sentence is truth-evaluated, which is often not the same context as the one in which it was uttered, as when I evaluate a sentence you uttered. One of the contextual parameters of contexts of assessments are information-states. ‘S should doA’ can hence be true relative to one context of assessment, but false relative to another. The main differences between contextualist and relativist semantics of the deontic ‘should’ with respect to information-sensitivity are accordingly the fol- lowing two: First, contextualism entails that ‘S should do A’ expresses different propositions when uttered at two contexts with two different information-states
i1 andi2. In the first context, it means ‘S should doA in light of i1’ and in the
second ‘S should do Ain light ofi2’. According to relativism, the sentence always
expresses the same proposition. Second, for contextualists, if ‘S should doA’ is uttered in a context, it is true or falsesimpliciter. For relativists, it is only true or false relative to contexts of assessment. In the remainder of this chapter, and in fact in chapters 3 to 6 as well, I will only discuss information-sensitivity through the lense of contextualism. I will return to relativism in chapter 7. Besides relativism, a dynamic semantics of the deontic ‘should’ can also give an account of its information-sensitivity (Willer forthcoming: sec. 3.2). As explained above, I ignore dynamic semantics in this thesis for reasons of scope.
Let’s move on to particular instances of information-sensitivity. The distinction between the subjective and the objective ‘should’, as it is often made in ethics7 and also by some authors in epistemology8, can be seen as one. What a subject
S should do in the objective sense of ‘should’ is what S should do in light of
7See Ross (1939), Prichard (1932), Ewing (1953), Brandt (1963), Jackson (1986), and Parfit
(2011).
the relevant facts, and what S should do in the subjective sense, is what S
should do in light of their evidence. The subjective and the objective ‘should’ can accordingly be seen as results of relativizing the deontic ‘should’ to different information-states.9
In the recent literature on the semantics for the deontic ‘should’, it has been pointed out that we also sometimes talk about what others should do in light of our collective evidence, i.e., their and our joint evidence.10 Such occasions seem
to arise when we’re giving advice. Here is a much discussed example:
Miners.11 Ten miners are trapped either in shaft 1 or in shaft 2. Floodwaters threaten to flood the shafts. Sean has enough sandbags to block one shaft, but not both. If Sean blocks one shaft, all the water will go into the other shaft, killing any miners inside it. If Sean blocks neither shaft, both shafts will fill halfway with water, and just one miner, the lowest in the shaft where the miners are, will be killed. Sean does not know in which shaft the miners are. He says:
(8) I should block neither shaft.
A physicist, who knows that the miners are in shaft 1, hears this and says to Sean:
(9) No, you should block shaft 1.
Intuitively, (8) and (9) are both correct. One way to explain this is that (8) is true since in light of Sean’s evidence, he should block neither shaft, and that (9) is true since in light of Sean’s and the physicist’s collective evidence, Sean should block shaft 1. Since the physicist is giving advice, she’s not talking about what Sean should do in light of just his evidence, but rather what he should do in light of their combined evidence, which includes her better-informed evidence.12
9
For more on this, see chapter 3.
10See Kolodny and MacFarlane (2010), Bj¨ornsson and Finlay (2010), and Dowell (2013). 11
This case is introduced to the current debate about the information-sensitivity of deontic modals by Kolodny and MacFarlane (2010). They credit Parfit (ms) and Regan (1980).
12
In chapter 5, I will argue that in advice cases like this, the advisee, here Sean, is actually also talking to the collective evidence, and that (8) is false. This does not undermine that there is a subjective ‘should’ as there are other cases where speakers talk relative to the subject’s evidence. See, for example,Miners-CCTVin subsection 2.5.3 andNostalgiain subsection 2.6.2 below.
If this is the accurate explanation of the meaning of (9), Miners is a case in which ‘should’ is neither subjective nor objective, but relativized to the collective evidence. Contextualism brings order to this “profusion” (Jackson 1991: 471) of ‘should’s. It models them as different instances of one lexical entry for ‘should’,
which result from ‘should’ being relativized to different contextually provided information-states.
Many authors argue that a specific theory capturing the information-sensitivity of ‘should’ is needed since Kratzer’s standard account of modals, in its original version, cannot do this.13 The ordering sourcegis realistic in that it ranks worlds in light of the facts, not in light of some agent’s less-than-omniscient information- state. For example, the standard Kratzerian ordering source in the context of Sean’s utterance ranks the worlds in the modal background relative to an ordering background containing the proposition<All miners are saved>14.15 Worlds where Sean blocks the shaft in which the miners are are closer to this ideal than worlds where Sean blocks neither shaft. Thus, it is not true in all the best-ranked worlds that Sean blocks neither shaft. It follows that Kratzer’s theory can’t account for the truth of (8).
One might think that one could model information-sensitivity in Kratzer’s semantics by assuming that the modal base of an information-sensitive ‘should’ is epistemic, not circumstantial. That is, rather than containing all the worlds compatible with a certain realistic, i.e., true, description of how the world is in relevant features (e.g., that the miners are in shaft 1), it contains all the worlds compatible with what the speaker knows. This way, we can get the subject’s information-state to play a role in the truth-conditions of a sentence containing ‘should’, at least where the subject is also the speaker, as in the case of (8).
However, this won’t get the results we need. The set of worlds compatible with what Sean knows contain both worlds where the miners are in shaft 1 and where they are in shaft 2. The worlds where the miners are in shaft 1 and Sean blocks shaft 1 and those where they are in shaft 2 and Sean blocks shaft 2 will be higher
13
See Dowell (2013: 150), Cariani et al. (2013: 244), and Charlow (2013: 2303). For an objection to this, see Silk (2014: 709).
14
Throughout this thesis, I use angle brackets to mark propositions.
15I’m ignoring here the additional complexities arising from modifying Kratzer’s theory of
‘must’ so that it works for ‘should’. Even when they are accounted for, the point about Kratzerian ordering sources being realistic stands.
ranked than those where he blocks neither shaft, since in the former kinds of worlds he saves 10 miners, where in the latter only 9. Thus, making the modal base epistemic rather than circumstantial won’t help (Cariani et al. 2013: 235).