Epistemic counterpart semantics
I have decided to write a series of posts on epistemic applications of counterpart semantics, mostly to organise my own thoughts.
Let's start with a motivating example, from Sæbø 2015.
On September 14 2006, Mary Beth Harshbarger shot her husband, whom she had mistaken for a bear. At the trial, she "steadily maintained that she thought her husband was a black bear", as you can read on Wikipedia.
We're interested in this sentence: "Mary thought her husband was a bear."
The sentence has two readings. On its de dicto reading, it says that Mary thought that she was married to a bear. It is safe to assume that this is not what Mary Harshbarger meant at the trial. The intended reading is de re. On this reading, the sentence says that Mary thought of her husband that he was a bear.
But what, exactly, does this mean?
A simple and popular answer is that the de re reading attributes to Mary a thought whose content is a singular proposition directly involving her husband (Mark).
Let's call this the direct interpretation of the (de re) attitude report. It leads to some well-known problems, of which I'll mention two.
First, Mary Harshbarger presumably knew a lot about her husband Mark. Among other things, she knew that he has a brother, and that he was human. So she believed of her husband that he is human, and that he is not a bear. But if what Mary said at the court is true, then the direct interpretation implies that she had inconsistent beliefs. She believed a singular proposition as well as its negation. Intuitively, however, there was nothing inconsistent about her state of belief when she saw a dark creature approaching in the woods and thought it was a bear.
This problem generalises. Assuming our attitude reports are by and large correct, the direct interpretation implies that people are belief-related to singular propositions about all kinds of things. How do these beliefs rationally interact? How do they respond to evidence? How do they guide behaviour? It's really hard to spell out a satisfactory answer.
Second, let's have a closer look at what Mary knew and didn't know about her partner. Even in long-term relationships, couples often have mistaken beliefs about one another. Perhaps Mary mistakenly believed that Mark was attracted to her sister. [Imagine we go on like this for a while.] But she did not mistakenly believe that he was a God, or a beetle, or a bear. – See? Now I said the opposite of what Mary said at the trial. I said she did not believe he was a bear. The truth-value of "Mary thought her husband was a bear" (on its de re reading) seems to depend on the context of attribution.
Friends of the direct interpretation might infer that what Mary Harshbarger believed at 7:55 pm on September 14 2006 is relative to a context of attribution. That is highly counter-intuitive. Alternatively, they might say that one of the two judgements is mistaken. But which one? And why?
Unlike the first problem, this one is really a linguistic puzzle. We are prepared to affirm and deny the very same belief report, depending on the linguistic context, without gaining or losing relevant information in the switch. One would like to understand what is going on here, and the direct interpretation of the report does not seem to offer an explanation. We are going to meet a lot of other linguistic puzzles later on.
For now, what I said should suffice to motivate considering an alternative to the direct interpretation.
On this view, ordinary people are not belief-related to singular propositions involving ordinary objects at all. The beliefs we have about objects in our environment always represent the objects under a particular "mode of presentation". This is a form of descriptivism, but it is not a claim about the meaning of proper names or other linguistic expressions. I will call it doxastic descriptivism.
According to doxastic descriptivism, what Mary Harshbarger really believed at the fateful moment was something like this: that creature approaching through the woods is a bear. She also believed: the person to whom I am married is not a bear. The two beliefs are obviously consistent.
One problem for doxastic descriptivism is that it does not seem to fit the way we talk. If people don't have singular beliefs about ordinary objects, how should we interpret de re reports that appear to attribute just such beliefs?
Here's how Hawthorne and Manley (2014: 52) put the problem:
Those who reject [the direct interpretation] need an alternative account of how the truth-conditions for [de re] belief reports are compositionally generated. Are we to deny that 'believes' expresses the relation believing, or are we to deny that 'Bill is happy' expresses a singular content? Pending some worked-out semantics of belief ascriptions or some novel criterion for when sentences express singular propositions, [the direct interpretation] is an attractive principle.
Return to "Mary thought her husband was a bear". On the Quine-Kaplan model, what makes this true (on its de re reading) is that (1) Mary thought that the creature approaching through the woods was a bear, and (2) in fact, the creature approaching through the woods was her husband. More generally, "S believes that x is F" is true iff there is a suitable role R such that (1) S believes that whatever plays R is F, and (2) in fact, x plays R.
The challenge is to explain how these truth-conditions come about. It is clear that the relevant role is not part of the meaning of the corresponding singular term. In English, "my husband" does not mean the creature approaching through the woods.
If we assume that belief reports expresses an interesting relation between the subject and some kind of content expressed by the embedded sentence, it is really mysterious how the sentence could have the suggested truth-conditions.
It helps to think of belief reports on the model of modal constructions, with 'believes' functioning like a necessity operator. The Quine-Kaplan truth-conditions then fall out naturally from an attractive semantics for quantified modal logic.
The semantics I have in mind is a form of counterpart semantics – very roughly the kind of semantics outlined in Lewis's 1968 paper on counterpart theory. But we'll need to make some changes and fill in some details.