Relativism vs. Expressivism:
the case of epistemic modals

John MacFarlane, UC Berkeley

July 1, 2011 @ Sydney

  1. Introduction

Epistemic contradiction

Epistemic Contradiction
p, but it is possible that not-p

Subjectivism

Subjectivism
It is possible that φ is true, as used at a context c, iff what is known by the agent of c does not exclude φ’s being true at c.

Fundamental problems with subjectivism

Wrong subject matter

When I say, ‘Bob might be in his office,’ I am talking about Bob and his office, not myself or the extent of my information. Suppose the building is on fire and everyone has been told to leave. I am afraid that Bob might still be in his office. I am not afraid that I don’t know he’s elsewhere. (Yablo 2011, 230–1)

Agreement/disagreement

A: It’s possible that the letter will arrive tomorrow.

B: No, it’s not possible. They told me yesterday that they hadn’t even mailed it yet.

Agreement/disagreement

A: It’s possible that the letter will arrive tomorrow.

B: #I agree, but it can’t arrive tomorrow; they told me yesterday that they hadn’t even mailed it yet.

Huw Price on “probably”

If I disagree with your claim that it is probably going to snow, I am not disagreeing that given your evidence it is likely that this is so; but indicating what follows from my evidence. Indeed, I might agree that it is probably going to snow and yet think it false that this follows from your evidence. (Price 1983, 403)

Does it help to interpret the modal relative to all the evidence that is available in principle?

…consider the surgeon who says, ‘Your operation has probably been successful. We could find out for sure, but since the tests are painful and expensive, it is best to avoid them.’ The accessibility, in principle, of evidence which would override that on which the [single-case probability] judgment is based, is here explicitly acknowledged. (Price 1983, 405)

Retraction

A: It’s possible that the letter will arrive tomorrow.

B: No, it’s not possible. They told me yesterday that they hadn’t even mailed it yet.

A: Ah, then I stand corrected/I take that back.

Alternatives to subjectivism

Expressivism

It is possible that p is not used to make assertions, but to express an attitude of leaving-it-open-that p. The phrase that it is possible that p does not express an assertible content; possible modifies force, not content.

Relativism

It is possible that p expresses a possible content of judgment and assertion, but the truth of this content is relative not just to a possible state of the world but to an information state. The correctness of an assertion with this content varies with the context of assessment, and depends on the information of the assesser, not that of the speaker.

  1. Expressivism

The basic expressivist thought

Subject matter

It’s possible that Bob is in his office expresses an attitude towards the proposition that Bob is in his office, which is the real subject matter.

Agreement and disagreement

A: It’s possible that the letter will arrive tomorrow.

B: No, it’s not possible. They told me yesterday that they hadn’t even mailed it yet.

Retraction

A: It’s possible that the letter will arrive tomorrow.

B: No, it’s not possible. They told me yesterday that they hadn’t even mailed it yet.

A: Ah, then I stand corrected/I take that back.

The embedding problem

What to say about embedded uses, which do not modify force?

It is not possible that the letter will arrive tomorrow.

If it is possible that the letter will arrive tomorrow, then we should leave today.

If the letter was mailed on Tuesday, then it is possible that it will arrive tomorrow.

Joe thinks it is possible that the letter will arrive tomorrow.

There are at least two students who might fail the exam.

Hare’s gambit

Against Hare’s gambit

But it is possible that φ behaves differently than non-modalized sentences in conditionals, in ways that can’t be predicted from facts about their standalone behavior:

Against Hare’s gambit

But it is possible that φ behaves differently than non-modalized sentences in conditionals, in ways that can’t be predicted from facts about their standalone behavior:

Against Hare’s gambit

But it is possible that φ behaves differently than non-modalized sentences in conditionals, in ways that can’t be predicted from facts about their standalone behavior:

Upshot?

  1. We need a real compositional semantics to explain the interaction of epistemic modals with other expressions.
  2. The only way we know how to do this is by recursively assigning truth conditions.
  3. But assigning truth conditions to epistemic modal sentences is incompatible with expressivism.

But this is too quick.

  1. Relativism

Truth-conditional semantics

Indices

Compositional clauses

Contents

Postsemantics

Pragmatics

Constitutive norms governing assertion:

Norm governing belief:

Explaining epistemic contradiction

Modals in antecedents

Yalcin’s observation:

If p but I don’t know that p, then I’m deluded.

#If p but it is possible that not-p, then I’m deluded.

This cuts against ordinary subjectivism, but not the relativist view, which predicts the difference.

There is no nonempty set of worlds at which

p but it is possible that not-p

is accepted, so the second conditional crashes.

Modus tollens

Predicted to be invalid:

If it is raining, then it is not possible that the streets are dry.
It is possible that the streets are dry.
So, it isn’t raining. (!)

Interaction with subjunctives

#It’s not possible that the gun was his. But if we hadn’t checked the state records, it would have been possible that the gun was his.

This semantics allows us to shift the world independently of the information state.

Subject matter

The content expressed by

It is possible that Bob is in his office

is not about the subject or any particular body of information; it is “informationally neutral,” in the sense that its truth varies with the information state.

Moreover, the correctness of an assertion of this content does not hang on any particular information state; it, too, is relative.

Agreement and disagreement

A: It’s possible that the letter will arrive tomorrow.

B: No, it’s not possible. They told me yesterday that they hadn’t even mailed it yet.

According to subjectivism, B should agree that what A said is true. Relativism does not make this prediction.

Retraction

A: It’s possible that the letter will arrive tomorrow.

B: No, it’s not possible. They told me yesterday that they hadn’t even mailed it yet.

A: Ah, then I stand corrected/I take that back.

Retraction is called for by the norm governing retraction.

Upshot

The relativist view retains what is appealing about subjectivism while avoiding its problems. And it solves the compositionality problem where expressivism cannot.

  1. Expressivism revived

Gibbard’s “normative logic”

Yalcin’s nonfactualism about epistemic modals

These features are all shared with the relativist view.

Truth

Yalcin denies that questions of truth arise for epistemic possibility claims (e.g. 326).

Questions of truth

Care is needed here. It’s part of ordinary talk to say:

It’s true that it might be raining.

He said it might be raining, and what he said is true.

Our semantics should explain this. The expressivist can coopt the relativist semantics for monadic “true,” which gives it disquotational properties.

In what sense, then, do questions of truth not arise?

Belief contents

Yalcin denies that these information-relative semantic values correspond to a distinctive class of belief contents.

One might think of this as an ‘adverbialist’ model of epistemic possibility belief. Such beliefs do not correspond to a distinctive class of believed contents; rather, they correspond to a distinctive way of being doxastically related to a proposition. (309)

In the simplest version: “it might be raining” expresses the absence of belief that it is not raining; believing that it might be raining just is not-believing that it is not raining. In the more sophisticated version:

To believe that a proposition is possible, or might be, is for the proposition to be compatible with one’s view, and moreover for it to be an answer to a question one is sensitive to. (319)

Beliefs and contents

The key difference

Qualitative case

Epistemic akrasia?

Yalcin’s view makes a certain kind of epistemic akrasia impossible:

In the same way, Gibbard’s view makes a certain kind of normative akrasia impossible:

The choice between expressivism and relativism hangs on whether you think this is a bug or a feature.

A related difference

Yalcin’s view implies that any creature with the conceptual resources to entertain the question whether p and believe that p is also capable of believing that it is possible that p.

Fido believes that I might give him a bone.

On the relativist view, extra conceptual resources are needed, beyond what is needed to believe that p, to believe that it is possible that p.

Again: bug or feature?