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Tuesday, January 29, 2008

MacFarlane, Kratzer-Conditionals and Knowing What You Ought to Do

At the AOC conference John MacFarlane gave a paper (co-authored with Niko Kolodny), defending an assessment-sensitive semantics for 'ought'. In MacFarlane-style assessment-sensitive semantics the truth-value of utterances will depend on features determined by the context of assessment and not just on features determined by the context of utterance and circumstance-shifting operators. Thus, my utterance of 'John ought to pay his bill' may have different truth-values, depending on who is considering it for truth.

The paper is very rich. I can't cover all the details. But the paper includes, as part of its defense, a Kratzer-inspired theory of indicative conditionals. On the theory in question, conditional 'ought'-statements are always narrow-scope rather than wide-scope. So, the conditional 'if I get drinks in the bar, then I ought to pay' has the correct form with the 'ought' taking narrow scope. 'It ought to be the case that if I get drinks in the bar, I pay', on the other hand, must be paraphrased as 'if I get drinks in the bar, I ought to pay'.

I have one concern about this account of conditional 'oughts', which piggybacks on John Broome's concern about narrow-scope conditional requirements. Consider the conditional 'ought' statement:

(1) If I (sincerely) assert the sentence 'there is a department meeting this afternoon', then I ought to believe that there is a department meeting this afternoon.

(1) seems true. After all, there is supposed to be a close connection between assertion and belief. But now consider the following scenario.

Scenario:
I have strong evidence that there is no department meeting this afternoon but I assert 'there is a department meeting this afternoon'.

Since I asserted that there is a department meeting this afternoon, it would seem that I ought to believe that there is a department meeting this afternoon. And since I have strong evidence that there is no department meeting this afternoon, it ought to be the case that I don't believe that there is a department meeting this afternoon. So, it ought to be the case that I believe and don't believe that there is a department meeting this afternoon. But this can't be right. So, something must have gone wrong.

MacFarlane rejects modus ponens. So, the following inference form is not unrestrictedly valid:

If I assert 'there is a department meeting this afternoon', then I ought to believe that there is one.
I assert 'there is a department meeting this afternoon
So I ought to believe that there is one

So he can avoid the unfortunate consequence. But there is an alternative move available. Broome's move. Broome allows for wide-scope 'ought' statements (or 'requirement' statements but I am here focusing on 'ought' statements). So, it is not quite right that if I assert 'there is a department meeting', then I ought to believe that there is one. Rather, it ought to be the case that if I assert 'there is a department meeting', then I believe that there is one. Moreover, detachment fails. So the following inference is invalid:

It ought to be the case that if I assert 'there is a department meeting', then I believe that there is one
I assert 'there is a department meeting'
Hence, I ought to believe that there is one

Of course, Broome could allow the following inferences:

It ought to be the case that if I assert 'there is a department meeting', then I believe that there is one
I ought to assert 'there is a department meeting'
Hence, I ought to believe that there is one

It ought to be the that if I assert 'there is a department meeting', then I believe that there is one
I assert 'there is a department meeting', and it is not the case that I ought not to assert 'there is a department meeting'
Hence, I ought to believe that there is one

My main concern with the MacFarlane move (i.e., his theory of conditionals) is that on the assumption that the first sentence is a narrow-scope 'ought' statement, the following instance of modus ponens seems exceedingly plausible:

If I assert 'there is a department meeting this afternoon', then I ought to believe that there is one.
I assert 'there is a department meeting this afternoon'
So I ought to believe that there is one

However, as we have seen, if we accept just this one instance of modus ponens, then we can derive a contradiction in the envisaged circumstances.

Here is a second potential worry about MacFarlane's (and Kolodny's) account. For MacFarlane, possible world-states are states compatible with what is known (by the assessor). The ideal world-states are a subset of the possible world-states (the set of the most ideal states). Now, consider 4-year old Mary. Her mom has told her that if her pants are on fire, she ought to pour water on them. She truly believes but doesn't *know* that if her pants are on fire, she ought to pour water on them, and she doesn't know that liquid hydrogen is distinct from water. So, in some of the possible world-states (where Mary is the assessor), water = liquid hydrogen and in others water is not identical to liquid hydrogen (since she doesn't know about the identity). Moreover, since she doesn't know that if her pants are on fire she ought to pour water on them, water = liquid hydrogen in some of the ideal possible world-states, and in some of those states, Mary's pants are on fire and she pours liquid hydrogen on her pants (causing an explosion). Assuming 'she ought to' and 'she is permitted to' are duals, it follows that if Mary's pants are on fire, she is permitted to pour liquid hydrogen on her pants, which seems unintuitive (even when she is the assessor).

For further discussion of MacFarlane's paper, click here and here.

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