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July 08, 2016


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"It is irrational to do something at the same time as believing that one objectively ought not to do it."

What about the Regan/Jackson/Parfit-style case? To illustrate, take Parfit's Mine Shafts case, where opening Gate 1 will save a 100 if they're in shaft A and save 0 if they're in shaft B, opening Gate 2 will save 0 if they're in shaft A and 100 if they're in shaft B, and opening Gate 3 will save 90 regardless of which shaft they're in. Now, suppose you believe (rightly) that you objectively ought not to open Gate 3. You objectively ought to open either Gate 1 or Gate 2. But it doesn't seem irrational to open Gate 3 while believing that you objectively ought not to open Gate 3.

Damn, Ralph, I was just working on something like this and I'm certain that anything good I come up with will be scooped by entries in this thread. One line that I was considering, which speaks to Doug's question, is just to adopt a view on which the objective-ought either (a) does not satisfy an akrasia constraint or (b) is not determined by what is objectively best (i.e., best given the total state of the universe). I think a perfectly natural line to take is (if you like the anti-akrasia constraint) just that the lesson of the Regan case is pretty much that the old-school assumptions about objective-ought are mistaken. Either there's no useful notion there at all (something like Zimmerman's line) or there's a notion there that isn't what Moore takes it to be.

Just to clarify the previous - Doug's worry can be met by simply denying that in the relevant 3 option cases it would be rational to believe there's any sense in which this subject ought to do what's objectively the best. [If we have the old-school view about objective and subjective ought, the subjective ought is something like the thing that is both (a) rationally believed to be the objective-ought thing to do and (b) thus rationally believed to be best in light of the total state of the universe. The subject knows she ought (in some sense) do the thing that couldn't be the thing that is best in light of the total state of the universe so, given the anti-Akrasia constraint, we get that the objective-ought thing to do, if there's such a thing, couldn't be the thing that could turn out to be the best given the total state of the universe.]


I think Doug is right about this. You say,

if this belief [viz., that she ought not to do A] is rational, then the proposition that doing A does not maximize the relevant value will have probability 1. It follows that doing A cannot maximize the expectation of this value according to this probability function, and so doing A cannot be rational.

But it doesn’t follow. In the kinds of cases Doug mentions, even though the probability that A maximizes the value is zero, A does maximize the expected value. This is a general feature of expectation, not a special feature of value. (There’s a philosopher named ‘Jacob Ross’ who has written about such cases in detail, and a philosopher named ‘Mark Schroeder’ who has a paper-in-progress about them – just on the off chance that you should run into one of them...)

Doug and Jamie --

You're completely right. The formulation that I posted yesterday contained a terrible mistake. I have now amended my formulation so that it removes the terrible mistake. (There's also a philosopher named 'Ralph Wedgwood' who has discussed these cases in detail, especially in "Akrasia and Uncertainty"....)

A great piece posted! thank s lot

This was a nice post.

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