Thursday, January 25, 2007

More On Incoherent Credences

Here's a thought which might help with the generalization point (see the end of my last post).

Suppose the case is as before except your credence in (p iff q) is 0.9 rather than 1. Then you aren't sure that your evidence concerning p is to be treated as evidence concerning q and vice versa, but you should think your evidence concerning p serves decently well as evidence concerning q and vice versa. Your credence in these two propositions therefore should not be able to get *too* far apart, else it will look like one of them (at least) is being influenced by something other than your evidence. Weakening your credence in (p iff q) correspondingly increases how far apart your credences in p and q can get before it starts to look like some untoward influence is at work.

Another point (thanks to Daniel for this): the reasoning I'm using here and in the original case involves an assumption that variation in credences without variation in evidence suggests that one's credences are sensitive to something other than evidence. One way of denying this would be to claim that evidence (sometimes) makes a range of different credences in p admissible but does not single out one in particular as correct.

It is not surprising that those who hold this permissive type of view find it harder than others to account for the strangeness of having two different credences in (what you know to be) materially equivalent propositions. They'll presumably even find it harder to account for the strangeness of having two difference credences in (what you know to be) one and the same proposition. Maybe permissive people should doubt whether there is anything epistemically wrong with incoherent credences. That wouldn't, I think, undermine my explanation of what sort of account people who think there is something wrong with it should give of that wrongness.

What's Wrong With 'Incoherent' Credences?

Define 'incoherent' credences as ones that don't satisfy the probability axioms. There are familar 'Dutch Book' arguments about what's wrong with having incoherent credences. At a reading group meeting today lead by Al Hajek, I became even more convinced than previously that they leave a lot to be desired (at least as they stand). I thought I'd have a shot at something else.

Ideally, it would be nice to formulate a norm of credence which incoherent credences - or rather, credences which you *know* to be incoherent (there needn't be anything irrational about credences which are *in fact* incoherent if you've no reason to think they are) - are in tension with. I thought of this:

NC: You should try to make your credence in p sensitive only to your evidence concerning p.

Now, suppose you notice that you have different credences in p and q and you have credence 1 in (p iff q). Your certainty that (p iff q) will (at least in lots of standard situations) enable you to (properly) treat all your evidence concerning p as evidence concerning q and vice versa. So that you have the same evidence for and against each of them. This means, since your credences in p and q are different, that at least one of those credences must be sensitive to something other than your evidence concerning the relevant proposition. You can see that you have violated a norm of credence.

This seems to me to be a decent explanation of what is wrong with incoherent credences in this sort of case. Is this kind of explanation sufficiently generalizable? I don't know yet. For one thing, I'm not sure how to get this sort of explanation going in situations where you don't have credence 1 in something. But then, I'm also not sure whether you can get clear cases of irrationality in situations where you don't have credence 1 in something. (In the above case, if your credence in (p iff q) wasn't 1, it would be less clear that it was an epistemic mistake to have different credences in p and q.)

Friday, January 19, 2007

Constitutive Independence

In my paper Realism and Independence I distinguished between modal independence and essential independence.

Modal independence of p from q:
There is a possible world where (p and not q)

Essential independence of p from q:
It's no part of what it is for p to be the case that q be the case

I argued that essential independence from the mental (not modal independence from the mental) is characteristic of mind-independence realism.

But there are other notions of independence in the vicinity as well. For one thing, 'what it is' talk might be interpreted the way I had in mind, as essence talk, or it might be interpreted as more like constitution talk. A third putative notion of independence is

Constitutive independence of p from q:
p's being the case is not constituted by q's being the case.

One reason I don't like the idea of using constitutive independence to characterize realism is that it seems to restrict the range of positions that can be classified as realist. One thing I like about essential independence as defined is that it is supposed to be metaphysically neutral on issues like whether facts or states of affairs exist. (It only talks about 'things being the case', which is intended as lightweight talk that could, but need not, be cashed out in terms of the obtaining of facts or states of affairs.)

By contrast, talk of constitutive independence seems on the face of it not to make sense unless we acknowledge the existence facts or something similar. If we have such things in our ontology, we can perhaps make sense of a constitution relation holding between them, analogous to that which holds between objects (or between objects and stuff).

Are there other ways to make sense of constitutive independence?

Tuesday, January 16, 2007


Apparently 'Jacques Derrida (deceased)' is among the 'Regular Visiting Faculty' at Stony Brook (scroll right down). Does he haunt them, or what?

What a terrifying thought.

Friday, January 12, 2007

Wittgenstein's Tenure Case

I've been following the interesting discussion between Jason Stanley and Aidan McGlynn on the "Wittgenstein Fallacy". I think both sides of this debate get it half right. There *is* something wrong with the current climate, because there *is* a chance that Wittgenstein would have got tenure under it.

Saturday, January 06, 2007

Chalmers on Ontological Realism

Today I have been mostly reading Dave Chalmers on Ontological Anti-Realism. (NB: Dave's paper is a draft, not a finished product. Still, since it's in the public domain, I thought it might be helpful to make a comment here since I think the point is important.)

A couple of quibbles then the biggie.

Quibble 1: I think it's inviting trouble to describe anything as 'the' basic question of metaontology, ethics, or metaethics (p. 1). Other basic questions of metaethics, for instance, besides Dave's ('Are there objective answers to the basic questions of ethics?') will plausibly include: 'What is the best methodology for ethics?' and/or 'How - if at all - do we know ethical truths?'. And many people might think that the basic questions of ethics, besides 'What is right?', include 'What is good?', 'What ought I to do?' and/or 'What is the force of ethical reasons for action?'.

Quibble 2: Those who hold that 'commonsense' and 'correct' ontology coincide in cognitive significance aren't thereby forced to be deflationary about correct ontology (p. 9). They might instead be inflationary about commonsense ontology, holding that it has the cognitive significance of - and is sensitive to the commitments of - correct ontology. (Or at least, I don't see why this option is off the table.)

The big one: Dave's 'ontological realism' (section 5) consists in attributing the following properties to all ontological existence assertions:
1. objectivity, which amounts to lack of sensitivity (regarding content or truth-value) to context (speaker's or evaluator's),
and 2: determinacy (having truth-value true or false).
His 'anti-realism' is defined as the denial of realism in this sense.

My worry about this is that 'objectivity' as Dave defines it is orthogonal to the question of mind-independence, which I suspect is what most of those who take themselves to be ontological realists because they think ontological claims are 'objective' will be thinking of. By Dave's lights, one can count as a realist about ontology despite thinking that There are Fs is true iff (and in virtue of the truth of) Someone believes at some time that there are Fs. But I think this position is pretty clearly anti-realist in at least one good (and commonplace) sense.

Moreover, I'm not sure that I know of a good (and/or commonplace) usage of 'realism' which goes along with determinacy of truth-value and lack of sensivity to context. No-one would say we are in danger of counting as anti-realists about physical space, say, just because we believe spatial language is full of indexicals and therefore not all spatial assertions are 'objective' in Dave's sense.

Update: I have cross-posted this to TAR where it has received some discussion from Chalmers.

Friday, January 05, 2007

Epistemic 'Ought' Does Not Imply 'Can'

Happy New Year everyone!

Yesterday Michael Smith visited ANU and gave a fun paper called 'Two Kinds of Consequentialism'. Afterwards the pub conversation turned to whether epistemic 'ought' implies 'can'. My hunch is that many different things may be expressed by epistemic uses of 'ought' in different contexts, and (more familiarly) the same kind of thing goes for 'can'. And it might be that for each epistemic 'ought' there's a corresponding 'can' which it implies. Nonetheless, I suspect that all or most (or at least most of the common) uses of the epistemic 'ought' express things which don't imply the things usually expressed by 'can'.

There's a recipe for creating counterexamples to 'ought' implies 'can' in the epistemic case which helps convince me of this. Take your favourite case of someone holding an irrational belief that she epistemically ought not to hold. (E.g. Carrie's believing at 5.40pm that aliens are invading the Earth despite there being absolutely no evidence to that effect.) Then make it so that the subject's holding that belief is beyond her control in your favourite sense. (E.g. Specify that Daniel has attached a brain-manipulating device to Carrie's head so that when he presses his remote control button at 5.40pm she will start believing that aliens are invading the Earth, despite having absolutely no evidence to that effect.) These will be cases where the subject epistemically ought to refrain from believing the proposition in question yet it's not the case that she can refrain from believing it.
It seems to be possible to follow this recipe for various different kinds of epistemic 'ought' (corresponding to various notions of epistemic irrationality) and various kinds of everyday 'can's (corresponding to various notions of control). It doesn't work for the weak 'can' of bare metaphysical possibility, of course, but 'ought'-implies-'can' isn't very interesting unless the 'can' is at least a bit stronger than that.