Just for fun I decided to actually read the edition of the AJP in which I have two entries, and see what fun things we can find. And there’s quite a bit, as we’ll see.

Jennifer McKitrick, A Case for Extrinsic Dispositions

I never understood why people say dispositions have to be intrinsic properties, and McKitrick apparently hasn’t either. But she’s actually done something about it. She starts with six examples of dispositions that look fairly extrinsic: the power to open a particular door, weight, the disposition to dissolve the contents of my pocket, vulnerability, visibility to humans, recognisability. (I’d been meaning to write something about vulnerability as an example of an extrinsic disposition. I was rather comprehensively beaten to the punch here.) Some of these look fairly artificial, though McKitrick does have arguments that even hackneyed examples of extrinsic dispositions should still be enough to refute the theory that all dispositions are extrinsic.

McKitrick considers several objections to the claim that these are examples of extrinsic dispositions. The strongest response is that although the properties are picked out relationally, they are in fact intrinsic properties. (For more on relational expressions that denote intrinsic properties, see my Stanford entry on intrinsic properties.) It’s very important to be aware of this distinction, but it doesn’t seem to be relevant here, at least in some cases.

What was most interesting to me about this wasn’t whether some dispositions are extrinsic, because I think McKitrick is obviously right, but what we can learn from considering tests for extrinsicness about the content of ordinary terms. So let’s assume that Earth, Moon and Travel are all people, and they are all, miraculously, intrinsic duplicates. Earth and Travel live on earth, and Moon on the moon. Earth and Moon are home right now, while Travel is currently holidaying on the moon. Which of the following three sentences seem to be true?

(1) Earth weighs more than Moon.
(2) Earth weighs more than Travel.
(3) Travel weighs more than Moon.

I think my intuitions here are inconsistent – (1) is true but neither (2) nor (3) is true. It’s consistent to say (1) is determinately true while neither (2) nor (3) is determinately true, and of course if you don’t assume ‘weighs’ is linear you can just say (1) is true and (2) and (3) are false. But it is hard to work out. I hoped that thinking about these cases would clarify a tricky question. If weight is extrinsic, which I think it is, what is it sensitive to? McKitrick assumes/stipulates, following Yablo, that it is sensitive to where you currently are. I think it’s more plausible that it’s sensitive to where you normally are. McKitrick’s version would have (2) true and (3) false, mine would have (3) true and (2) false. Intuition says, well I think intuition says it wants a holiday.

The vulnerability example really is very strong. If Athens and Olympus are intrinsic duplicates, but Athens is close to the sea and vulnerable to a sea-based attack, while Olympus is in the mountains and only reachable overland, then (4) is very plausible.

(4) Athens is more vulnerable than Olympus.

If Sparta has no plans to attack Olympus, and they have no weapons that can be transported overland to Olympus, and the gods favour Olympus and would instantly smite anyone who dares attack it, then I guess (4) is even more plausible.

There’s a really geeky reason, even by philosophical standards, for thinking that dispositions are extrinsic. One might think that a wine glass is fragile in virtue of the intrinsic structure of its chemical bonds or the like. There’s a McKitrick style argument for its fragility being extrinsic. Imagine a duplicate of it in rubber-walled room world, where literally all the surfaces are bouncy. Is that glass fragile? Maybe not! But there’s also a geeky reason. Consider a large part of the glass that consists of all of it minus a small chip off the base. I think this object (a) exists, (b) is not a glass and (c) is not fragile. I think it’s possible that the glass could be the only fragile thing on the table, so parts of the glass are not fragile. But a stand-alone duplicate of the glass, a glass as it were with a chip off the old base, is fragile. Conclusion: fragility is extrinsic.