Dear Jay, more about natural kinds 
Jay Odenbaugh wrote a provocative reply to my last post on realism. I was going to leave a short reply in the comments, but it ran long.

Reply to Jay

As I understand Jay's reply, LIZ (lizard front ends) might be a legitimate kind. Yet Jay wants to resist accepting any artibrary set as a kind; he gives the example of the members of the set {Jay's nose, Michael Keaton, Eiffel Tower}. Call this would-be-kind jayskind. He suggests two criteria that might be used to bar such a monster.

(1) Non-circularity

jayskind is not a kind, because the feature that distinguishes members of the set is just that something be a member of the given set.

Yet the items in the things might also be described as things featured in Jay's example; so he adds:

(2) Mind-independence

jayskind is not a kind, because the fact that the members figure in an example is just the result of his deciding that they should.

I do not think mind-independence can be settled so easily. Frog food is a natural kind because it is picked out from the environment by frogs. Although it is a frog-dependent kind, it counts as a natural kind in biological study of frogs. Thorough-going naturalism allows for a scientific study of philosophers. Although jayskind isn't an especially important kind, it is only Jay-dependent in the way that frog food is frog-dependent. Now that he has given it as an example, he cannot change what counts as a member of that set just by thinking a different thought about it.

Jay and I began discussing these issues at the last PSA, and we had the good fortune of having Dick Boyd join the conversation; the frog food example is Boyd's. If I recall Boyd's position correctly, he avoids counting collections like jayskind as a natural by only counting something as a real kind if it appears in some actual enquiry. No one has done a sociological study of the Magnus-Odenbaugh correspondence, and no one will. So jayskind is not a real kind. This embraces the first horn of the dilemma that I posed a while back: Kinds that now appear in our science were not real ones prior to the science in which they appeared. This is at least somewhat odd.

(3) Intension

I thought up this further criterion, which is akin to non-circularity. In Jay's example, there are three things that are members of this would-be kind. Because the extension of the set is stipulated, further members of the kind are precluded. Yet scientific kinds are not like this. They are open ended. Although we think that there are eight (or nine) planets in our solar system, one natural moon orbiting Earth, and zero golden mountains, these numbers are contingent. Nothing about the categories themselves determines the numbers to be 8, 1, or 0.

We can bar monsters like jayskind by insisting that there be more to natural kinds than simply a stipulated extension. Natural kinds have intensions, too. This requires (contra Quine) that there be intensions, but that is not asking too much of our philosophy of language.

Alas, this criterion will probably not be enough for Jay. Although jayskind does not count as a natural kind, things featured in Jay's example still does; and the latter is extensionally equivalent to the former.

'Natural Kind' as a relation

A different way of understanding Boyd's suggestion is this: Being a natural kind is not a second-order property that obtains of a predicate. Rather it is a relation between a predicate and a specified enquiry. "Frog food is a natural kind" must be elliptical for something like "Frog food is a natural kind for biology."

Although we might say that jayskind is a natural kind for the micro-sociology of the Magnus-Odenbaugh correspondence, that seems less brazen than saying that it is a natural kind simpliciter. It is certainly not a natural kind for physics, ecology, pharmacy, gastronomy, or any other interesting area of enquiry.

This would also allow us to distinguish between categories that are natural kinds for some actual enquiry and ones that are natural kinds for some possible enquiry. We would just need quantifiers and predicates that distinguish on kind of enquiry from another. We can say that electron was a natural kind for particle physics even before electrons were discovered; it was the existence of physics that changed, rather than the existence of the kind electron.

How about it, Jay?

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Great scot, Holmes! That was meant for us. 
Here is a puzzle about the interpretation of ficition. As I have discussed elsewhere, I recently discovered an oddity in the Sherlock Holmes story The Adventure of the Dancing Men. Holmes inspects the scene of the crime and finds a spent shell casing in the flower bed. "I thought so," he says. "The revolver had an ejector, and here is the third cartridge."

Revolvers, unlike semi-automatic pistols, do not eject shell casings when they fire. The ejector is a manual mechanism that is used when the revolver is emptied and reloaded; an ejector makes emptying easier, but it is of course possible to empty a revolver that does not have an ejector. So why is there a shell casing in the flower bed, and why does Holmes say that the revolver's having an ejector made a whit of difference as to whether the gunman left a shell behind?

My interpretation of this passage is that Conan Doyle either did not understand how ejectors work or made a careless mistake. Call this the Authorial Blunder interpretation. The demerit of my interpretation is that it refuses to take the story seriously as a story. When we interpret fiction, we try to figure of what sort of world the story describes. My interpretation refuses to say what sort of worlds Holmes-worlds are, because it gives an explanation in terms of facts about the author rather than facts about Holmes.

If we try to interpret the story while explaining the puzzle of the cylinder in the flower bed, what are our options? Some authors say that the gunman crouched down in the flower bed after firing the fatal shot, emptied his pistol, and reloaded. Call these Reload interpretations. These require either that the gunman was obsessive compulsive (so that he felt the need to reload even though he had five bullets left in his gun) or that he was carrying a single-shot pistol (rather than a revolver, as Holmes suggests). Moreover, Reload interpretations do not explain why Holmes' mentioning the ejector is anything but a non sequitur. The relevant thing to have said would have been: "I thought so. The gunman reloaded."

Since the Holmes stories are presented as Doctor Watson's recounting the adventures of Sherlock Holmes, we could say that Watson misreported Holmes' utterance. Call this a False Watson interpretation. According to such an interpretation, there are many different Holmes-worlds in which Holmes says something a propos of finding the cartridge; in all of them, Watson misreports Holmes' utterance as the one given in the story. This maneuver seems too slick. First, it opens the way for Holmes-worlds in which Watson makes up all the details of the stories. Second, there is no interpretive payoff. The stories are no richer if we attach an explicit "or so Watson says" to every sentence in them. Third, we are left wondering why Watson misreported Holmes' utterance. If it was a blunder on Watson's part, then False Watson is just a variant of Authorial Blunder.

There is another option: Given that Holmes said what he said and that Holmes is clever, then the revolver's having an ejector must be relevant to the cartridge's being in the flower bed. This would all make sense if revolvers kicked out spent cartridges in Holmes-worlds, much in the way that rifles and semi-automatic pistols do in the actual world. Watson would not remark on such a fact, because it would be perfectly ordinary in his world. This interpretation solves the problem at hand without any of the problems that faced Reload and False Watson. Call this the Alternate Revolvers interpretation.*

I find this final interpretation wholly unappealing. I presume that Conan Doyle intended for Holmes-worlds to be like the actual world. He meant for there to be differences, like the existence of a brilliant detective at 221B Baker Street, but he did not intend far-reaching and subtle differences like this one. If revolvers are different in Holmes-worlds, it was due to a mistake by Conan Doyle.

As such, Alternate Revolvers must agree with Authorial Blunder that Conan Doyle goofed.** Conan Doyle's goof does not make the story incoherent, and so we can still ask what Holmes-worlds must be like. Alternate Revolvers does this, plowing ahead to consider revolvers and ejectors in Holmes-worlds. Thus, it continues to take the narrative seriously as a story. Authorial Blunder refuses to do so. It uses the goof as a reason to overlook this passage when thinking what Holmes-worlds must be like. Is my resistance to Alternate Revolvers just an instance of the Problem of Imaginative Resistance?

* The Alternate Revolvers interpretation might be weakened so as to describe some Holmes-worlds. Other interpretations, like the Reload interpretations, might be true in some other Holmes-worlds.

** One might use this as part of an argument for Authorial Blunder on grounds of parsimony. If we use Ockham's razor to shave off the revolver's ejector, however, we might just as well use it to shave off the whole discussion of Holmes-worlds. In the actual world, there are just words on a page.

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Dewey to me one more time 
Thanks to a kind invitation from Matt, I've been sitting in on a reading group here in San Diego. They had already read two-thirds of the way through Dewey's Logic when I joined them. Fortuitously, they had just reached chapters that speak to the question at issue between Matt and I in our discussion here.

In chapters XIII and XIV, Dewey distinguishes between generic and universal propositions. The former are about kinds and the latter are about categories.

Kinds, for Dewey, are aggregates of things that share certain qualities.

Categories, on the other hand, are kinds that we have picked out in the course of inquiry. Categories are the symbol with which we model the kind.

I do not think that Dewey would selectively privilege some aggregates as genuine kinds, because any arbitrary aggregate will share some properties. As he notes, "Everything in the world is like everything else in some respects, and is unlike anything else in other respects" [p. 268]. In terms of my previous example, LIZ and ARD are genuine kinds because there really are lizard back-ends and lizard fronts. Prior to my formulating them, they were not categories.

There are such an enormous number of kinds that we could not have symbols for all of them. We choose our categories in the course of inquiry to symbolize those kinds that we think are important.

So far this is like Kitcher's realism. Since the cartoon version of Dewey is a crude pragmatist anti-realist, however, one might worry that Dewey's view really can't be realism at all. This concern would be misplaced for two reasons:

First, for Dewey, our categories as free-floating concepts are responsible to the kinds they are meant to capture. As Dewey puts it: "Since existence is existence and facts about it are stubborn, ascertained facts serve to test the hypothesis employed" [p. 266].

Second, I am here interested only in the pluralist strand of Kitcher's realism. He and Dewey would disagree on the value of the analysis of truth as correspondence, but that alone does not make Dewey an anti-realist. (Especially since Philip is wrong about it.)

To move beyond the exegetical point: This string of posts has considered a maximally-promiscuous realism about kinds. While I only knew of one adherent to that position, I could abide by calling it Kitcher's realism. Now that I have a second, I need a general name for the view. I propose maximally pluralist realism, but I would appreciate something more euphonious. Any suggestions?

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Chance and credence 
In his paper at the SEP, Alan Hajek argued for this analogy: One's degree of belief in P being equal to the objective chance of P is like one's categorical belief that P being true. That is, a degree of belief getting the world right consists in it matching the objective chances.

This position requires that there be objective chances, he argued that there are, and I'll presume it for now.

A problem for his position arose in various forms during the question and answer period. Consider a fair coin.* The chance that it will come up heads is .5. I flip it, and it does in fact come up heads. Before flipping it, I have degree of belief .5 that it will come up heads on that flip. After flipping it, I can either change to degree of belief to 1 or continue with degree of belief .5. Neither option seems very good. The former has me believing the truth about the flip, but I no longer acknowledge the fact that the coin flip was a chancy event. The objective chance that the flip would come up heads is still .5, even after it did actually come up heads. The latter would leave me ignoring evidence about how events actually turn out, in favor of intermediate degrees of belief which are presumed to preserve information about how they might have gone.

It seems to me, however, that this is not especially a problem with Alan's account. Rather, it is an artifact of representing his account in terms of the usual probabilist framework. The framework treats agents' degrees of belief as probabilities assigned to propositions in first-order logic, with probabilistic judgments represented as intermediate degrees of belief. That is clearly inadequate in this case. I do believe that the chance that the coin would come up heads is one-half, and I also do believe that it did come up heads.

There is a difference between a degree of belief which is meant to correspond to an objective chance and a degree of belief that is merely an intermediate belief about a matter that does not admit of degrees.

There are formal ways of representing this difference, but notice that it will not help to consider belief to be a probability distribution over probability assignments. If I am less than certain that the coin is fair, then there will be a distribution around .5. If I am less than certain that the coin came up heads, then there will be a distribution close to 1. A bimodal distribution with peaks at .5 and 1 would not represent either situation.

We might instead introduce an operator Ch(P,p), meaning that the chance that P is p. After the coin toss, my degrees of belief are DoB(H)=1 and DoB(Ch(H,.5))=1. This handles the distinction, but it also means that the probabilist story about degree of belief is doing no work here. We might just as well represent my beliefs as H and Ch(H,.5).

Although we might try other expedients, representing degrees of belief as probabilities is de rigeur. Philosophers often do it presumptively nowadays, just as it was usual to write sentences in first-order logic in the 1960s. Why? Here are a few possible explanations:

1. The usual probabilist framework works for many purposes. There is no need to use a more complicated formalism if you don't need to.

2. Subjective Bayesians deny that there are any such things as objective chances, except insofar as they can be recovered from convergence in subjective degrees of belief. They have no incentive to try and represent beliefs about things that don't exist. (I am not sure whether the Subjective Bayesian should say that no one actually has beliefs in objective chances or just that beliefs in objective chances are wrong-headed.)

3. There is no clearly correct way to accommodate the distinction. This is a problem, because many probabilists say that probability just is the logic of confirmation. This imperialism requires that there is one specific formal system and that it captures the relevant structure. Once we admit that belief involves structures that cannot be readily represented in the usual probabilist idiom, then we must admit that there is more to the logic of science.

* If determinism makes you think that you can't attribute objective chances to coins, suppose instead that it is a radioactive atom and that the event is it decaying during a period equal to its half-life.

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Sentry duty and a three-word vocabulary 
There were many good talks at the SEP last week, and I am still mulling over some of them.

I'll mention Brian Skyrms' talk briefly, because I am still mulling it over but don't have anything deep to say about it.

Brian offered simple evolutionary models of animal signalling. As an example, he pointed to Dorothy Cheney and Robert Seyfarth's work on meerkat and monkey signaling; see especially their paper on meerkats [pdf]. Meerkats take turns standing sentry, and call out if they seeing anything worth mentioning. They have (roughly) a three word vocabulary: raptor, jackal, and snake.

I was curious about meerkats in contrast with his other examples, because the meerkat signaling system can't be wholly separated from their taking turns on sentry duty. Even if one behavior predated the other, each is more valuable when accompanied by the other. So it's too simple to treat selection for the signaling behavior in isolation.

Also: If we learned meerkat vocabulary, we could play roshambo with it:

-- 1... 2... 3... jackal!

-- My snake bites your jackal.

-- How about best two out of three?

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