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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Rumor Volat 
Tonight was the opening session of the Society for Exact Philosophy. Walking past Brian Skyrms, I said hi and congratulated him on his new position. He was somewhat taken aback, because he only just agreed to it-- not that it is secret, but there hasn't been a public announcement yet.

News travels fast these days.

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An angsty tableaux 
Yesterday was the last class meeting for my Existentialism course. During the discussion, one of the students drew a doodle in her notes. She showed it to me; with her permission, I've pasted it in below. It summarizes the course, more or less. The philosophers we studied are on the left. She and several of her fellow students are on the right. There I am in the upper corner.

Although I am depicted as being above Kierkegaard's God, this was only because she was running out of space. I don't think any sacrilege was intended.

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