Review of LaPorte's NKCC

Biology and Philosophy (2005) 20:859–868 DOI 10.1007/s10539-004-0835-5

Ó Springer 2005

Book review -1

Conceptual stability and the meaning of natural kind terms DAVID BRADDON-MITCHELL The University of Sydney Department of Philosophy Main Quad A 14 2006 Sydney NSW Australia E-mail: [email protected]

An essay-review of Joseph Laporte Natural kinds and Conceptual Change Cambridge Studies in the Philosophy of Biology, CUP 2004 Here’s the mix that LaPorte would have us believe: meaning change is pervasive in the history of science, but this is a harmless phenomenon. Natural kind terms typically change their meaning when scientific discoveries are made. But this does not lead to any post-Kuhnian relativism, because we can distinguish between theory change and meaning change. It is – according to LaPorte – theory change that makes our old terms useless, and thus encourages us to define new terms. For empirical discoveries often show that we should be eliminativists about the old terms, or else show us that the old terms are vague. Since terms that do not refer are pretty pointless, and so are ones that are hopelessly vague, the meanings of the terms shift so that they do refer, or are not vague. Thus there is no dangerous incommensurability, because we just need to be explicit about which language we are using – the old or the new. So we rarely discover the essences of things, rather discoveries prompt us to re-define terms so that newly discovered features of the world are essential. All of this requires that some parts of a theory are analytic, and LaPorte takes it that the way the causal theory of reference explains our responses to empirical discoveries about natural kinds show us that there must be analyticities: for only if there were would we be driven to eliminate an old term. This picture is something that I take to be true some of the time. But we should be less sure of the pervasiveness of the meaning change that is supposed to characterize the history of science. If it is not pervasive, and meaning change is something that sometimes occurs and sometimes does not in the face of surprising discoveries about natural kinds, then we need some principles that would distinguish these cases. LaPorte does not offer such principles, so eventually I will sketch an outline of what they might be. We should also be a lot less sure of the novelty of LaPorte’s claims about the relationship between the casual theory of reference and analyticity, of which more later. These claims are both better developed elsewhere, and are more contested than LaPorte allows.

860 I will deal first with an example of LaPorte’s that is supposed to be an example of stipulative meaning change in the light of evidence that, as previously understood, a term fails to refer. I will suggest that we cannot rule our the possibility that the changes are not stipulative meaning changes, but are rather revisions of our opinions about the intension of a term in the light of a scientific discovery plus some broadly analytic truths of a sort that LaPorte himself ends up being committed to. Here’s an example of LaPorte’s.1 Suppose it is true that we now take guinea pigs not to be rodents, despite their morphological similarity to them.2 This is because of the alleged discovery that there is no common ancestor of all and only the guinea pigs, mice and rats. In fact the closest common ancestor of these three groups is a common ancestor of horses and primates. What some taxonomists have in fact done is to narrow the extension of ‘rodent’ to exclude guinea pigs and their close relatives. So it looks like someone who once thought, before this discovery, that ‘guinea pigs are rodents’ was in fact wrong. But LaPorte thinks this is a mistake: in fact ‘rodent’ has had a stipulative meaning change. The empirical discovery tells us that as previously used, the extension of ‘rodent’ was empty. The discovery was that there were no rodents, as the term was then used. So there was a need to re-define, and there was no most natural re-definition. This is because the choice of narrowing the extension of ‘rodent’ was not forced on us: we could have equally broadened the extension of ‘rodent’ to include (inter alia) humans, or we could have declared ‘rodent’ to be a non-natural kind (or a natural but non-taxonomic kind) – as we have done in the case of analogous discoveries about ‘reptile’. Maybe this is so. But I see no reason to think it is true in general, and am not especially convinced in this case. How does LaPorte’s argument work? He seems to have re-invented unawares causal descriptivism.3 This is a view that endorses as analytic certain clusters of descriptions, including descriptions which ground meaning in hidden features of exemplars with which language users are causally acquainted.Some such simple theory for ‘rodent’ might have gone something like R1 ‘Rodent’ is a term for the natural taxonomic kind, if any, of which guinea pigs, rats and mice are members. If this had captured the general use of ‘rodent,’ then the discovery that there is no such group (a complex discovery which would need both an empirical component and a theoretical component: the latter being that cladistics gives the right account of natural taxonomic groups) means that, as it is used, it 1

LaPorte (2004) pp. 66 ff. LaPorte cites D’Erchia et al. (1996) in support of this view, while admitting in a footnote it is controversial, citing Phillipe (1997). It is more than controversial. Sullivan and Swofford (1997) provide compelling reasons based on mDNA evidence why it is not true. Of course it is, as LaPorte says, only an example. But surely the point of detailed real-life examples rather than thought experiments is that there is an attempt to get things right. 3 Classic presentations of the elements of this view include McKinsey (1978), Lewis (1984), Loar (1976), Kroon (1987), Jackson (1998a, b) and David (2002a, b). 2

861 would have been right to say that there were no rodents. This then leads to some meaning change: and since we are engaged in re-definition from scratch, then any such re-definition is allowed semantically. Pragmatics will allow us to choose any scientifically perspicuous change, such as that which includes the humans as rodents. But once we allow analytic clusters of descriptions, it is surely implausible that they would be as thin as R1. Exactly how thick the cluster should be – and how we can tell – is something I will consider later. But for now consider the following: R2 ‘Rodent’ is the term for the actual natural taxonomic kind, if any, to which most of the gnawing mammals with no canine teeth and strong incisors and with which humans have been causally acquainted belong, and of which rats and mice are especially paradigm members. It is important to the concept that it be a natural group, and it should be as narrow a natural group as possible consistently with including paradigm members. But should it turn out that paradigm rats and mice that have been causally important in history are taxonomically unrelated, then ‘rodent’ picks out these paradigm creatures as a non-natural kind. If R2 were the right analytic story, then what happened in the case of ‘rodent’ would no longer look like an arbitrary choice. Something like R2 could be understood as an outline of the concept , taking into account differing ideas held by different individual speakers, and their pattern of deference to authority. It predicts that we will not include marsupial ‘mice’ in our list of paradigms, because these are not the organisms with which we were in causal contact during most of the history of the term. It predicts that we would restrict ‘rodent’ rather than extend, because of the narrowness requirement, and it has a kind of indicative conditional structure: it tells you how the extension of the concept depends on various empirical matters, including whether there is any natural taxonomic kind that unites the gnawing mammals. Elsewhere I have argued that very often concepts have a structure like this, and that this structure can be, fallibly, inferred from the way beliefs about the extension of a term change over time,4especially in the light of empirical discovery.5 But of course it cannot be infallibly inferred. Oftentimes, no doubt, there is pure conceptual change, rather than change of apparent extension in the light of evidence, governed by an unchanged concept. Exactly what sort of evidence one might use to support one hypothesis over the other is going to be at the heart of a good theory of conceptual change, and I will touch on this question later in the light of my discussion of LaPorte on <jade>. It would be unfair, though, to give the impression that LaPorte thinks that his brand of causal descriptivism gives rise to concepts as simple as R1 above. In his discussions he frequently mentions a range of factors as well as the mere 4

It’s worth emphasizing that it is, on this view, only beliefs about the extension that change, for the extension is fixed by the concept and the facts. 5 Braddon-Mitchell (2005), Braddon-Mitchell (2003).

862 causal-descriptive formula. So – to stick with our example of but analyze it analogously with his discussion of <jade> <water> and <species> – he sometimes admits that there might be a number of different features that are analytic. Thus perhaps we might have the following: R3 (1) Rodents are the smallest grouping that contains rats, mice, and guinea pigs. (2) Rodents are a natural grouping. (3) Rodents are individuals with which we have been in contact. LaPorte’s take on cases like this is that when there are many features that are required, then discoveries are very likely to show that not all of the features are instantiated in anything. Thus we will face the choice of elimination or conceptual change – or, more precisely perhaps, elimination (of the category picked out by the unchanged concept) and conceptual change. The difference, then, between his view and mine is not the presence of many features in the cluster, but the presence of implicit conditional claims and weightings in the cluster. These weightings and conditionals tell you that not all features, or even any particular one feature, are conceptually required. The weightings and conditionals govern the extension when we find out what things in the world have which of the features in the cluster. There may also be conditionals in the cluster that tell you that some features are necessary if actual.6 Thus if, for example, there were a monophyletic group with a certain common ancestor at its head that contained all and only rats, mice, rabbits and guinea pigs, then having that ancestor would be a necessary feature to be a rodent. But if we find that the only monophyletic group that contains rats and mice but not humans and horses has a certain common ancestor at its head, then having that ancestor is necessary for being a rodent. For LaPorte, the problem with was that according to the old meaning we had to be eliminativists, and as this was unpalatable, there was conceptual change. But equally he thinks it is often the case not that there is no candidate referent given the old meaning, but that there are too many. The old concept may have an ‘open texture’, and there needs to be arbitrary conceptual revision to eliminate vagueness. Empirical discoveries can expose this vagueness and show that biological notions are underdetermined.7 It turns out that Brown Bears, Polar Bears, Black Bears and Giant Panda form a monophyletic group.8 But equally there is a monophyletic group which contains all of these as well the Raccoons Inkajous, Ringtails, Red Pandas, Coatis and their relatives,9 and yet another 6 An extended treatment of the two-dimensional idea that it can be analytic that a certain feature is necessary if actual but not otherwise can be found (using examples from the philosophy of mind) in Braddon-Mitchell (2003). See also Hawthorne (2002). 7 LaPorte (2004) pp. 84 ff. 8 O’Brien (1987). 9 According to some taxonomies: according to others there is no such group and the only monophyletic group which contains these contains also the whole of the arctoidea – including weasels, seals and dogs, See, e.g. the Berkeley Systematics pages at http://www.ucmp.berkeley.edu/ mammal/carnivora/carnivorasy.html

863 more restricted monophyletic group consisting of just the Brown, Polar and Black Bear. If the concept is limited by a causal-descriptive dubbing based on Black and Brown bears, how far should it extend? It must include Polar Bears, for they are included in the most restrictive natural group that includes the Black and Brown Bear. But should it include the Giant Panda? It would seem there is no fact of the matter. We could restrict ‘bear’ to the Black, Brown and Polar bear, and either treat the Giant Panda as an outlier group on its own, but a little closer to true bears than the Raccoons or Red Pandas, or we can take ‘bear’ to name the more inclusive monophyletic group. For LaPorte this is another example of the ubiquity of vagueness which leads to conceptual change: an arbitrary decision has to be made, which is not determined by the concept. Thus the original concept was vague, and since the elimination of vagueness from a concept changes it – no precisification of a concept is the same concept as the unprecisified one – so we have meaning change. Perhaps we do. If this is pure choice, or if it is driven by some agenda unrelated to the original concept, then it will be. But, again, can we be sure of this? The fact that cladism is taken to be a constraint on taxonomy does not tell us that all there is to taxon concepts is something like ‘the clade to which X belongs’. X will always belong to very many clades, and if we find that X belongs to a number of closely nested clades, the history of taxonomy tells us that we are inclined to group together X and its near relatives if they are morphologically similar enough. Pandas are morphologically a lot more like the other bears than are Raccoons, as well as being more closely related to the other bears than to Racoons. These two facts, as well as the fact that the paradigm bears and the Giant Panda form a clade, are perhaps jointly what explains the temptation to take ‘bear’ to refer to the members of that clade.10 It’s a temptation that might have been predicted in advance of the discovery of the Giant Panda and the Raccoon’s relatedness. It just tells us that there was more to the concept than the mere causal-descriptive dubbing. It does not help, though, just to be told that natural kind concepts contain something beyond causal-descriptive formulae. This is where there is a real lack in the book. We need some general story about what is included in natural kind concepts beyond the causal-descriptive formula. Let’s consider the picture that LaPorte paints for us in the final chapters. The causal theory of reference, he tells us,11 does not allow us to claim that there are discoveries of any kind unless there are analyticities. For only on the assumption that we have an account of the meaning of ‘water’ say, can a discovery count as the discovery that water is H20 (for example). Further, he tells us that there is an important difference between meaning change and theory change, contra the worst of the post-Kuhnian madness. Theory change and meaning change may both happen, but they can be distinguished: because very often it is theory change that leads to meaning change. Examples abound, including the ones we have already 10 11

And a few other organisms: there is much simplification in this discussion. LaPorte (2004) Ch. 6

864 rehearsed. When we do some empirical work our theory changes (without meaning change), and we discover that the extension of ‘bear’ is vague. This is intolerable, so we engage in some meaning change, and alter the meaning of ‘bear’ to remedy the situation. Similarly we discover that all life is related, so if a certain claim – that all organisms related by descent are members of the same species – was analytic (as it indeed seemed to some in the early 19th century12) there is only one species. This seems intolerable, so we alter the meaning of ‘species’. Once again, we get both theory change and meaning change, but they are distinct and separable. This all seems fine as far as it goes. The line of complaint I have pursued so far is that one can’t be sure that there is meaning change, rather than clarification of the explicit formulations of a concept. If some consequence seems intolerable, it might be because of factors that were part of the cluster of ideas that previously existed, and which were weighted more highly than the elements that were discarded. The other line of complaint is that these general claims: that the causal theory presupposes analyticity, that analyticity will give us an account of the difference between theory change and meaning change, and that it governs meaning change, are not new news. Nor are they uncontested news. Those who call themselves causal descriptivists have long maintained that the best way to make sense of the claims of the causal theory of reference is that there are causal descriptions buried in what might be a descriptive account, and that many of those descriptions will be implicit. The idea that analyticities are required to make sense of the discoveries characterized by the necessary a posteriori has most famously been articulated by, inter alia, Frank Jackson and Fred Kroon.13 But it is not all as easy as LaPorte would have us believe. There are challenges from Stalnaker14 and many others that complain that there is no analytic truth to be had, because causal descriptions are not rightly understood as part of the semantics of a term. Rather they are meta-semantics – they are a part of the general theory of the nature of reference, not of the meaning of particular terms. And even if we think that these and related complaints can be dealt with (and I do: but LaPorte seems unaware of them) developing an account of analyticity that selects from the descriptions held to be importantly true of a natural kind is still very problematic. For we need to choose from amongst the many descriptions that constitute the theory those which are analytic, and those which are merely synthetic. David Papineau,15 for example, advances a theory just on these lines – and the objection to that has always been that there is no obvious principled way to declare some descriptions, causal or otherwise, part of the analytic core, and others part of the periphery that’s part of the theory but not of the meaning. 12 13 14 15

LaPorte (2004) p. 148 Kroon (1985), Jackson (1994) Stalnaker (2003), Soames (2002) Papineau (1996)

865 As someone who thinks this can often be done, I do not complain that LaPorte requires it. But he does not give us any real acknowledgement of the difficulty of the task nor much by way of an account of how it is to be done. The only clue to how LaPorte thinks this can be done comes from his own accounts of the history of various notions. In these he occasionally cites passages where past theorists have more or less explicitly cited features as analytic. So for example in the mid 19th century William Hopkins16 tells us that it is part of what ‘species’ means that all organisms that are related by descent are members of the same species. But that by itself is no reason to count that description as analytic. There are various reasons for this. One is that it might just tell us that some individual is speaking an idiolect that they are trying to persuade others to speak. That one, or even a few, speakers or writers make a claim does not mean that the claim they make is right about the weighted average of usage over a community. So even if they speak truly of their own usage, that is not apodeictic evidence about the concept at the time. Another is that they may be in error about their own usage – we are not infallible about our own meanings, even if we have some kind of authority over them.17 Fallibility can come from a number of sources. One is that the various conflicting elements in a cluster of meaning can pull in different directions, and which is in fact the right one may depend on factors not explicitly known by the agent. So, for example, the agent may hold that it is taxonomic or scientific usefulness that settles potential clashes, and that claim may be analytic. But they may be mistaken about what is most taxonomically or explanatorily useful. A closely related error is that of confusing judgements about necessity with analyticity. These are subtle and essentially philosophical distinctions. So, for example, if it is held by Jones that ‘species’ names the principled grouping that underlies all the paradigms, and if courtesy of some non-Darwinian beliefs, Jones thinks that these principled groupings are all entirely non-overlapping lineages, then that important fact is likely to be taken as of the essence: rigidification happened before Kripke invented the term. But once it is taken to be of the essence, in explicit theorizing, it is likely to be, perhaps mistakenly, taken as analytic. Especially as a posteriori necessity is something only recently discovered explicitly, and even more recently understood. So there is a possibility of error on the part of past users about what was part of the meaning of the theoretical terms – and the theorized folk terms – that they used. In addition there is the question of whether the smallish number of writings bequeathed to us is a good guide to the structure of the concept at large. This seems to put us in a difficult epistemic position, and make a project like LaPorte’s difficult to the point of practical impossibility. The right answer to the question of whether there has been meaning change may always be ‘who 16

LaPorte (2004) p. 148, Hopkins (1973) Braddon-Mitchell (2004) gives an account of the sense in which agents do determine their meanings, consistently with their explicit articulations of them being fallible. 17

866 knows’. Real pessimists might think that there can be no semantic fact of the matter if it is that intractable, in which case the meaning change/theory change distinction comes back into doubt, and we are plunged back into post-Quinean, neo-Kuhnian skepticism. So finally I should say something about how to establish what is analytic about natural kind terms in common use. This is what we would have to do to establish, on a case by case basis, whether the possible accounts I have given of and are remotely plausible, or whether there has indeed been a change in meaning. There is a variety of evidence we need to work with. We need explicit pronouncements, we need past and present judgments on cases, we need the actual history of changes in these kinds of evidence, and we need historical information about what the influences were on these changes. All are crucial, and all will need to be deployed very carefully to test any of the assertions about meaning change or lack thereof that LaPorte makes. By way of example, consider a case where explicit pronouncements are contradicted by the progress of usage. LaPorte gives us a very nice example in the history of the use of jade’ in English, and of the cognate term in Mandarin.18 In both cases ‘jade’ ends up picking out a non-natural kind – green stones that can be easily carved and are of natural provenance. But, early in both histories, there are nice examples of people who are inclined to restrict the usage of ‘jade’ to jadeite: one of the two mineralogical kinds that make up most of what is now called ‘jade.’ There is a 1911 Encyclopaedia Britannica entry19 that says essentially that while the vulgar might use ‘jade’ to name a social-functional kind, strictly speaking it is just jadeite, and nephrite is fools’ jade. But by 1936 it’s becoming clear that ‘jade’ picks out a non-natural kind.20 LaPorte’s moral is that there has been meaning change: we have some testimony as to past meaning, and then that meaning shifts. We can see that theory change is about the nature of green minerals, and the meaning change issue is about what to call them. I think we can perhaps settle this issue, but it requires more information. We need to know why it became less defensible to claim that ‘jade’ referred only to jadeite. So let me propose an alternative story about ‘jade,’ and conclude with a discussion of how we would settle the issue. Suppose that ‘jade’ meant ‘The natural kind underlying the green carvable stones if there is one, otherwise the non-natural kind of green carvable stones.’ On this supposition about what was analytic about ‘jade’21 there has been no meaning change: only a recognition that there is no natural kind to rigidify on. Thus there has been a discovery that ‘jade’ refers to the non-natural kind – which on this supposition 18

LaPorte (2004) pp. 94–100. Rudler (1911) p. 122. 20 See e.g. Spenser (1936) p. 212 21 Aficionados of two dimensional semantics will notice that this meaning is an a-intension: ‘jade’ means the same thing in this sense of ‘means’ in worlds where it means something different in another sense of ‘means’ – the referential sense. 19

867 it always did, it’s just that people were unaware of this as they were empirically mistaken. Each hypothesis explains the facts. LaPorte’s explains it by saying that ‘jade’ has a simple, explicit, unconditional and unweighted meaning that changed. The alternative is that the meaning of ‘jade’ was more complex, tacit, and unchanged. We could support LaPorte by saying it is truer to reported claims about the meaning of ‘jade.’ We could support the alternative by saying it helps to explain the changes in beliefs about the extension of ‘jade.’ The second has to explain away the explicit evidence, but it can do so by saying that there is a near supposition of naturalness in the meaning of ‘jade’ – ‘jade’ is ideally a natural kind term. It is thus unsurprising that many will explicitly flirt with restricted reference to jadeite so as to secure this, until the importance of the non-natural kind that was always built into the concept reasserts itself. How do we choose? We need to know what influences are at work. Suppose that between the time of the first dictionary entry and the second, there is big cultural lack of confidence in the importance of natural kind terms in general. That would support the change of meaning hypothesis. Alternatively, imagine that the cultural importance of the artifactual kind ‘carvable green stone’ increased dramatically during the time: perhaps jadeite/nephrite becomes a culturally crucial marker of prestige, whereas before it was not. That too would help support the change hypothesis. Imagine further that there were two writers; one defending the view that ‘jade’ is nephrite, the other that is the disjunction. No-one seems to have any view on which is preferable. Due to a sudden inheritance and crucial bribery, the second writer is elected to he presidency of the Royal Society, and discredits all the writings of the first. Once again this would support a view that there was pre-existing vagueness or ambiguity, and that there is meaning change inasmuch as the vagueness is removed politically. Suppose further we find people saying ‘Hell there is no fact of the matter, but we have to do something, so let’s settle it the disjunctive way. Yet more evidence for the change hypothesis’. But if none of these are true, and the eventual explicit formulations of the meaning of ‘jade’ come to be disjunctive, and if this appears to reasonably resilient and non-flukey – be the result of some equilibrations between expert and non-expert users that tracks their semantic intuitions – then perhaps that is evidence for the lack of change of meaning view: the changed opinions about the reference of ‘jade’ are explained by an unchanged semantics interacting with a range of empirical discoveries. The idea is that we can sometimes explain the change of opinion about reference by hypotheses about what is implicitly analytic, and how these analyticities interact with empirical discovery. But equally, sometimes it really is the case that there is semantic change. Finding out which is which requires subtler history than LaPorte offers, for all its interest, and spelling out the semantics and meta-semantics will require tighter philosophy as well.

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