The Reference of Natural Kind Terms

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Preface

This book is the result of my research on the subject of reference throughout the last years. I published a book on the reference of proper names in (2006) and after that publication I began to envisage the writing of a book on the reference of natural kind terms. Nevertheless, my research on other subjects and my duties in many academic tasks delayed the completion of the present book.

This book is devoted to the examination of various sorts of reference theories on natural kind terms, mainly causal and descriptivist, focusing on the reference of natural (chemical) kind terms, especially on the term “water”, one of the terms that has been at the center of the contemporary discussion on the reference of natural kind terms. Although H. Putnam’s and S. Kripke’s theories are at the core of this book, it also deals with the theories of some other authors criticized by them, as well as with some more recent versions of reference theories of natural kind terms. One of the claims of the book is that the antagonism between causal and descriptivist reference theories on such sorts of terms is not as great as is usually assumed.

In the last years the contributions on natural kinds and natural kind terms have increased exponentially and we have not intended to cover all of them. In the section of References there only appear the contributions that we have taken explicitly into account. Other interesting and important writings were not included there if it was estimated that they were not relevant enough for the guidelines or the content of this book. For instance, although important, we have not taken into consideration the homeostatic property cluster theory put forward by Richard Boyd, first mainly applied to terms for biological kinds and later extended to other natural kind terms, but which in our opinion is not so relevant for chemical kind terms – see however Magnus (2012) – or, at least, for the controversy between causal and descriptivist reference theories regarding these terms.

The content of several sections of this book, especially some preliminary versions, have been the subject of lectures, seminars and presentations held at different conferences and research centers in various countries, among them Argentina, Austria, Bulgaria, Chile, Colombia, Costa Rica, Croatia, France, Germany, Great Britain, Greece, Ireland, Italy, Mexico, The Netherlands, Poland, Portugal, Romania, Spain and Switzerland. I am grateful for the comments I received at those events. At the Complutense University of Madrid I have used parts of the book in my teaching of the subjects “Reference Theories” and “Philosophy of Language”, and the students’ commentaries have been highly useful. ← 9 | 10 →

There are some authors whom I should mention who have contributed to this book with their written comments, unpublished works or advice. I would like to first thank, now posthumously, Hilary Putnam, who read parts of chapter 5 and encouraged me to keep working on this project; he also sent me several of his relevant manuscripts and some by other authors one year before their publication in R.E. Auxier et al. (eds.) (2015). I am also grateful to Edouard Machery for sending me a yet unpublished article, indicated in the section of References as Machery, E, et al. (forthcoming), and to Frank Jackson for making available to me the manuscript indicated as Jackson, F. (2015). I also appreciate Genoveva Martí’s and Max Freund’s comments on section 4.2., and the former’s remarks on section 8.3. I thank Andrés Rivadulla for his suggestions on the Introduction. I am also grateful to Marisa Ferrari and Judith O’Hara for the English stylistic revision of the manuscript.

Parts of the content of this book have appeared, although generally in preliminary versions, in other publications, namely, “A comparison of the semantics of natural kind terms and artifactual terms”, published by Springer in 2016, “Reference fixing and descriptions”, by Peter Lang in 2016, “Kripke, Putnam and the description theory”, by Walter de Gruyter in 2014, “Kripke and Mill on natural kind terms” and “Has Locke’s semantic theory been refuted?”, both published by Ontos Verlag, in 2012 and 2010 respectively, and in my (2006) and (2016). I am grateful to the publishers for their consent to the reproduction of some of those writings’ fragments in the present book.

The publication of this book has been supported by the Spanish Ministry of Economy and Competitiveness in the framework of the research project FFI2014-52244-P.

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Introduction

The question of reference is one of the main problems of Philosophy; put in a general way, it is the question of how our words and thoughts get connected to the objects or entities about which we talk and think. By reference in the field of language, or linguistic reference, it is generically understood the relation between language and the world, that is, between our words or expressions and the objects and entities of the world. In this book I will only deal with linguistic reference, to which I will allude simply, as it is usually done, as reference.

The notion of reference conveys a (dyadic) relation holding between an expression and an entity or some entities; these entities which will be, as a rule, extra-linguistic, are the referent of the expression. Therefore, the relation of reference takes place between an expression and its referent. Nonetheless, it is relevant to make two qualifications. On the one hand, the term “reference” is very often used ambiguously, since it is frequently employed not to signify the relation between an expression and its referent, but instead of the expression “referent”. This ambiguous use of the term “reference” is exceedingly extended and I will not attempt to avoid it. Thus, I will frequently use the expression “reference” instead of “referent”, although the context will make it clear if by “reference” I mean a relation, the reference relation, or the entity or entities that constitute the referent of an expression. On the other hand, reference can be understood not as a dyadic relation, but as a triadic relation between speakers, or language users, a linguistic expression and the referent – or even as a relation with more arguments; e.g., a tetradic relation, the additional argument being the context, although I will leave aside this latter view (see section 8.5.). If reference is conceived as a triadic relation, to say that an expression refers is a simplified way of speaking; in the strict sense, it should be asserted that a speaker refers to an entity by (the use of) an expression or that an expression (as used by a speaker) refers to an entity. Some authors claim that when reference is conceived as a dyadic relation holding between an expression and its referent we are viewing reference as a semantic phenomenon, while according to the conception of reference as a triadic relation, this is a pragmatic one (see Abbott 2010: 2 f.). I will not put much emphasis on this distinction, since the claims about the reference of expressions could be paraphrased as assertions about the speakers’ use of them in order to refer. Thus, I will assume in general the view of reference as a dyadic relation.

Among the questions that can be posed concerning the reference of expressions, the most important one concerns the nature of the reference’s mechanism, ← 11 | 12 → i.e., by virtue of what expressions get connected (that is, refer) to certain entities or, as I will put it in the following, how the reference of expressions is determined. The answer to this question requires the formulation of a theory which explains the relation holding between expressions and their referents. The theories of reference are mainly answers to this question. Nevertheless, since a theory that explains the way in which the reference of expressions is determined will state the conditions to be fulfilled by their referents, our intuitions about which are the expressions’ referents will serve as a criterion of adequacy for the theories about how their reference is determined.

The two main types of contemporary theories on linguistic reference are the causal and the descriptivist theories. The former theories are also denominated causal-historical (see, e.g., Lycan 2008 and Reimer/Michaelson 2014) or historical-causal (see, e.g., Devitt 2006a), whilst the latter are also called description theories, but the terminology most often used at present for the latter, and the one I will employ is that of descriptivist theories– another label often used is “descriptivism”. However, the denomination “descriptivist theory” – as well as that of “description theory” and “descriptivism” – is ambiguous since there are such types of theories on the reference of expressions and on their meaning (see, e.g., Devitt/Sterelny 1999, Lycan 2008 and Reimer/Michaelson 2014). This is understandable because most of the advocates of descriptivist theories concerning the meaning also maintain such sorts of theories about the reference, claiming that the meaning of an expression determines its reference. Nonetheless, since it can be distinguished between the meaning and the reference of an expression, I will distinguish between the descriptivist theory of meaning and the descriptivist theory of reference, and I will use the simple label descriptivist theory when it is clear from the context if I understand by it one of its two versions, or to allude to that sort of theory in a general way whenever the distinction between its versions for the meaning and for the reference is not important or relevant. The dispute between these two sorts of reference theories, causal and descriptivist, mainly concerns the question of how the referent of our expressions or terms is determined. Put in a very general way, according to the descriptivist theory, the reference of a term, in its use by a speaker, is determined by properties or descriptions that the speaker associates with the term; in accordance with the causal theory the reference of a term is determined by causal (or historical) links between the uses of the term by speakers whose first link is the use of the term by the speaker who introduced it.

The debate between these two sorts of theories has concerned various types of linguistic expressions, although proper names and natural kind terms have been in ← 12 | 13 → the centre of that controversy. This book focuses on the reference of natural kind terms – regarding the reference of proper names see Fernández Moreno (2006).

Natural kind terms are the terms whose function is to refer to natural kinds or to the members or instances of such kinds. Natural kinds pose many different sorts of questions, the following being two of the main ones. Some of them are of a metaphysical nature, like what is the ontological status of natural kinds. The other central sort of questions is of a semantic character, such as what natural kind terms mean and how their reference is determined. In this book I will concentrate on the reference of natural kind terms, albeit most reference theories are linked to a meaning theory. Although both sorts of questions, the metaphysical concerning natural kinds and that regarding the reference of natural kind terms, are bound together, it can be convenient to distinguish them, because the answer to one of them does not necessarily settle the answer to the other.

However, it is to be recognized from the beginning that there is no precise and unanimously accepted characterization of natural kinds.1 There are mainly two sorts of proposals on this matter. One of them characterizes natural kinds by drawing some more or less intuitive distinctions between natural kinds and non-natural kinds, but without aiming to provide a definition of natural kind. Natural kinds are usually distinguished from arbitrary groups of objects such as what you have for lunch or the cats born on a Sunday. These are clear cases of non-natural kinds, whilst, as I will indicate below, among the paradigmatic natural kinds are natural substances, such as water and gold. Thus, it can be claimed that the distinction between non-natural kinds and natural kinds points to the “contrast between what is arbitrary (heterogeneous, gerrymandered) and what is not” (Koslicki 2008a: 201; see also Koslicki 2008b: 789). Notwithstanding, natural kinds should also be distinguished from other sorts of kinds, especially from artifactual kinds, for example, tables and pencils. Nonetheless, this distinction cannot be made coincident with the one between kinds whose members are found in nature and those whose members are man-made. Among the former are the kinds mud, dust and shrub which are hardly conceivable as natural kinds, whilst among the latter are the kinds technetium and diamond, which are plausibly regarded as natural kinds (see LaPorte 2004: 18). Thus, it can be conceded that the distinction between natural kinds and non-natural kinds “is not sharp, but rather one of degree, so that perhaps kinds can ultimately be classified into more or less natural ones along a spectrum of some sort, with clear cases on either side ← 13 | 14 → and a good bit of indeterminacy in the middle” (Koslicki 2008a: 203; see also Koslicki 2008b: 790, LaPorte 2004: 23 and some of the contributions in Sosa et al. 1985, including the ones by Moulines, who is critical of that distinction – see Sosa et al. 1985: 127 and 131).

Nevertheless, this type of considerations or similar ones should be supplemented with another sort of proposal to characterize natural kinds, that is, with a definition of natural kind. Although, as previously indicated, there is no precise and unanimously accepted characterization of the notion of natural kind,2 it is pertinent to mention some of the definitions of that notion that have been proposed.³ In the writings of some of the authors that have dealt with the semantics of natural kind terms one finds statements like the following: “Natural kinds are real causal powers that order the world in which we live […]. In general, natural kinds are the sorts of things that are naturally amenable to scientific investigation” (Carlson 1991: 370).

One of the authors whose semantic theory on natural kind terms has been at the centre of the contemporary discussion, H. Putnam, put forward in (1970a) the following characterization of natural kinds: “[C]lasses of things that we regard as of explanatory importance; classes whose normal distinguishing characteristics are ‘held together’ or even explained by deep-lying mechanisms” (Putnam 1970a: 139).

One of the definitions I favour, inspired by that proposed by Simonian (2005: 54), is the following: natural kinds are the kinds posited in a theory of natural science. This definition does not exclude the kinds, and hence the corresponding terms, introduced before their inclusion in a theory of natural science, on the condition that they would later come to be incorporated within the framework ← 14 | 15 → of such a theory, like the kinds water or gold; thus, the corresponding vernacular terms would be natural kind terms only in a derivative sense. This definition has a feature that, at least in my opinion, constitutes an advantage, namely, it enables that there be natural kinds without instances and therefore natural kind terms without reference or whose reference (extension) is the empty set, for example, the term “phlogiston”. However, that proposal should be made more precise, which would need to be supplemented with a characterization of natural science or at least with a criterion to distinguish natural sciences from other sorts of sciences, sometimes called “special sciences”, like meteorology, and furthermore from that group of special sciences that are the social sciences, like anthropology. Here the question comes up whether kinds from non-natural sciences can be considered as natural kinds. This question can also be posed by some features of Carlson’s and Putnam’s characterizations already mentioned, especially by Carlson’s claim that natural kinds are “real causal powers that order the world in which we live” or by Putnam’s assertion that natural kinds are “classes whose normal distinguishing characteristics are ‘held together’ or even explained by deep-lying mechanisms”. Although there is a rather common-sense understanding of such claims, which point to an intuitive notion of natural kind, only under some stipulations, which can be more or less arbitrary, resorting to them would enable kinds of non-natural sciences to be distinguished from natural kinds. Nevertheless, if this desideratum is not considered as acceptable one could modify the third mentioned definition of natural kind in the following way: natural kinds are the kinds posited in a theory of science.

It can be claimed that the third alluded definition of natural kind shares another feature with those put forward by Carlson and Putnam, since it can be understood as implicitly comprising the view that natural kinds are sorts or classes of entities “amenable to scientific investigation” (Carlson 1991: 370) or “of explanatory importance” (Putnam 1970a: 139); in a similar sense LaPorte claims that “a natural kind is a kind with explanatory value” (LaPorte 2004: 19).4 But to assert that natural kinds play an explanatory role can be considered as involving the claim that they appear in natural laws.⁵ In this regard it is worth noting that in some of his works after (1975d), and especially since (1983a), Putnam has presented what can be regarded as a definition of natural kind. According to this definition, conceived in (Putnam 1990: 68) rather as a condition for the ← 15 | 16 → adequacy of a criterion of natural kind-identity, an entity belongs to a natural kind if and only it obeys the same laws as the paradigmatic members of the kind (see Putnam 1983: 74), and two entities belong to the same natural kind if and only if they obey the same laws (Putnam 1990b: 68). From here the next definitions of natural kind and of natural kind term would follow: natural kinds are the kinds posited in laws and natural kind terms are the kind terms contained in laws.6 However, a caveat is advisable, namely, from this definition it follows that there are no vernacular terms that are natural kind terms, but many of the examples of the last sort of terms mentioned by Putnam and by other authors, like Kripke, are vernacular terms. Nevertheless, in this regard we can resort to Putnam’s claim that “in a prescientific period, these [i.e., the laws] may be low-level generalizations about observable characteristics” (Putnam 1990b: 59). Thus, vernacular terms, although they do not occur in laws and hence are not natural kind terms in the strict sense, they can be regarded as being so in a broad sense if they appear in this sort of low-level generalizations.

Notwithstanding, if we leave aside that caveat, in all disciplines in which there are laws there are natural kinds, and Putnam himself, in a talk with the author of this book, asserted that for an anthropologist, and hence from the point of view of anthropology, the term “culture” is a natural kind term. Thus, according to such definitions of natural kinds these involve very different types of entities and consequently there is a huge variety of terms that can be considered as natural kind terms.

There are still two groups of terms that in the debate concerning the reference of natural kind terms in contemporary Philosophy of Language have been regarded as prototypical natural kind terms. They are terms for biological kinds, e.g., “cat” and “tiger” – including terms for botanical kinds, like “elm” and “beech” –, and terms for kinds of material stuff and in particular for natural (chemical) substances, such as “water” and “gold”. Other terms that have been occasionally dealt with in that debate are physical magnitude terms and terms for diseases. All the same, given the diversity of the types of natural kind terms there is no guarantee that there will be a unitary semantic theory concerning them, and hence the extrapolation of a theory from one sort of natural kind ← 16 | 17 → term to another may turn out somewhat far-fetched. Nevertheless, the two types already mentioned as paradigmatic of natural kind terms, terms for biological species and for natural substances, are just the two types of natural kind terms mainly dealt with in the theories of S. Kripke and H. Putnam on natural kind terms, which have been in the centre of the contemporary semantic debate on this sort of terms. Notwithstanding, these authors reckon that the proposals on the reference of that type of terms will also apply in the main to the reference of physical magnitude terms, or in Kripke’s terminology, of natural phenomena terms; sometimes these authors tend to include these terms within natural kind terms and occasionally they regard them as a different class of terms, although related to the latter (see sections 4.1. and 5.4.; on Putnam’s theory of the reference of physical magnitude terms see this last section).

Nonetheless, concerning the two types of natural kind terms that have been regarded as prototypical, there is at least one reason to focus on terms for natural substances when dealing with the semantics of natural kind terms. This is because there is a plurality of conceptions on the notion of biological species which do not agree as to how species are to be individuated – see, e.g., Ereshefsky (2010) –, and consequently these conceptions involve possible disagreements concerning the reference of terms for species. In any case, in this book I will mainly take into consideration as examples of natural kind terms the terms for natural substances, using as paradigmatic instances the most frequent terms mentioned in Kripke’s and Putnam’s theories, that is, the natural substance terms “water” and “gold”. These examples of terms for natural substances (for chemical compounds and elements respectively) are among the terms principally used by those authors to illustrate and justify their reference theories on that sort of natural kind terms and of natural kind terms in general. Such type of terms has been denominated by many authors, Putnam among others, substance terms (or substance names),7 and I will usually employ this denomination in the following (see however chapter 1). In this regard it is worth noting that the starting point of Putnam’s theory on natural kind terms in most of the writings in which he puts forward his theory are precisely substance terms and especially the term “water”, on which we will focus. Furthermore concerning this sort of terms the definition or criterion of natural kind-identity by recourse to laws, according to which two entities belong to the same natural kind if and only if they obey the same laws, can be substituted ← 17 | 18 → by resorting to the microstructure, composition or underlying properties of the entities or samples of the substance in question – remember Putnam’s allusion to “deep-lying mechanisms” in (Putnam 1970a). Thus Putnam makes the following assertions: “‘has the same composition and (therefore) obeys the same laws’ becomes the criterion of substance-identity” (Putnam 1990: 60–61; emphasis added), “differences in microstructure invariably (in the actual world) result in differences in lawful behaviour” (1990: 69), “microstructure is what determines physical behaviour (laws of behaviour)” (ibid), and that in this way – by resorting to microstructure – “one […] reduces the vagueness of the ‘same laws’ criterion [for substance-identity]” (ibid), since “the notion of ‘same laws’ is, to be sure, somewhat vague” (1990: 68). The microstructure, composition or underlying properties in question will also be responsible for the low-level generalizations mentioned above.

Nevertheless, since Kripke’s and Putnam’s theories on substance terms constitute a particular case, although central, of their theories concerning natural kind terms, I will frequently stand at this more general level, although assuming that their considerations on natural kind terms in general should paradigmatically apply to substance terms.

Natural kind terms are usually regarded as general terms, and Kripke and Putnam conceive them in this way, and more precisely, which is explicit in Putnam’s case, as common nouns8 (or common noun phrases). General terms can be characterized by means of the notion of reference. A general term is a term whose function is not to refer to an individual, as it is the case with singular terms – among which are proper names – but to a set of individuals, which constitutes the extension of the term. There are other noteworthy views on general terms following which it should be distinguished between the reference and the extension of a general term. According to one of them the function of a general term is to refer not to a set of individuals, but to each and every individual of the set. In this second characterization, the notion of reference is usually employed at present as interchangeable with the notion of application, the extension of a ← 18 | 19 → general term being the set of the individuals to which the term applies (or the set of individuals the term is true of). A third conception envisages the function of a general term as referring to a universal (see sections 3.2. and 4.1.); in this case, the extension of a general term is the set whose members are the instances of the universal in question. In the following, I generally opt indistinctly for the two former characterizations of the reference of general terms, although in some chapters I will assume the third one. In any case, most assertions made using one of them can be reformulated in terms of either of the other two.

It is appropriate to point out that in the formulation of their theories both Kripke and Putnam, the initial advocates of the causal theory of the reference of natural kind terms, allude to other authors, generally preceding ones, with whom they disagree. On this matter it is noteworthy, on the one hand, Putnam’s discrepancy with J. Locke’s theory on natural kind terms. On the other hand, the opposition expressed by Kripke to the theory of J.S. Mill on general terms, to which Kripke assimilates Mill’s theory on natural kind terms, but it is also highly relevant the disagreement manifested by Kripke regarding the theories that would result from extending to general terms some theories of proper names, like those of G. Frege and B. Russell, as well as the ones of J. Searle and P.F. Strawson. Kripke considers the semantic theories of these authors, like the one by Mill, as descriptivist ones, but since they, unlike Mill, put forward their semantic theories mainly concerning proper names I will also take into consideration their theories on proper names and their extension to general terms, which would comprise that sort of general terms that natural kind terms are. Kripke’s extension of those authors’ theories on proper names to general terms, and particularly to natural kind terms, is probably due to the fact that Kripke’s theory on natural kind terms mainly stems from extending to these terms his theory on proper names. Thus, it is justifiable to include some chapters or sections on the theories of these other authors, in addition to the chapters devoted to Kripke’s and Putnam’s theories. However, we will also pay attention to other theories relevant to the present debate on the reference of natural kind terms, namely, to the theory proposed by M. Devitt and K. Sterelny (mainly by the first one) and to the view on reference put forward by F. Jackson, who is one of the most outstanding present advocates of the descriptivist theory and of a particular version of this theory, causal descriptivism.