The Periodic Table and the Philosophy of Classification There Are Many More Researchers in Classification Birger Hjørland Theory Than Those Listed Above

Knowl. Org. 38(2011)No.1 9 Forum: The Philosophy of Classification

Forum: The Philosophy of Classification

The Periodic Table and What is the Nature of the A Note on the Debate Between the Philosophy of Periodic Table as a Hjørland and Scerri on the Sig- Classification Classification System? nificance of the Periodic Table

Birger Hjørland Eric Scerri John Dupré

1.0 Introduction: This debate I would like to thank Professor Birger I am very grateful to Professor Birger Hjørland for his generous review of my Hjørland for giving me the opportu- Thanks to Professor Eric Scerri for en- book on the periodic table of the ele- nity to comment on his exchange with gaging in debate in this journal (Scerri ments (Hjørland 2008). As he states, Professor Eric Scerri on the periodic 2011) by replying to my review (Hjør- the periodic table represents perhaps table of the elements. However, since land 2008a) of his book (Scerri 2007). the strongest claim for a natural classi- Hjørland himself has provided a de- One of my points has been that we in fication that one can find in any disci- tailed commentary on Scerri’s response our community (Knowledge Organiza- pline. As such it is worthy of the atten- to his (Hjørland’s) review of Scerri’s tion, KO / Library and Information tion of scholars of classification and book on the topic, and since I am not Science, LIS) have been too isolated knowledge organization in general. I in an expert on the philosophy of chemis- from broader academic fields related to turn wish to compliment Hjørland for try, I shall limit myself to a few com- classification and the organization of promoting this interdisciplinary activity ments on what Scerri says about my knowledge. The present debate is a via his review and many previous writ- own views. (In fact one paragraph in a step towards reversing this situation. ings on the subject. I think that there is two page article on scientific classifica- Strangely enough, at the end of his re- much that can be learned from taking tion, and one footnote from my 1993 ply, Scerri (2011) seems to question this debate a little further. book, The Disorder of Things, most of (even) this view. In this connection he I now turn to some specific re- which are quoted in the discussion to seems, however, to confuse two differ- sponses to his book review. Hjørland date, as far as I can recall exhaust my ent things: 1) I have never said that the claims that classification should be, and published writing specifically on the periodic system has not influenced is in fact, based on pragmatic criteria topic of the periodic table.) LIS-classifications. On the contrary, I and thereby insists that even in the Scerri suggests that I am guilty of mentioned in my review two examples case of the periodic table, classification circularity in assuming that chemists (MEDLINE and UDC) which are is pragmatic rather than ‘natural.’ He aim at a structural analysis of matter clearly influenced by the periodic sys- also claims that the classification of and then find a classification based on tem. 2) What I did say was that books knowledge can be carried out by using structural elements suits this purpose. such as Scerri’s―and the broader field one of four approaches that he identi- It seems to me that my assumption of the philosophy of classification―are fies as empiricism, rationalism, histori- might be false, but hardly justifies a mostly ignored by scholars in KO/LIS. cism and pragmatism, of which he be- charge of circularity. I am happy to de- That people in KO seem to consider lieves the last to be the most “advanced fer to Scerri’s far greater expertise if he themselves “the professionals” in clas- theory.” Hjørland concedes (2008, 253) tells me it is false. However, I cannot sification (cf. Beghtol 2003), but that that the periodic system is: “probably accept his claim that chemists aim for the relation to the philosophy of classi- one of the most difficult classification “the analysis of matter period.” I do fication—as well as to specific scien- systems to defend from a pragmatist not believe there could be any such tific classification research—needs to point of view,” but adds that: “it is also thing. Matter has an enormous range be strengthened (cf., Hjørland & Ni- important to test our views against the of properties: macrostructural proper- colaisen 2004 and Nicolaisen & Hjør- most pre-eminent classifications if our ties such as strength, elasticity or hard- land 2004). arguments should be convincing.” ness; nutritional and toxicological

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Scerri points out that Hulme (1911) He presents his first line of attack on properties; aesthetic properties; and so is outdated; I am not, however, sup- the notion that the periodic system on. If there is such a thing as “analysis porting Hulme’s view about the irrele- classifies the elements as natural kinds period” it is, as the Greek etymology vance of the periodic system (and the in the following way. Hjørland points suggests, the breaking down of things philosophy of classification); on the out that although there may only exist into parts. Of course, chemists might contrary, I disagree, like Scerri, with one periodic law, there have been over have found that there were no such Hulme on this point―it was just men- 700 periodic tables published, which parts, that all kinds of stuff were ho- tioned to underline my view about the depend upon the particular pragmatic mogeneous and unanalysable, in which critical attitude towards the philosophy interests of any designer. My response case they would have had to content of classification in KO. That Hulme’s to this point would be to shift the dis- themselves with a rather unilluminat- paper is very old is an illustration of cussion to the periodic law rather than ing natural cataloguing of stuffs. The how difficult it is to identify more re- periodic tables, which as I am sure point is that there are many different cent discussions about the periodic Hjørland recognizes are attempts to enquiries that could be launched about system in the literature of KO. Hulme capture the more abstract periodic law. matter, and chemists are interested in was also named because he is known I do not believe that the failure of matter from a specific, perhaps funda- for the important principle of literary chemists to arrive at one commonly mental in some sense, perspective. warrant in KO and as the founder of agreed table, or representation, should This is the point about jade—not statistical bibliography, which is now be taken to mean that the elements that chemists don’t distinguish jadeite known as bibliometrics. themselves are not natural kinds or and nephrite, but that from another If Scerri wishes to prove me wrong that periodic classification is inherently perfectly respectable perspective they on this point, a proper argument would of a pragmatic nature. It may just be need not be distinguished, thus show- be to point to more recent texts and to that the current attempts at representa- ing that the perspective of chemistry is demonstrate how writings about the tion are infused with pragmatism since not the only one possible on matter. periodic system, about other scientific individual chemists may indeed be in- If gemology seems too unscientific classifications and about the philoso- terested in putting the periodic table to an activity to be relevant, one need only phy of classification have influenced particular uses rather than arriving at look to geology for classifications of theory and writings in KO and LIS one correct representation that reflects material stuff that follow a different (e.g., checking citations in LIS to this a natural classification. It is rather to path from those in chemistry. The min-

To say that a kind is natural is More philosophically speaking, “It is a classification system to say that it corresponds to a the identity and properties of which, once discovered, seems grouping or ordering that does any class of entities are some- inevitable.” not depend on humans. what separate issues eral olivine, one of the commonest sub- literature, e.g., by using Web of Science). the philosophy of chemistry, I suggest, stances on Earth, constituting a major I do not believe Scerri knows the litera- that one should look for the more gen- part of the Earth’s upper mantle, is re- ture of KO/LIS and that his denial of eral nature of the periodic law and the ferred to by the chemical formula my claim about the neglect of the lar- periodic table (Scerri 2009). (Mg,Fe)2SiO4. The parenthetical part of ger field of classification research in Hjørland turns to denying that ele- this formula indicates that olivine is a KO is valid. Much more relevant is ments are natural kinds more directly variable mixture of forsterite (Mg2Si Scerri’s view about the nature of the and quotes a recent book by Bryant as O4) and fayalite (Fe2SiO4). Of course periodic system (or periodic systems) a source of support. Bryant (2001, 88) one can describe the chemical composi- and the implications for the theory of writes: “even in the case of chemical tion of olivine; I have just done so. But classification, which are considered be- elements more than one kind of causal the reason that there olivine is a signifi- low. essentialism is scientifically legitimate.” cant category is not that it is a particu- Hjørland seems to counter Bryant’s lar mixture of chemicals, but that it 2.0 The emerging field “the philoso- claim by quoting from a review of her plays a crucial role in a description of phy of classification” book in which Stamos has shown con- the Earth’s structure and composition. vincingly that she (Bryant) is mistaken. (Compare brass or bronze, also variable Classification research is not just done Hjørland nevertheless seems to side mixtures of chemical substances—in within KO/LIS. Below are listed some with Bryant and the pragmatist ap- this case elements—the significance of important scholars in the interdiscipli- proach by further drawing upon the which derives entirely from metallurgy nary field which may be termed “phi- work of Dupré in order to adjudicate not chemistry.) losophy of classification” (or “theory between Bryant and her critical re- The other major component of the of classification,” “classification the- viewer, Stamos. Hjørland thus quotes upper mantle is referred to as pyroxene, ory,” “classification research,” “the sci- from Dupré (2006) who is comment- a large group of minerals with the gen- ence of classification,” etc.). There are ing specifically on the periodic table eral formula XY(Si,Al)2O6, where X and some philosophers who work with and who believes that there is: “much Y can be any of a wide range of cations, classification theory in general (e.g. potentially wrong with the supposition and (Si,Al) refers to a variable quantity Bunge 1983; Dupré 1993; Sutcliffe that there is a right way of classifying of silicon and aluminium. Many spe- 1993; Bryant 2001). A few philoso- things in the world,” and that: “the cific pyroxenes can be further identified phers who tend to specialize in the standard paradigm for such a successful and have more precise chemical compo-

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The Periodic Table and the Philosophy of Classification There are many more researchers in classification Birger Hjørland theory than those listed above. I have just tried to pro-

(continued from page 10) vide examples, not an exhaustive listing (there is a need for review articles in this interdisciplinary domain). classification of a specific field, e.g. biology The periodic system has a privileged place in the (Ereshefsky 2000; Hull 1998) or mental diseases philosophy of classification. Hubert Feger, for ex- (Cooper 2005). Then there are some scientists ap- ample, wrote (2001, 1967-1968; breaks with hanging proaching the field from an interest in classification indentations added): problems in their respective domains (e.g., in chemistry: Scerri 2007; in biology: Mishler 2000; Stevens A well known, still used, and expanding classifi- 1994; in social science: Marradi 1990 and Wallerstein cation is Mendelejew's Table of Elements. It can 1996). Then there are researchers approaching classi- be viewed as a prototype of all taxonomies in fication from mathematical, statistical or methodo- that it satisfies the following evaluative criteria: logical angles (e.g., in mathematics: Mirkin 1996; in statistical clustering: Hartigan 2001). Also many re- (a) Theoretical foundation: A theory deter- searchers in psychology, sociology, linguistics and mines the classes and their order. anthropology study how children and adults, lan- (b) Objectivity: The elements can be observed guages, social groups and cultures classify the world and classified by anybody familiar with the (e.g., in psychology: Keil 1989). table of elements. We have also KO researchers such as Anderson (c) Completeness: All elements find a unique (2003), Beghtol (2010), Gnoli (2006), Hjørland place in the system, and the system implies (2008d), Miksa (1994) and Szostak (2004) approach- a list of all possible elements. ing classification from the perspective of library and (d) Simplicity: Only a small amount of infor- information science, i.e. researching methods for ar- mation is used to establish the system and ranging books on shelves, for the construction of identify an object. subject catalogs, for information retrieval in biblio- (e) Predictions: The values of variables not graphical databases, for the construction of knowl- used for classification can be predicted edge organizing systems (KOS). This field may be (number of electrons and atomic weight), named bibliographical classification. It is about the as well as the existence of relations and of classification of recorded knowledge (documents in objects hitherto unobserved. Thus, the va- a wide sense). Beghtol (2010) uses the term “knowl- lidity of the classification system itself be- edge organization classification” for this field, but comes testable. LIS specialists are not the only professionals to deal with knowledge organization. Knowledge organiza- The examination of the periodic system may thus il- tion is primarily studied by scientists such as Scerri luminate core philosophical and theoretical issues in (the periodical system) or by philosophers, or by so- the philosophy of classification, which have largely ciologists. When LIS professionals classify a given been ignored by KO/LIS. They include: book, the concepts used are derived from the literature, not concepts and relations primarily con- – The concept of “Natural kind” structed by LIS-professionals. As Hulme (1911, 46- – The theory-laden nature of observations and its 47) said: “The real classifier of literature is the book- implication for classification theory wright, the so-called book classifier is merely the re- – The relation between classification and subject corder.” theory (such as, for example, the relation between Bibliographic classification has now expanded into the periodic system and theory of quantum me- concerns with technologies of automated classifica- chanics (QM) or the relation between the theory tion and to principles of ontologies, bibliometric of evolution and biological taxonomy) maps, folksonomies etc. Many computer scientists – Whether classifications are “correct” representa- are also contributing to this field (not to say domi- tions or more or less purposeful constructions nating it), among them Sebastiani (2005); and some – The methodological basis for construing classifi- philosophers such as Barry Smith (2004) are working cations (different epistemological ideals such as in the intersection between computer science and observation, logical analysis, historical reconstruc- philosophy in relation to principles of ontologies. tion or pragmatic analysis). 12 Knowl. Org. 38(2011)No.1 Forum: The Philosophy of Classification

I wish to make the following observations and con- swers; however, he does not discuss any alternative: clusions of this section: if he revealed his own position I would be in a better position to demonstrate why I think that historicism – The field of Philosophy of Classification is today and pragmatism are better grounded. very scattered and still rather limited as to the The pragmatic position is related to hermeneutics number of researchers and papers. It should be an (cf., Heelan & Schulkin 1998), which I regard as a phi- obvious goal to get it more integrated (by mutual losophy with the potential of contributing to the suc- citations). In all modesty I see my own book re- cessful practice of science. If a philosophy does not views (among other writings) as an attempt to es- have this potential, it seems difficult to justify it. tablish such a platform (e.g., Hjørland 2000, (However, Heelan (1998) in a paper about hermeneu- 2008a, 2008b, 2008c, 2009a). tics in natural science said that “we do not ask of a – Classification was downgraded by logical positiv- philosophy that it contribute to the successful practice ism because it was regarded as unscientific com- of science.” I disagree on this view, and I do think that pared with measurement (see Marradi 1990, Scerri also feels that his work on the philosophy of §3.2.1). If this is correct, then the fight for classi- chemistry should indeed contribute to the develop- fication implies also a fight against these positivist ment and to the successful practice of chemistry.) tendencies. Kuhn's book (1962/1996) The Structure of Scientific – KO would benefit very much if we were better in- Revolutions can be seen as an hermeneutic interpreta- tegrated with scholars in other fields and if jour- tion of the sciences because it conceives of scientists nals such as Knowledge Organization could pre- as governed by assumptions which are historically sent more of this interdisciplinary research. embedded and linguistically mediated activities organ- Hopefully our field may contribute by connecting ized around paradigms that direct the conceptualiza- different fields. tion and investigation of their studies. Scientific revolutions imply that one paradigm replaces another and 3.0 Epistemology and scientific methods introduces a new set of theories, approaches and defi- nitions. According to Mallery, Hurwitz and Duffy Any scientific classification has to be constructed (1992) the notion of a paradigm-centered scientific and verified by some methods. Even if we agree on community is analogous to Gadamer's notion of a lin- the superiority of a given classification (say the peri- guistically encoded social tradition. In this way her- odic table) we may still disagree in our interpretation meneutics challenges logical positivism. Observations of the scientific methods that ended up producing it. are always made on the background of theoretical as- Today there is no consensus concerning epistemol- sumptions: they are theory dependent. It should be ogy and scientific methodology. In the beginning of added that in my opinion pragmatism and hermeneu- the 20th century, logical positivism was the dominant tics are realist positions: People are developing their view. After 1962 Thomas Kuhn among others chal- ideas in a world that exists independently. Pragmatism lenged this view. It has also been challenged by her- is at the same time fallibilist: No scientific method is meneutics, pragmatism, feminist epistemology, critical able to guarantee the truth of knowledge claims. theory, postmodernism and other views. My main Scerri’s skepticism towards historicism and pragma- point here is that we cannot defend any claim properly tism is not unique. In an informal communication, the unless our arguments are based in an epistemology Swedish Professor Anders Ekholm wrote (30-07-2009 (that again needs to be defended). Therefore, we have 11:37, translated from Swedish. Eckholm’s own view to consider which epistemology we find useful. Other of classification can be seen in Ekholm (1996)): researchers may oppose a given view and forward an alternative view. The point is that there is no neutral You identify four main traditions within episte- position, and it is not possible to argue from a neutral mology: Empiricism, Rationalism, Historicism platform or from nowhere. The choice of epistemol- and Pragmatism. The first two are described by ogy is not a question of personal taste. It is a question Bunge [1983a+b] as the two main views, while of scientific truth. Therefore the task of working out a of epistemology the others should just be con- proper epistemology is a collective responsibility that sidered variations.… The discussion is interest- involves all scientists. ing but I tend to follow the view expressed by Scerri is obviously skeptical regarding my view Bunge that the first [historicism and pragma- that historicism and pragmatism are the best an- tism] after all are variations of the later [empiri- Knowl. Org. 38(2011)No.1 13 Forum: The Philosophy of Classification

cism and rationalism]. This is by the way also satisfactory in describing scientific progress. His- what Bunge says about his own view, which he toricism and pragmatism (as I understand these posi- describes in detail in vol. 6 [Bunge 1983b] under tions) are more satisfactory interpretations of what the label Scientific Realism (vol. 6:255). eminent scientists have done. Another way to express this is, as, for example, Dupré (1993) says: Sci- I cannot in this place provide a full analysis of the ence is a human activity and in the end it is evaluated views of Ekholm and Bunge. It would certainly be a by its contributions for human beings. The implica- good idea if somebody made an article in this journal tion is that a pragmatic factor is at play in science. which presented and examined Bunge’s view. In this On the other hand Kuhn (1962/1996) emphasized place I can just say that I do not believe that histori- that nature cannot be forced into any conceptual cism and pragmatism can be reduced to variations of structure that we provide. Nature makes resistance. empiricism and rationalism and that I consider the Our conceptual structures therefore―in the long latter insufficient. Probably my best arguments have run―have to adapt to reality. been put forwards in Hjørland (2009b). What is important for classification is that differ- Another criticism against (parts of) historicism ent methods tend to provide different classifications. If could be based on a view that has been expressed by the different methods and epistemologies led to the Cooper (2005, 48) based on Dupré: same classification, there would be no problem, of course. Nor can the essential property of a species be its evolutionary lineage. John Dupré [1981] – Empirists’ principles of classification emphasize: shows this in his paper “Natural Kinds and Bio- Classifications based on many properties which logical Taxa”. Relationships of ancestry cannot have been described in theory-independent ways; be the essential properties of species because – Rationalists’ principles of classification empha- “Any sorting procedure that is based on ances- size: The classifications that are logical coherent try presupposes that at some time in the past and based on clear principles; the ancestral organisms could have been sub- – Historicists’ principles of classification empha- jected to some kind of sorting” (p. 88). The size: a) (on the side of the objects): the classifica- point is that in order to make sense of claims tions that are systematically related to historical such as “Cats are the offspring of cats, while development of their elements;† and, b) (on the dogs are the offspring of dogs” one must have side of the subjects): classifications connected to some way of distinguishing the ancestor cats explicit theoretical views; from the ancestor dogs. Relations of ancestry – Pragmatists’ principles of classification empha- are only of any use once the parent organisms size: The classifications that are best suited for the have been sorted into kinds. As such, sorting purpose for which they are intended. (In 6.0 be- on the basis of ancestry must always be a sec- low I’ll introduce two different kinds of pragma- ondary, parasitic method of sorting. When we tism). are seeking the essential properties of species it is thus more appropriate to look to the basis of If these different approaches provide the same classi- the primary method of sorting, whatever it fication, we could speak of “natural kinds” in a sense might be, rather than to relations of ancestry.” of that term. They often provide, however, different classifications, as demonstrated in, for example, bio- If this analysis is correct it seems to affect not just logical taxonomy. How do we then decide which my view, but many others’ as well, e.g., Gnoli’s classification is the best? The pragmatic answer is (2006) phylogenetic classification and Hull’s (1998, that stability in our theories may arise after several 272), who wrote: “Two fundamentally different sorts iterations involving empirical, rational, theoretical of classification are those that reflect structural or- and pragmatic interacting considerations as a histori- ganization and those that are systematically related cal process. to historical development.” One of Scerri’s objections to the pragmatic view I cannot go much deeper into the specific implica- was that the individual scientists are not motivated tions for the scientific methods. The short reply is by pragmatic issues. This problem is addressed in that the traditional views (empiricism, rationalism 4.0. and their combination in logical positivism) are not 14 Knowl. Org. 38(2011)No.1 Forum: The Philosophy of Classification

†Scerri (2007, 250) presents Prout’s hypothe- describing medical effects and side effects? The claim sis, according to which all the elements are es- made by John Dupré is that the periodic system may sentially made out of hydrogen, and he writes: be extremely well suited to the tasks of general “The elements are now believed to have literally chemistry and that the general principle of the prag- evolved from hydrogen by various mecha- matic nature of classification can thus be “saved.” nisms.” Karpatschof (2000, 105) wrote: “Para- When Scerri writes: “More importantly, Dupré’s doxically, the most basic of all sciences, the sci- claim is somewhat circular. The aim of chemists is ences of pre-biological matter (i.e., the disci- not necessarily the structural analysis of matter but plines of astronomy, physics and chemistry) rather the analysis of matter period” ― I believe he were the latest to develop a theory of evolu- disregards that many different sciences are studying tion… The idea of eternal, immutable laws is “matter,” and therefore we should try to find out not easy to combine with the idea of develop- how they differ―and consequently how each of ment.” A simpler explanation may be that our them conceives and classifies the world. knowledge of the evolution of the universe In conclusion of this section: The individual scien- since the Big Bang is very recent and that this tists’ view of the world is shaped in cultural-historical knowledge is a prerequisite for an evolutionary and disciplinary contexts which influence their criteria theory in these fields. of, among other things, classification. The single sci- entist may be influenced by pragmatic factors whether 4.0 Individualism versus collectivism or not this is admitted in his writings or whether or not it is a conscious choice. Traditionally it has been Scerri argues that scientists are not motivated by the ideal for science to be objective and free of prag- pragmatic factors, they just want to find the truth. He matic influences, and therefore such influences may be also wrote: “Mendeleev, the chief architect of the peri- relatively hidden and thus hard to detect. odic system, repeatedly expressed his dislike for atomic theories....” Well, I believe that Thomas Kuhn 5.0 The concept of “element” in the periodic table has something important to say about this. He wrote (1996, 200): Scerri wrote: “Hjørland mentions the distinction between elements as simple substances (sense) and as To understand why science develops as it does, basic substances (reference) but in a different con- one need not unravel the details of biography text. As he sees it this distinction shows the coexis- and personality that lead each individual to a par- tence of the empiricist and rationalist approaches to ticular choice, though that topic has vast fascina- the classification of the elements. But in the very tion. What one must understand, however, is the next sentence this dual nature in the meaning of the manner in which a particular set of shared values term ‘element’ also becomes an example of the im- interacts with the particular experiences shared portance of the historicist approach to knowledge, by a community of specialists to ensure that although no reason is given for this claim. “ most members of the group will ultimately find Answer: I have formerly defined “concept” ac- one set of arguments rather than another deci- cording to my pragmatic understanding (Hjørland sive. 2009b, 1522-23):

The case for the pragmatic philosophy of science is Concepts are dynamically constructed and col- not primarily about the individual motives of scien- lectively negotiated meanings that classify the tists. It is about whether there are pragmatic factors world according to interests and theories. Con- involved in theory acceptance in the scientific com- cepts and their development cannot be under- munity. Whether, for example, astronomic theories stood in isolation from the interests and theories were accepted because they helped construe better that motivated their construction, and, in gen- calendars? Whether medical progress is determined eral, we should expect competing conceptions in part by its ability to cure people? In the case of and concepts to be at play in all domains at all the aim of chemistry: Whether there are divisions of times. labor between pure chemistry and, say, pharmacol- ogy, in which the first aims at describing more gen- In the same paper I argue that empiricist, rationalist, eral features, whereas the latter, in particular, aims at historicist and pragmatic concepts may compete in Knowl. Org. 38(2011)No.1 15 Forum: The Philosophy of Classification

any domain at any time. That implies that the notion quantum mechanics (QM) as a possible theoretical ba- of “element” in chemistry may vary. Scerri (2007) dis- sis. Scerri writes about those theories (2007, 24-25): cusses two conceptions of “element,” as simple substances and as basic substances. My interpretation is The first of these [Einstein’s theory of relativ- that the first sense corresponds with the empiricist ity] has had a limited impact of our under- ideal of defining terms, the second perhaps with a ra- standing of the periodic system but is becom- tionalist ideal. It should not be difficult to see what I ing increasingly important in accurate calcula- mean by the historicist and pragmatist view if you tions carried out on atoms and molecules; read my papers. It should not be difficult to follow the above definition of concept and apply it to “element.” and, The reason for my claim that Scerri asks for is this: Chemists cannot define “element” while disregarding The interesting question raised here is the rela- the theoretical developments in chemistry. When a tion between chemistry and modern atomic chemist (such as Scerri) looks at the world, he does so physics and, in particular, quantum mechanics. from the perspective of his chemical understanding. The popular view reinforced in most textbooks I can add that the discussion of the concept “spe- is that chemistry is nothing but physics “deep cies” in biology (often considered the element of bio- down” and that all chemical phenomena, and logical classification) is a really difficult discussion. especially the periodic system, can be developed on the basis of quantum mechanics. There 6.0 Classifications are theories are some problems with this view, however, (of what is being classified) which are considered in this book.

Philosopher Marion Bunge wrote about the relation For example, in chapter 9 it is suggested that between theory and classification (1983a, 330, em- the quantum mechanical explanation for the phasis in original): periodic system is still far from perfect. This is important because chemistry books, especially Classing and theorizing are then mutually textbooks aimed at teaching, tend to give the complementary activities. Categorization pre- impression that our current explanation of the cedes theorizing if only because every theory is periodic system is essentially complete. This is about some category of objects. In turn, theory not the case, or so it will be argued. allows one to refine the coarse and shallow pre- theoretical classifications. Moreover a classifi- Scerri also considered the influence of chemists, or cation is a theory of a kind. rather of inductive conclusions (p. 224):

Ereshefsky (2000) argued that the Linnaean Hierar- All this work was achieved without any argu- chy is an obsolete classification because it is not ments based on theoretical physics or, more spe- based on the theory of evolution. In a similar way we cifically, without using quantum theory. The should expect that any classification corresponds to a chemists’ configurations were obtained induc- theory and vice versa: Any theory has implications for tively on the basis of the chemical properties of the classification of its objects. Ørom (2003) demon- the elements. This aspect of the history of the strated how library classifications of arts are related periodic system is seldom emphasized, with to theories or paradigms of art. In the field of mental most accounts promoting the view that elec- diseases different theories are related to different tronic configurations resulted entirely from the classifications (cf., Cooper 2005). A given classifica- work of theoretical physicists such as Bohr. In tion (say DSMIV) may correspond to some views, truth, Bohr had also reached electronic configu- but is a bad reflection of, for example, the psycho- rations inductively, frequently drawing on analytic view (and thus a bad tool for psychoana- chemical evidence, at the chemists themselves lysts. Whether psychoanalysis itself is a bad theory is had done. another matter that has to been considered sepa- rately.) Where does this leave us regarding the question of the Concerning the periodic table, we may consider relation between a classification and a theory? It seems theories such as Einstein’s theory of relativity and that the periodic system has been constructed by the 16 Knowl. Org. 38(2011)No.1 Forum: The Philosophy of Classification

interaction of, in particular, chemists’ “inductive” view pose for which the table is used” (1, 3 p.136). The and quantum mechanics. I make the claim that this is question “Which periodic table is best?” is like not fact versus theory, but that this is (at the least) the question: “Which table of data in a Hand- two competing perspectives or” theories” (although book of Chemistry and Physics is best?” “Best they are interacting, mutually overlapping and proba- for what purpose(s)?” Display of<. Chemical bly still developing theories). My argument is based valencies? Trends in electronnegativity? Atomic on the premise that the idea of theory-neutral obser- structure? Secondary Periodicity? Secondary Kin- vation is hardly ever supported today; by implication ships? Tertiary Kinships? Gapless Periods? Peri- chemists—when making their observations and induc- ods’ complements of shells and subshells? Peri- tions—are conceptually mediated by the research tra- odicty’s dyadic character? Madelung’s Rule? Lo- dition in which they have been trained. Chemists’ cations of “problems elements”? Block-to-block views, I suppose, are influenced by the properties trends? The unique character of the s-block? which have been seen as most important in chemistry. No periodic table has all the features listed in The periodic law is itself a part of chemists’ theoretical Appendix XV. The question “Which periodic ta- luggage (the periodic law is a profound achievement in ble is best?” is as impossible as unnecessary to chemistry and physics because it links the internal answer. structure of the atoms with their bondage into molecules, their chemical interaction properties as well as Scerri (2009) in an article, the title of which has the with (some) physical features). following ending: “the Optimal Form of the Periodic In the overall pattern these views tend to support Table, if any” (emphasis added). This title thus opens each other, but, as Scerri argues, our current explana- the door for the possibility that there is not one opti- tion of the periodic system is not essentially complete. mal form of the periodic system. What is interesting is Could it be that there is not one perfect periodic sys- whether a specific theory such as quantum mechanics tem satisfying all views? And could it be that these tends to correspond better to a specific version? disagreements are related to different theories about In Wikipedia (2010) there is an article “Alternative chemical elements and the importance of different periodic tables”. These tables are based on the fact properties? Some authors emphasize the large number that not all correlations between the chemical ele- of periodic tables. Stewart, for example, wrote (2004, ments are effectively captured by the standard peri- 156): odic table:

Of the making of Periodic Tables there is no Alternative periodic tables are developed often end. No version can ever be definitive because to highlight or emphasize different chemical or there are various incompatible objectives. Some physical properties of the elements which are authors provide a schematic version that is not as apparent in traditional periodic tables. readable and easily reproduced, while others Some tables aim to emphasize both the nucleon exploit devices such as the third dimension to and electronic structure of atoms. This can be express complexity. Some aim at simplicity or done changing the spatial relationship or repre- grace while others want to convey detailed in- sentation each element has with respect to an- formation on such things as relative atomic other element in the table. Other tables aim to mass, valency, electronic structure, melting and emphasize the chemical element isolations by boiling points, electronegativity, radioactivity, humans over time. metallic or non-metallic nature, geological af- finities and so on. And an example:

The chemist Henry A. Bent wrote (2006, 108; em- Timmothy Stowe's physicist's periodic table phasis in original): [1988] is three-dimensional with the three axes representing the principal quantum number, Best periodic table? Because analogies among the orbital quantum number, and orbital magnetic elements are many-sided (Mendeleev), no peri- quantum number. odic table is superior to all other tables in all re- spects “There is no single best form of the peri- My question—as a non-expert in chemistry and odic table since the choice depends on the pur- physics—is: Could it be that the Stowe Periodic Ta- Knowl. Org. 38(2011)No.1 17 Forum: The Philosophy of Classification

ble, for example, simply is a better match with QM? Hjørland points out that although there may Scerri (2007) asks how well QM explains the peri- only exist one periodic law, there have been odic table, to what degree the periodic table can be over 700 periodic tables published, which de- reduced to QM. His way of asking—it seems to pend upon the particular pragmatic interests of me—presupposes that the periodic table is “given,” any designer. My response to this point would not something still being discussed and negotiated be to shift the discussion to the periodic law by scientists (in spite of what I quoted above about rather than periodic tables. the best form).) If it is correct that different theories (such as QM) tend to imply different versions of the If we substitute the expression “the periodic law” with periodic system, could this explain some of the al- “periodic theory,” I would expect that this is (at least ternative versions? Scerri does address this problem one) classification for which we are searching. (But (2007, 282), when saying: again: Chemical periodicity might be just one among more criteria by which it is relevant to construe a clas- Although one can partly agree with the view sification of chemical elements – and the concept of that different representations can help to con- element might itself be a problem depending on the vey different forms of information, I believe perspective.) Scerri suggests that “chemical periodic- that one may still maintain that one particular ity” is an objective fact and that one true classification representation reflects chemical periodicity, re- corresponds to this fact. But is everything about garded as an objective fact, in the best possible chemical periodicity clarified today? (The formulation manner. of the periodic law in Scerri (2007, 16) seems rather vague and thus open: “The periodic law states that af- And (2007, 286): ter certain regular but varying intervals the chemical elements show an approximate repetition in their It is with some trepidation that I advocate the properties.”) Why not say that there are theories of general adoption of the left-step periodic sys- chemical periodicity and that a given theory of chemi- tem since I am well aware of the resistance that cal periodicity corresponds to a certain classification? this proposal will meet, especially from the If it turns out that one theory may fully explain chemical community, which, rightly or chemical periodicity, then this theory implies a certain wrongly, regards itself as the sole proprietor of version of the periodic table. In other words: Chemi- the periodic system. cal classifications are implications of chemical theories (just as biological classifications, art classifications, It is important to say that I agree with Scerri that psychiatric classifications are implications of subject classifications should be based on the properties of theories in their respective fields). Scerri’s search for the elements (i.e. the principle of realism). The pos- one true classification should thus be understood as sible disagreement is about whether different sets of the search for one true theory of chemical periodicity. properties of the elements may provide fruitful dif- In this perspective the goal of the classification is to ferent classifications for different perspectives. correspond to a theory, and the search for one true Whether 1) chemical periodicity is only one classifi- classification is thus a trivial implication of the de- cation criterion among other and 2) Whether differ- mands that Scerri puts to it. ent kinds of chemical periodicity could be at play? It seems to me that Scerri makes a choice by giving 6.1 The narrower and broader form of pragmatism priority to some kinds of properties and regularities as compared to others. If so, it confirms my prag- At this point it seems important to make a distinc- matic understanding. (The quote above even reads as tion between pragmatism in a narrow and in a more if the social constructivists may have a point: The fundamental sense. Scerri (2010) did express that: struggle about the periodic system seems partly to reflect the interest of different social groups!). In the It may just be that the current attempts at rep- final page of Scerri (2007, 286) the criteria of beauty, resentation are infused with pragmatism since elegance and utility are briefly mentioned (but con- individual chemists may indeed be interested in sidered difficult and not discussed). Again, this is putting the periodic table to particular uses opening a door to the pragmatic perspective. rather than arriving at one correct representa- In his letter Scerri (2010) wrote: tion that reflects a natural classification. 18 Knowl. Org. 38(2011)No.1 Forum: The Philosophy of Classification

I agree that some versions of the periodic table may be Scerri (2007, 280) finds that the elements are natural short-term pragmatic for some purposes, but not kinds (and thus not a matter of convention), but pragmatic in the way of producing a better tool de- that “the criterion for membership to a group is by signed for basic science. The broader form of pragma- no means as clear-cut as that which distinguishes one tism should of course be linked to fundamental find- element from another.” He continues: “However, ings and theories and should be pragmatic for the fur- one may also argue that the placement of the ele- ther advancement of science. (I do not believe that ments into groups is not a matter of convention. If there is a great risk that pragmatism may be proven periodic relations are indeed objective properties, as wrong. If there is a risk, it probably is that pragmatism I argue here, it would seem to suggest that there is may turn out to become trivial or circular. Pragmatism one ideal periodic classification, regardless of cannot be opposed to the search for truth, but implies whether or not this may have been discovered.” that truth and relevance for the conduct of life are the John Dupré is probably one of the leading critics same, that universals are to be understood as both today of the view of natural kinds and natural classi- something ontological and pragmatic (see also Kar- fications as ordinarily understood. He writes, for ex- patschof 2000, 317-18, 366, and 447).) ample (1993, 274):

6.2 Conclusion of this section Atoms are often suggested as example of natural kinds, with atomic number serving as an es- The strength of the periodic system is, in particular, sential property. But the fate of cars driven over based on the periodic law, according to which proper- salted roads for any time provides a reminder ties of elements are periodic functions of their atomic that iron atoms are not at all the same as ferric numbers. Some of the open questions may be “how ions, although both have atomic number 26. many properties?” “which properties?” and “proper- Atoms are also said to vary with respect to ties important from which perspective?” Are the transitory states of orbital electrons, properties properties relevant for the classification of chemicals said to be of great significance to their chemical theory independent or reflecting a particular theory behavior. and interest? In the last case: Which competing perspectives/theories are at play, and which criteria It is important to realize that Dupré is also a realist should be used to decide and negotiate among them? in the sense that he classifies objects on the basis of their objective properties. He is however a pluralist 7.0 Natural classification, realism, natural kinds (or “promiscuous”) realist in claiming that there is and essentialism more than one way to “carve nature at its joints.” This seems to be related to the view expressed by The concept “natural kind” is important in the phi- Marradi 1990, 3.1): losophy of classification. To say that a kind is natural is to say that it corresponds to a grouping or order- The opposition between “natural” and “artifi- ing that does not depend on humans. The idea of cial” classification is a recurring theme in the natural kinds may also be expressed by Plato’s meta- last two centuries. Cohen and Nagel have co- phor "carving nature at its joints." Again chemical gently argued that “any division ... according to elements play an important role because other can- some actual trait arbitrarily chosen is perfectly didates for the term (such as biological species) have natural ... [but it] may also be said to be artifi- turned out to be problematic examples. In the peri- cial, in the sense that we select the trait. odic system there may be different claims about natural kinds: Traditional accounts of natural kinds centre on ideas of “essences” or “essential properties”. Wikipedia – That the single element (such as gold (element # (2010-06-06) defines “essence” the following way: 79) or iron (element #26)) are natural kinds; – The extension of this view to more complex chemi- In philosophy, essence is the attribute or set of cal structures (such as molecules); and, attributes that make an object or substance – That the elements group naturally into classes of what it fundamentally is, and which it has by elements (such as noble gases, alkali metals and necessity, and without which it loses its iden- the halogens). tity. Essence is contrasted with accident: a Knowl. Org. 38(2011)No.1 19 Forum: The Philosophy of Classification

property that the object or substance has con- ence and the practice of information science are thus tingently, without which the substance can still seen as more constructive. The periodic system retain its identity. seems to be the ultimate challenge to this view. I do not believe the last word has been said about this Cooper (2005, 47) wrote: important problem, but this article has tried to bring the KO-community up-to-date in relation to what I In recent years traditional essentialist accounts see as a fundamental problem in our field. of natural kinds have come in for fierce criticism. A major difficulty is that for biological species, References which are traditionally considered amongst the best examples of natural kinds, no plausible can- Anderson, James D. 2003. Organization of knowl- didates for the essences can be found. Several edge. In Feather, John and Sturges, Paul, eds., In- different criteria may be employed by biologists ternational encyclopedia of information and library seeking to delineate species: morphological fea- science, 2nd. ed. London: Routledge, pp. 471-90. tures, evolutionary lineage, the criteria of repro- Arabie, Phipps; Hubert, Lawrence J. and de Soete, ductive isolation, or genetic features. On exami- Geert, eds. 1996. Clustering and classification. Sin- nation none of these appear suitable candidates gapore: World Scientific Publishing Co. Pte. Ltd. for being the essential properties of biological http://books.google.dk/books?id=AgovP9eJPs species. UC& Barthes, Roland. 1967. The death of the author. Aspen A reasonable position may be that “essential proper- no. 5-6 http://www.ubu.com/aspen/aspen5and6/ ties” are essential from a given theoretical perspec- threeEssays.html#barthes tive. To the degree that there are competing perspec- Beghtol, Clare. 2003. Classification for information tives, there will be competing views of which proper- retrieval and classification for knowledge discovery: ties are essential. Relationships between “professional” and “naïve” classifications. Knowledge organization 30: 64-73. 8.0 Conclusion Bent, Henry A. 2006. New ideas in chemistry from fresh energy for the periodic law. Bloomington, IN: In Hjørland (2008d) I provided the following model AuthorHouse. for “the traditional view of classification” in KO: Beghtol, Clare. 2010. Classification Theory. In Bates, Marcia and Maack, Mary Niles, eds., Encyclopedia Scientific Classification → Library classification (KO) of Library and Information Sciences, 3rd ed. Boca Raton: CRC Press, pp. 1045-60. This view may be expressed by stating that there is Bryant, Rebecca. 2001. Discovery and decision: ex- only one way in which nature has joints or by saying ploring the metaphysics and epistemology of scien- “nature itself has supplied the causal monistic essen- tific classification. Madison, NJ : Fairleigh Dickin- tialism. Scientists in their turn have simply discovered son University Press. and followed (where ‘simply’ ≠ ‘easily’)” (Stamos Bunge, Mario. 1983a. Treatise on basic philosophy. 2004, 138-139). Library and information scientists in Vol. 5: Epistemology & methodology I: Exploring the turn have to study scientific classifications and “sim- world. Dordrecht: D. Reidel Publishing Company. ply discover and follow” scientific classifications. This Bunge, Mario. 1983b. Treatise on basic philosophy. view has, however, almost disappeared in KO in the Vol. 6: Epistemology & methodology II: Under- second half of the 20th century (to be ousted by, for standing the world. Dordrecht: D. Reidel Publish- example, facet-analytic and use-oriented perspectives). ing Company. (My own position is thus closer to this traditional Cohen, Morris Raphael & Nagel, Ernst. 1934. An in- view compared to, for example, facet-analytic, user- troduction to logic and scientific method. New oriented and cognitive views.) York: Harcourt. Against this traditional view may be put the view Cooper, Rachel. 2005. Classifying madness. A phi- that classifications are reflecting the purposes for losophical examination of the Diagnostic and Sta- which they are designed and that different sciences, tistical Manual of Mental Disorders. Berlin: theories and human activities classify the world Springer. (more or less) differently. Both the practice of sci- 20 Knowl. Org. 38(2011)No.1 Forum: The Philosophy of Classification

Dupré, John. 1981. Natural kinds and biological comment to Beghtol (2003). Knowledge organiza- taxa. The philosophical review XC: 66-90. tion 31: 55-61. Dupré, John. 1993. The disorder of things: Metaphysi- Hjørland, Birger & Nissen Pedersen, Karsten. 2005. A cal foundations for the disunity of science. Cam- substantive theory of classification for information bridge, MA: Harvard University Press. retrieval. Journal of documentation 61: 582-97. Ekholm, Anders. 1996. A conceptual framework for Hull, David L. 1998. Taxonomy. In Craig, Edward classification of construction works. ITcon 1: 1- ed., Routledge encyclopedia of philosophy CD- 25. http://www.itcon.org/1996/2/paper.pdf ROM Version 1.0. London: Routledge. Ereshefsky, Marc. 2000. The poverty of the Linnaean Hulme, E. Wyndham. 1911. Principles of book clas- Hierarchy : A philosophical study of biological tax- sification. Library Association Record, 13: 354-58; onomy. Cambridge: Cambridge University Press. 389-94; 444-49. Feger, Hubert. 2001. Classification: Conceptions in Karpatschof, Benny. 2000. Human activity: Contribu- the social sciences. In Smelser, Neil J. and Baltes, tions to the anthropological Sciences from a perspec- Paul B. eds., International encyclopedia of the social tive of activity theory. Copenhagen: Dansk Psykolo- and behavioral sciences. New York: Elsevier, pp. gisk Forlag. Available in fultext from: http:// 1966-73. informationr.net/ir/12-3/Karpatschof/Karp00.html Gnoli, Claudio. 2006. Phylogenetic classification. Keil, F. 1989. Concepts, kinds, and cognitive develop- Knowledge organization 33: 138-52. ment. Cambridge, MA: MIT Press Hartigan, J. A. 2001. Statistical Clustering. In Smel- Kuhn, Thomas S. 1962/1996. The structure of scien- ser, Neil J. and Baltes, Paul B. eds., International tific revolutions. 3rd ed. Chicago: The University encyclopedia of the social and behavioral sciences. of Chicago Press, 1996. New York: Elsevier, pp. 15014-19. Mallery, John C.; Hurwitz, Roger and Duffy, Gavan. Heelan, Patrick A. 1998. The scope of hermeneutics 1992. Hermeneutics. In Shapiro, Stuart C. ed., in natural science. Studies in the history and phi- Encyclopedia of artificial intelligence, 2nd ed. New losophy of science 29: 273-98. York: John Wiley & Sons, pp. 596-611. Heelan, Patrick A. & Schulkin, Jay. 1998. Herme- Marradi, Alberto. 1990. Classification, typology, neutical philosophy and pragmatism: A philoso- taxonomy. Quality and quantity 24, 2: 129-57. phy of science. Synthese 115: 269–302 http://www. Available at: http://web.archive.org/web/2004070 springerlink.com/content/p506nl6315121r45/ 5070709/http://www.unibo.edu.ar/marradi/ fulltext.pdf classqq.pdf Hjørland, Birger. 2008a. Review of The periodic table: Miksa, Francis L. 1994. Classification. In Wiegand, Its story and its significance. By Eric Scerri. Knowl- Wayne A and Davis, Donald G., Jr., eds., Encyclo- edge organization 35: 251-55. pedia of library history. New York: Garland Pub- Hjørland, Birger. 2008b. Review of The poverty of the lishing, Inc., pp. 144-53. Linnaean hierarchy: A philosophical study of bio- Mirkin, Boris. 1996. Mathematical classification and logical taxonomy, by Marc Erevsky. Knowledge or- clustering. Dordrecht: Kluwer Academic Publishers. ganization 35: 255-59. Mishler, B. D. 2000. Deep phylogenetic relationships Hjørland, Birger. 2008c. Review of Classifying mad- among “plants” and their implications for classifi- ness: A philosophical examination of the Diagnostic cation. Taxon 49: 661-83. and statistical manual of mental disorders. Knowl- Nicolaisen, Jeppe and Hjørland, Birger. 2004. A re- edge organization 35: 259-63. joinder to Beghtol (2004). Knowledge organization Hjørland, Birger. 2008d. What is knowledge organi- 31: 199-201. zation (KO)? Knowledge organization 35: 86-101. Ørom, Anders. 2003. Knowledge organization in the Hjørland, Birger. 2009a. Review of Theories of geo- domain of art studies: History, transition and con- graphic concepts: Ontological approaches to seman- ceptual changes. Knowledge organization 30: 128-43. tic integration, by Marinos Kavouras and Margarita Sayer, R. Andrew. 1992. Method in social science: A Kokla. Knowledge organization 36: 178-80. realist approach. London: Routledge. Hjørland, Birger. 2009b. Concept theory. Journal of Scerri, Eric. 2005. Some aspects of the metaphysics the American Society for Information Science and of chemistry and the nature of the elements. Te c h n o l o g y 60: 1519-36. HYLE--International journal for philosophy of Hjørland, Birger and Nicolaisen, Jeppe. 2004. Scien- chemistry 11(2): 127-45 http://www.hyle.org/ tific and scholarly classifications are not “naïve”: a journal/issues/11-2/scerri.htm Knowl. Org. 38(2011)No.1 21 Forum: The Philosophy of Classification

Scerri, Eric. 2007. The periodic table, its story and its Stevens, Peter F. 1994. The development of biological significance. Oxford: Oxford University Press. systematics: Antoine-Laurent de Jussieu, nature and Scerri, Eric. 2009. The dual sense of the term “ele- the natural system. New York: Columbia University ment,” attempts to derive the Madelung Rule and Press. the optimal form of the periodic table, if any. Inter- Stewart, P. 2004. A new image of the periodic table. national journal of quantum chemistry 109: 959–71. Education in chemistry 6: 156-58. Scerri, Eric. 2011. What is the nature of the periodic Sutcliffe, J. P. 1993. Concept, class, and category in table as a classification system? Knowledge organi- the tradition of Aristotle. In Van Mechelen, Iven zation 38 (this issue). et al., eds., Categories and concepts. London: Aca- Sebastiani, Fabrizio. 2005. Text categorization. In demic Press, pp. 35-65. Zanasi, Alessandro, ed., Text mining and its appli- Szostak, Rick. 2004. Classifying science, phenomena, cations. Southampton, UK: WIT Press, pp. 109- data, theory, method, practice. Berlin: Springer. 29. Retrieved 2010-01-23 from: http://nmis.isti. Wallerstein, Immanuel M. 1996. Open the social sci- cnr.it/sebastiani/Publications/TM05.pdf ences; Report of the Gulbenkian Commission on the Smith, Barry. 2004. Beyond concepts: Ontology as Restructuring of the Social Sciences. Stanford, reality representation. In Varzi, Achille and Vieu, Calif.: Stanford University Press. Laure, eds., Formal Ontology and Information Sys- Wikipedia. The free encyclopedia. Alternative periodic tems: Proceedings of the Third International Con- tables. Retrieved 2010-06-01 from: http://en.wiki ference (FOIS 2004). Amsterdam: IOS Press, pp. pedia.org/wiki/Alternative_periodic_tables 73–84. http://ontology.buffalo.edu/bfo/Beyond Concepts.pdf Stamos, David N. 2004. Review of Discovery and de- Contact: cision: Exploring the metaphysics and epistemology Royal School of Library and Information Science, of scientific classification by Rebecca Bryant. Phi- 6 Birketinget, DK-2300 Copenhagen S, Denmark losophical psychology 17: 135-39.

What is the Nature of the never accepted the discovery of the electron that Periodic Table as a Classification System? took place in 1897, a full ten years before his death Eric Scerri in 1907. More importantly, Dupré’s claim is somewhat cir- (continued from page 10) cular. The aim of chemists is not necessarily the scientific classification is the periodic table of the structural analysis of matter but rather the analysis of elements.” Dupré claims that the chemists’ belief matter period. It so happens that the analysis of mat- that they have arrived at an ideal classification is an ter in general later revealed that a structural ap- illusion, “because of the specific aims implicit in the proach, in terms of atoms, protons and electrons, history of chemistry.” was a fruitful path to adopt. The chemists did not So what are these specific aims that chemists ap- impose a structural prejudice upon chemical analysis. parently possess and that have rendered their classi- The latter is a feature that arose, presumably because fication system biased in some way? Dupré considers the world itself contains discrete structural compo- that it is because chemists aim at the structural nents such as atoms and electrons. Dupré further analysis of matter and: “If, as appears to be the case, confuses the issue by quoting from LaPorte’s well all matter is composed of a small number of struc- known article on natural kinds where LaPorte re- tural elements, a classification based on those ele- ports that the Chinese jade carvers refer to two quite ments will be best suited to those purposes.” distinct chemicals as “jade.” I regard this as irrelevant I think that Dupré as well as Hjørland, who since it is not the views of Chinese carvers that are quotes him approvingly, are incorrect for two rea- under discussion but that of scientists. Scientists do sons. First of all, the periodic system of classification not refer to the two kinds of materials as “jade” but was arrived at completely independently of any con- as jadeite and nephrite as LaPorte readily acknowl- ception of structure, atomic or otherwise. Men- edges. deleev, the chief architect of the periodic system, re- Hjørland proceeds to discussing what he calls peatedly expressed his dislike for atomic theories and “four possible ways” to defend the pragmatic view of 22 Knowl. Org. 38(2011)No.1 Forum: The Philosophy of Classification

classification. The first is that at least certain features in favor of its generality rather than specificity. Hjør- of the periodic system are still open to debate, a land even questions whether atomic number should claim made with no further elaboration. But surely be considered as a criterion of natural kinds because, this is a weak argument since there is no field of sci- “not all properties are predicted by atomic number.” ence that is devoid of debate. The mere presence of This is of course true but irrelevant. Whether or not debates, of some form or other, does not provide an element is a superconductor, for example, cannot sufficient warrant for believing that one must hold a be predicted from its atomic number but this has lit- pragmatic view of knowledge rather than believing in tle bearing on whether or not elements are identified the existence of natural kinds in a particular field of via their atomic numbers. Why should all properties science. of an element be predictable directly from just The second of Hjørland’s reasons is a direct ap- atomic number? As I just mentioned, some proper- peal to Dupré as quoted above, namely that the ties including superconductivity cannot be predicted pragmatic nature of the periodic system is due to the from a knowledge of the element’s atomic number. purpose of chemistry which Dupré takes to be the This fact does little to shake the confidence that structural analysis of matter. I would counter this by chemists and physicists have in the notion that the rephrasing what I said earlier. The aim of chemistry identity of a particular element resides in the value of is to understand the nature of matter by whatever its atomic number. means necessary. It is not to impose a structural con- More philosophically speaking, the identity and ception at the very outset of the enterprise. properties of any class of entities are somewhat sepa- The third reason given by Hjørland (2008, 253) rate issues. In the modern understanding of the term reads as follows: “The third [reason] is to operate ‘element’ for example, the identity of gold does not with very general purposes for the sciences, in which reside in its being a certain color or possessing a case an ideal classification can be understood as the shiny appearance or indeed in displaying any particu- best tool with which mankind can control nature.” lar ‘property’ as such but just it its having an atomic Once again this conclusion is too quick since it does number of 79. Many philosophers of science who not argue for science being a tool, or that science espouse the causal theory of reference are in agree- aims to control nature, but merely asserts these ment with this view in claiming that identity is given claims as facts. by focusing on ‘reference’ rather than ‘sense,’ or on The fourth and final way in which Hjørland re- the essential qualities rather than the properties of an gards the periodic system as a being pragmatically element (Putnam 1975; Scerri 2005). driven, rather than a reflection of natural kinds, is by Hjørland mentions the distinction between ele- questioning what he terms, “the generality of the pe- ments as simple substances (sense) and as basic sub- riodic system’s organization of similar elements.” stances (reference) but in a different context. As he Hjørland claims that different chemical specialties sees it this distinction shows the coexistence of the such as agro-chemistry or food chemistry may be empiricist and rationalist approaches to the classifi- somewhat opposed to each other in seeking to high- cation of the elements. But in the very next sentence light different aspects of the behavior of the chemi- this dual nature in the meaning of the term ‘element’ cal elements. He says that the periodic system seems also becomes an example of the importance of the somewhat opposed to such “social classifications” by historicist approach to knowledge, although no rea- different kinds of chemists, which he takes to a limit son is given for this claim. to the prediction of properties by the periodic sys- Fourthly, we are told that the pragmatist view is tem itself. exemplified by another aspect of the periodic table, This conclusion is rather puzzling to the present namely, “the weight attributed to chemical respective author since it is precisely because the periodic table physical properties when determining the similarities seeks the most general possible description and rela- among the elements.” I hope that Hjørland might be tionships among the elements that it may not imme- prepared to explain this statement more fully as I am diately yield the kinds of predictions that are useful confused as to its meaning. Similarly, I would ask the to agro-chemists or food chemists. But if this situa- author to clarify the meaning of the next claim, tion is the case, then I would say, so much the worse namely that the attempts to reduce chemistry to for the demands of these professions and that it is quantum mechanics, that I discuss in my book, are not a reason for questioning the generality of the pe- indicative of the pragmatic approach to knowledge. riodic table. If anything it is a graphic demonstration Knowl. Org. 38(2011)No.1 23 Forum: The Philosophy of Classification

Finally, Hjørland examines whether a classification, References such as the periodic system, that is first developed in science, can then spread into the public media and into Bryant, Rebecca. 2001. Discovery and decision: ex- library classification systems. His conclusion seems to ploring the metaphysics and epistemology of scien- be that the periodic system has had no influence in tific classification, Madison, NJ: Fairleigh Dickin- these fields because books on the periodic table, such son University Press. as the one he is reviewing, are largely ignored in the Dupré, John. 2006. Scientific classification. Theory, field of knowledge organization. Hjørland quotes culture & society 23 (2/3): 320-32. from a rather outdated source, written no less than 99 Hjørland, Birger. 2008. Book Review of Eric Scerri, years ago, in which the originator of the principle of The Periodic Table, its story and its significance. “literary warrant” bemoans the fact that the periodic Knowledge organization 35: 251-55. system is merely a classification by the names of ele- Hulme, E. Wyndam. 1911. Principles of book classi- ments which was of course incorrect then as it is now. fication. Library Association record 13: 354-58, This quoted author, Hulme (1911), also contends Oct 1911; 389-94, Nov 1911; 444-49, Dec 1911. that, practically no literature in book form exists con- Putnam, Hilary. 1975. The Meaning of “Meaning” in, cerning the elements because, “no monograph, for in- Philosophical papers, vol. 2. Cambridge: Cam- stance has yet been published on the chemistry of iron bridge University Press. or gold.” These days there are literally dozens of Scerri, Eric. 2008. Collected papers on the philosophy books on these two elements alone and so would seem of chemistry. London: Imperial College Press. to preclude any conclusions on the nature of classifi- Scerri, Eric. 2005. Some aspects of the metaphysics cation based on Hulme’s writings of 1911. of chemistry and the nature of the elements. Hyle, To conclude, I thank Hjørland for his complimen- International journal for the philosophy of chemistry tary remarks about my book in the course of his re- 11: 127-45. view but I must disagree with his characterization of the periodic system as being the result of pragmatism rather than the way the world of the chemical Contact: elements is actually ‘carved at the joints.’ I am look- Department of Chemistry & Biochemistry, UCLA, ing forward to his response and to his clarifying the Los Angeles, CA 90095, USA parts of his review that I did not fully comprehend.

A Note on the Debate Between Hjørland and Scerri piece of jade rather than an impure one. The point, of on the Significance of the Periodic Table John Dupré course, is that jadeite is a geological term not a chemical term. Many of its properties may be explained by (continued from page 10) (more or less constant) features of its chemical compo- sitions, for example jadeite, NaAlSi2O6. Although this sition. But the category, as with olivine or pyroxene, is last looks like an exact chemical formula, it would be a shaped by the concerns of geology. The point would be mistake to suppose that jadeite was, primarily or essen- even clearer for such much more chemically variable tially, the name of a chemical kind. To be a jadite (or substances as magma (from which the rocks just dis- jadetite) rock is to be a rock with a specific predomi- cussed are originally formed), tephra, or lava. nant composition produced through a characteristic Analytic chemistry, then, is not the only basis for metamorphic process at certain ranges of pressure and the classification of kinds of stuff. Scerri is right to see temperature. Relatively small differences in composi- the periodic table as the hardest test case for pluralistic tion produce a variety of colours as well as difference in accounts of kinds, and it has generally been recognised physical properties such as density. It would be quite as such by pluralists including myself. It is a classifica- wrong to think that a piece of jadeite with particular tion system which, once discovered, seems inevitable; chemical traces that imparted to it a particular shade of it strikes many as embodying the discovery of that green was thereby impure jadeite (or, indeed, impure feature of a material stuff whereby, in Locke’s memo- jade). The presence of such traces is characteristic of rable phrase, it is what it is. A possible response by the jadeite and particular colour-producing traces might, pluralist is to acknowledge that this is an exception to indeed, make a piece of jadeite an exceptionally fine the pluralism that becomes irresistible for the more 24 Knowl. Org. 38(2011)No.1 Forum: The Philosophy of Classification

complex domains of biology and society. (As David elegance, is no threat to a thoroughgoing pluralism, Hull once chided me, a pluralist should not be com- or to the pragmatist attitude that inspires it. mited to a monistic (i.e. monistically pluralist) metaphysics.) Nevertheless, I think there is no reason for References the pluralist to be so concessionary). The chemistry based on the periodic table is a rightly admired scien- Dupré, John. 1993. The disorder of things: Metaphysi- tific project, one of the landmark successes of modern cal foundations for the disunity of science. Cam- science. Nonetheless, it does not provide the only way bridge, MA: Harvard University Press. of classifying material stuff. Geology, I have suggested, Hjørland, Birger. 2008. Book Review of Eric Scerri, provides a clear example of a science the concerns and The Periodic Table, its story and its significance. classifications of which do not align exactly with those Knowledge organization 35: 251-55. of chemistry. Metallurgy, as I briefly mentioned, is an- Scerri, Eric. 2007. The periodic table, its story and its other. Crystallography and parts of astronomy or significance. Oxford: Oxford University Press. fluid mechanics may be others. And most important, we should not rule out the possibility that we will in the future develop quite new interests in the classifica- Contact: tion of matter. ESRC Centre for Genomics in Society (Egenis), In short, then, I concur fully with Hjørland’s in- Byrne House, St. German's Road, University of Exe- sistence that the periodic table, for all its power and ter, Exeter EX4 4PJ