Natural kind essentialism is a specification of the intuitive idea that there are some mind-independent or objective categories in nature. These categories are thought to be characterised by a shared essence, which may involve intrinsic or extrinsic properties, mechanisms, or causal history. While the ontological basis of natural kinds has its roots in antiquity and especially Aristotle, the contemporary notion of a “natural kind” in philosophical discussion is often traced to William Whewell’s and John Stuart Mill’s work in the 1800s. (...) In its more modern form, natural kind essentialism was popularised in the 1970s mainly by Saul Kripke and Hilary Putnam. Traditionally, natural kind essentialism has been associated with intrinsic and microstructural properties, but contemporary work has made it clear that more refined versions of natural kind essentialism may have to accept extrinsic or relational essences. (shrink)

Are acids natural kinds? Or are they merely relevant kinds? Although acidity has been one of the oldest and most important concepts in chemistry, surprisingly little ink has been spilled on the natural kind question. I approach the question from the perspective of microstructural essentialism. After explaining why both Brønsted acids and Lewis acids are considered functional kinds, I address the challenges of multiple realization and multiple determination. Contra Manafu and Hendry, I argue that the stereotypical properties of acids are (...) not multiply realized. Instead, given the equivalence between the proton-donating and electron-accepting mechanisms of Brønsted and Lewis, respectively, I show that acidity as a property type can be identified with a unique microstructural property, namely the presence of a LUMO or other low energy empty orbital. In doing so, I defend the view that the Lewis theory encompasses Brønsted–Lowry, and that all Brønsted acids are also Lewis acids. Contra Hacking and Chang, I thus maintain that the different concepts of acidity do not crosscut, and that the hierarchy requirement is met. Finally, by characterizing natural kinds as powerful objects and by adopting a dispositional view of functions, I illustrate how the microessentialist can make sense of the latent and relational character of most acids. In sum, I contend that acids are genuine natural kinds, even for the microstructural essentialist. (shrink)

Kripke-Putnam argument for natural kind essentialism can be said to depend on placeholder essentialist intuitions. But some argue that such philosophical intuitions are merely preschooler cognitive biases which are not supported by scientific knowledge of natural kinds. Chemical substances, for instance, whether elements or compounds do not have such privileged set of underlying properties (‘same substance’ relation) which are present in all members of the kind and which provide necessary and sufficient condition for kind membership. In this paper, I argue (...) that placeholder essentialism works for at least some of the scientific natural kinds especially for the basic chemical natural kind, i.e., element. I argue that the dual sense of the element (the basic substance and the simple substance) along with microstructuralism helps explain the essence of an element not only at the abstract level but also at the more concrete level. Based on this essentialist account of element, I conclude that placeholder essentialism is not completely without merit, and it fits nicely with at least some of our scientific natural kinds. (shrink)

Philosophers have often debated the truth of microstructural essentialism about chemical substances: whether or not the structure of a chemical substance at the molecular scale is what makes it the substance it is. Oddly they have tended to pursue this debate without identifying what a structure is, and with some confusion and about what a chemical substance is. In this paper I draw on chemistry to rectify those omissions, providing a pluralist account of structure, clarifying what (according to chemistry) a (...) chemical substance is and defending microstructural essentialism, as I understand that position. I then give an account of the existence of composite substances and objects in chemistry, an issue that goes back to Aristotle. (shrink)

Are acids natural kinds? Or are they merely relevant kinds? Although acidity has been one of the oldest and most important concepts in chemistry, surprisingly little ink has been spilled on the natural kind question. I approach the question from the perspective of microstructural essentialism. After explaining why both Brønsted acids and Lewis acids are considered functional kinds, I address the challenges of multiple realization and multiple determination. Contra Manafu and Hendry, I argue that the stereotypical properties of acids are (...) not multiply realized. Instead, given the equivalence between the proton-donating and electron-accepting mechanisms of Brønsted and Lewis, respectively, I show that acidity as a property type can be identified with a unique microstructural property, namely the presence of a LUMO or other low energy empty orbital. In doing so, I defend the view that the Lewis theory encompasses Brønsted--Lowry, and that all Brønsted acids are also Lewis acids. Contra Hacking and Chang, I thus maintain that the different concepts of acidity do not crosscut, and that the hierarchy requirement is met. Finally, by characterizing natural kinds as powerful objects and by adopting a dispositional view of functions, I illustrate how the microessentialist can make sense of the latent and relational character of most acids. In sum, I contend that acids are genuine natural kinds, even for the microstructural essentialist. (shrink)

The new externalist picture of natural kind terms due to Kripke, Putnam, and others has become quite popular in philosophy. Many philosophers of science have remained sceptical. Häggqvist and Wikforss have recently criticised this view severely. They contend it depends essentially on a micro-essentialist view of natural kinds that is widely rejected among philosophers of science, and that a scientifically reasonable metaphysics entails the resurrection of some version of descriptivism. It is argued in this paper that the situation is not (...) quite as dark for the new theory of reference as many critics suggest. There are several distinct questions here which should not be conflated and ought to be dealt with one by one. Descriptivism remains arguably problematic. (shrink)

Unity of science was once a very popular idea among both philosophers and scientists. But it has fallen out of fashion, largely because of its association with reductionism and the challenge from multiple realisation. Pluralism and the disunity of science are the new norm, and higher-level natural kinds and special science laws are considered to have an important role in scientific practice. What kind of reductionism does multiple realisability challenge? What does it take to reduce one phenomenon to another? How (...) do we determine which kinds are natural? What is the ontological basis of unity? In this Element, Tuomas Tahko examines these questions from a contemporary perspective, after a historical overview. The upshot is that there is still value in the idea of a unity of science. We can combine a modest sense of unity with pluralism and give an ontological analysis of unity in terms of natural kind monism. This title is available as Open Access on Cambridge Core. (shrink)

There is a perennial philosophical dream of a certain natural order for the natural kinds. The name of this dream is ‘the hierarchy requirement’. According to this postulate, proper natural kinds form a taxonomy which is both unique and traditional. Here I demonstrate that complex scientific objects exist: objects which generate different systems of scientific classification, produce myriad legitimate alternatives amongst the nonetheless still natural kinds, and make the hierarchical dream impossible to realize, except at absurdly great cost. Philosophical hopes (...) for a certain order in nature cannot be fulfilled. Natural kinds crosscut one another, ubiquitously so, and this crosscutting spells the end of the hierarchical dream. (shrink)

Biochemical kinds such as proteins pose interesting problems for philosophers of science, as they can be studied from the points of view of both biology and chemistry. The relationship between the biological functions of biochemical kinds and the microstructures that they are related to is the key question. This leads us to a more general discussion about ontological reductionism, microstructuralism, and multiple realization at the biology-chemistry interface. On the face of it, biochemical kinds seem to pose a challenge for ontological (...) reductionism and hence motivate a dual theory of chemical and biological kinds, a type of pluralism about natural kinds. But it will be argued that the challenge, which is based on multiple realization, can be addressed. The upshot is that there are reasonable prospects for ontological reductionism about biochemical kinds, which corroborates natural kind monism. (shrink)

This is the first of a pair of papers. It focuses on the development of the most notable phlogistic theories during the period 1766–1791, including the main experiments that their proponents proposed them to interpret. There was a rapid proliferation of late phlogistic theories, particularly from 1784, and the accounts of composition and important implications of the main theories are set out and their issues analysed. Each of them either reached impasses due to internal problems, or included features that made (...) them unacceptable even to other phlogistians. The expositions and analyses of these theories are given in terms of details that were in the literature at the time or otherwise potentially understandable by the participants given contemporary practice. Some relevant methodological aspects of the history of science are discussed, and the secondary literature is briefly surveyed. The second paper deals with the contemporary development of the new chemistry, and with theory comparison and theory choice in the same period. (shrink)

In robustness analysis, hypotheses are supported to the extent that a result proves robust, and a result is robust to the extent that we detect it in diverse ways. But what precise sense of diversity is at work here? In this paper, I show that the formal explications of evidential diversity most often appealed to in work on robustness – which all draw in one way or another on probabilistic independence – fail to shed light on the notion of diversity (...) relevant to robustness analysis. I close by briefly outlining a promising alternative approach inspired by Horwich’s (1982) eliminative account of evidential diversity. (shrink)

Following Kripke and Putnam, the received view of chemical kinds has been a microstructuralist one. To be a microstructuralist about chemical kinds is to think that membership in said kinds is conferred by microstructural properties. Recently, the received microstructuralist view has been elaborated and defended, but it has also been attacked on the basis of complexities, both chemical and ontological. Here, I look at which complexities really challenge the microstructuralist view; at how the view itself might be made more complicated (...) in order to accommodate such challenges; and finally, at what this increasingly complicated picture implies for our standard assessment of chemical kindhood—primarily, for the widespread assumption that chemical kinds in general are more neat and tidy than those messy biological ones. _1_ The Received View _2_ A Taxonomy of Chemical Kinds _3_ Atomic Number _4_ H2O, H3O+, OH−, and More _5_ Complicating the Microstructuralist Picture _6_ Concrete and Other Mixtures _7_ Macromolecules, Especially Proteins _8_ Abandoning Sameness of Elemental Composition _9_ Not So Different after All. (shrink)

How do we refer to chemical substances, and in particular to chemical elements? This question relates to many philosophical questions, including whether or not theories are incommensurable, the extent to which past theories are later discarded, and issues about scientific realism. This chapter considers the first explicit reference to types of colorless air in late-eighteenth-century chemical practice. Reference to a gas by one chemist was generally intended to give others epistemological, methodological, and practical access to the gas. This chapter proposes (...) a causal-descriptive theory of reference for chemical substances. Implications for debates about incommensurability and realism are also briefly noted. (shrink)

Recently, philosophers have come forth with approaches to chemistry based on its actual practice, imparting to it a proper aim and character of its own. These approaches add to the currently growing movement of pluralist philosophies of science. We draw on recent pluralist accounts from chemistry and analyse three notions from modern chemical practice and theory in terms of these accounts, in order to complement the so far more general pluralist approaches with specific evidence. Our survey reveals that the concept (...) of element indicates conceptual pluralisms in chemistry. that electronegativity illustrates methodological pluralism in determining one and the same concept, and that acidity is an instance of plurality hidden behind ‘one notion’. (shrink)

This paper argues that the field of chemistry underwent a significant change of theory in the early twentieth century, when atomic number replaced atomic weight as the principle for ordering and identifying the chemical elements. It is a classic case of a Kuhnian revolution. In the process of addressing anomalies, chemists who were trained to see elements as defined by their atomic weight discovered that their theoretical assumptions were impediments to understanding the chemical world. The only way to normalize the (...) anomalies was to introduce new concepts, and a new conceptual understanding of what it is to be an element. In the process of making these changes, a new scientific lexicon emerged, one that took atomic number to be the defining feature of a chemical element. (shrink)