Robin Hendry

Philosophers sometimes discuss the “ontological status” of this or that kind of entity. They _should_ be addressing one of the following questions, or the word _ontological_ is being misused: 1. Does X exist? 2. Under what conditions can X exist? 3. Do we have good reasons to think that X exists? All three questions can be asked about elements, and have been asked. Aristotle criticized the atomist account of chemical combination, according to which elements survive in their compounds. Eighteenth-century chemists rejected the Aristotelian view, although tacitly; they simply assumed that an element lives on in its compounds. Nineteenth-century chemists gradually adopted (an adapted form of) atomism, according to which an element can exist wherever its characteristic atoms do. The periodic table also allowed them to ask, of its empty spaces, whether they correspond to real but unknown elements. Priority disputes forced them to consider when there is sufficient evidence for the discovery of new elements. In the 1920s, IUPAC proposed a very thin definition of an element, according to which an element exists wherever its characteristic nuclear charge does. But according to some scientists, it is now challenged by the fleeting existence of some superheavy elements; if a nucleus cannot survive long enough to acquire a stable electronic structure, then it cannot be said to have any chemical properties. How then can it be called a chemical element? In this paper I explore this latest ontological question, in the light of a sufficiently nuanced understanding of earlier ones. I then relate this discussion to a more general question about existence: the Special Composition Question.

In this article I assess the problems and prospects of a microstructural approach to chemical substances. Saul Kripke and Hilary Putnam famously claimed that to be gold is to have atomic number 79 and to be water is to be H2O. I relate the first claim to the concept of element in the history of chemistry, arguing that the reference of element names is determined by atomic number. Compounds are more difficult: water is so complex and heterogeneous at the molecular level that `water is H2O' seems false under some interpretations. I sketch a response to this problem.

Chemical substances such as gold and water provide paradigm examples of natural kinds: They are so central to philosophical discussions on the topic that they often provide the grounds for quite general philosophical claims—in particular that natural kinds must be hierarchical, discrete, and independent of interests. In this chapter I will argue that chemistry in fact undermines such claims. In what follows I will (i) introduce the main kinds of chemical kinds, namely chemical substances and microstructural species; (ii) critically examine some general criteria for being a natural kind in the light of how they apply to chemical kinds; and finally (iii) present two broad theories of how chemical substances are individuated. The primary purpose of this article is to bring scientific detail and sophistication to a topic—natural kinds—which has a long but not always honorable history in philosophy, but chemists can also learn something from these discussions. Chemistry is in the business of making general claims about substances, a fact which is embodied in the periodic table, as well as in the systems of nomenclature and classification published by the International Union of Pure and Applied Chemistry (IUPAC). At several points in the history of their subject, chemists appear to have faced choices about which general categories should appear in these systems. Understanding why these choices were made, and the alternatives rejected, gives us an insight into whether chemistry might have developed differently. This is central to understanding why chemistry looks the way it does today. So, what are the chemical kinds? Chemists study the structure and behavior of substances such as gold, water and benzene, and also of microscopic species such as gold atoms, and water and benzene molecules. They group together higher kinds of substances: groups of elements such as the halogens and alkali metals, broader groups of elements such as the metals, and classes of compounds that share either an elemental component (e.g., chlorides), a microstructural feature (e.g., carboxylic acids), or merely a pattern of chemical reactivity (e.g., acids).

Must potentiality be grounded in actuality? A central issue in the philosophy of chemistryChemistry, going back to Aristotle, is an instance of that very general question: when elements combine, are they actually presentPresent in the compoundCompound substance which results, or are they only potentially present, in the sense that they can be recovered on separationSeparation? Atomism down the ages has been widely understood to endorse the former view, while Aristotle famously defended the latter view, arguing that on the atomist account it is difficult to distinguish genuine chemical combination from mere juxtaposition of the elements. We examine how far, and in what respects, modern chemical theories, enriched by their interaction with physical theories such as quantum mechanics, vindicate atomismAtomism over Aristotle. Our conclusion is that the endorsement is only partial: modern chemistry agrees that elements survive in compounds, but must reject the atomist assumption that, when elementsElement are ‘regenerated’ from a compoundCompound, the portions of matter that result can be identified with those that constituted the elements before combinationCombination.

Mechanisms are the how of chemical reactions. Substances are individuated by their structures at the molecular scale, so a chemical reaction is just the transformation of reagent structures into product structures. Explaining a chemical reaction must therefore involve different hypotheses about how this might happen: proposing, investigating and sometimes eliminating different possible pathways from reagents to products. One distinctive aspect of mechanisms in chemistry is that they are broken down into a few basic kinds of step involving the breaking and making of bonds between atoms. This is necessary for chemical kinetics, the study of how fast reactions happen, and what affects it. It draws on G.N. Lewis’ identification of the chemical bond as involving shared electrons, which from the 1920s achieved the commensuration of chemistry and physics. The breaking or making of a bond just is the transfer of electrons, so a chemical bond on one side of an equation might be balanced on the other side by the appearance of a corresponding quantity of excess charge. A bond is understood to have been exchanged for a pair of electrons. Since reaction mechanisms rely on identities, doesn’t the establishment of a reaction mechanism explain away the chemical phenomena, showing that they are no more than the movement of charges and masses? In one sense yes: these mechanisms seem to involve a conserved-quantity conception of causation. But in another sense no: the ‘lower-level’ entities can do what they do only when embedded in higher-level organisation or structure. There need be no threat of reduction.

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.

Chemistry is the study of the structure and transformation of matter. When Aristotle founded the field in the 4th century BCE, his conceptual grasp of the nature of matter was tailored to accommodate a relatively simple range of observable phenomena. In the 21st century, chemistry has become the largest scientific discipline, producing over half a million publications a year ranging from direct empirical investigations to substantial theoretical work. However, the specialized interest in the conceptual issues arising in chemistry, hereafter Philosophy of Chemistry, is a relatively recent addition to philosophy of science. Philosophy of chemistry has two major parts. In the first, conceptual issues arising within chemistry are carefully articulated and analyzed. Such questions which are internal to chemistry include the nature of substance, atomism, the chemical bond, and synthesis. In the second, traditional topics in philosophy of science such as realism, reduction, explanation, confirmation, and modeling are taken up within the context of chemistry.

The first principle of chemical composition is that elements are actually present in their compounds. It is a golden thread running through the history of compositional thinking in chemistry since before the chemical revolution. Opposed to this principle, which I call Actually Present Elements (APE), is the idea that elements are merely potentially present in their compounds: although not actually present, it is possible to recover them. In this paper I follow that golden thread, and then discuss the status of APE itself: is it true? What arguments were there for it, and when? I argue that APE is a metaphysical principle, albeit at a lower level of generality and abstraction than the term ‘metaphysical’ usually suggests. I critically examine a range of different views on how metaphysical principles might be involved in research programmes in empirical science, and conclude by endorsing Elie Zahar’s view that metaphysical principles such as APE are to be found at the very heart of science. Moreover, they can be recipients of empirical support just like other parts of scientific theory.

Emergence is often described as the idea that the whole is greater than the sum of the parts: interactions among the components of a system lead to distinctive novel properties. It has been invoked to describe the flocking of birds, the phases of matter and human consciousness, along with many other phenomena. Since the nineteenth century, the notion of emergence has been widely applied in philosophy, particularly in contemporary philosophy of mind, philosophy of science and metaphysics. It has more recently become central to scientists' understanding of phenomena across physics, chemistry, complexity and systems theory, biology and the social sciences. The Routledge Handbook of Emergence is an outstanding reference source and exploration of the concept of emergence, and is the first collection of its kind. Thirty-two chapters by an international team of contributors are organised into four parts: Foundations of emergence Emergence and mind Emergence and physics Emergence and the special sciences Within these sections important topics and problems in emergence are explained, including the British Emergentists; weak vs. strong emergence; emergence and downward causation; dependence, complexity and mechanisms; mental causation, consciousness and dualism; quantum mechanics, soft matter and chemistry; and evolution, cognitive science and social sciences. Essential reading for students and researchers in philosophy of mind, philosophy of science and metaphysics, The Routledge Handbook of Emergence will also be of interest to those studying foundational issues in biology, chemistry, physics and psychology.

In this article I argue that structure in chemistry is a creature of abstraction: attending selectively to structural similarities, we neglect differences. There are different ways to abstract, so abstraction is interest dependent. So is structure. First, there are two different and mutually irreducible notions of structure in chemistry: bond structure and geometrical structure. Second, structure is relative to scale : the same substance has different structures at different scales, and relationships of structural sameness and difference vary across the scales. However, these facts have no tendency to undermine structure’s claim to reality, or its metaphysical seriousness.

Arthur Fine and André Kukla have argued that realism and instrumentalism are indifferent with respect to scientific practice. I argue that this claim is ambiguous. One interpretation is that for any practice, the fact that that practice yields predictively successful theories is evidentially indifferent between scientific realism and instrumentalism. On the second construal, the claim is that for any practice, adoption of that practice by a scientist is indifferent between their being a realist or instrumentalist. I argue that there are no good arguments for the indifference claim under the second interpretation, and good reasons to think that it is false.

In this paper I examine the relationship between historians, philosophers and sociologists of science, and indeed scientists themselves. I argue that they co-habit a shared intellectual territory ; and they should be able to do so peacefully, and with mutual respect, even if they disagree radically about how to describe the methods and results of science. I then go on to explore some of the challenges to mutually respectful cohabitation between history, philosophy and sociology of science. I conclude by identifying a familiar kind of project in the philosophy of science which seeks to explore the worldview of a particular scientific discipline, and argue that it too has a right to explore the shared territory even though some historians and sociologists may find it methodologically suspect.

Let strict physicalism be any philosophical account of the ontological relationship between the subject matter of physics and other disciplines that is committed to the causal completeness of the physical. In so far as its status is seriously considered by strict physicalists, completeness is usually taken to be established by appeal to the explanatory interaction between physics and other disciplines. This chapter challenges this view, formulating an emergentist position committed to a non‐trivial form of downward causation, and so the falsity of completeness. It is argued that the explanatory interaction between quantum mechanics and chemistry supports this emergentist position at least as well as it does strict physicalism.

For as long as realists and instrumentalists have disagreed, partisans of both sides have pointed in argument to the actions and sayings of scientists. Realists in particular have often drawn comfort from the literal understanding given even to very theoretical propositions by many of those who are paid to deploy them. The scientists' realism, according to the realist, is not an idle commitment: a literal understanding of past and present theories and concepts underwrites their employment in the construction of new theories. The theme of this book is philosophy and technology, and here's the connection: new theories point out—and explain—new phenomena. So realism, claim the realists, is at the heart of science's achievement of what Bacon, that early philosopher of technology, identified as science's aim: new knowledge offering new powers.