Robin Hendry

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.

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 theliteralunderstanding 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 ofnewtheories. The theme of this book is philosophy and technology, and here's the connection:newtheories point out—and explain—newphenomena. 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:newknowledge offeringnewpowers.

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.

In this essay I critically examine the role of entropy of mixing in articulating a macroscopic criterion for the sameness and difference of chemical substances. Consider three cases of mixing in which entropy change occurs: isotopic variants, spin isomers, and populations of atoms in different orthogonal quantum states. Using these cases I argue that entropy of mixing tracks differences between physical states, differences that may or may not correspond to a difference of substance. It does not provide a criterion for the sameness and difference of substance that is appropriate to chemistry.

In this paper I investigate the relationship between vernacular kind terms and specialist scientific vocabularies. Elsewhere I have developed a defence of realism about the chemical elements as natural kinds. This defence depends on identifying the epistemic interests and theoretical conception of the elements that have suffused chemistry since the mid-eighteenth century. Because of this dependence, it is a discipline-specific defence, and would seem to entail important concessions to pluralism about natural kinds. I argue that making this kind of concession does not imply that vernacular kind terms have independent application conditions. Nor does it preclude us saying that chemists, with their particular epistemic interests, have discovered the underlying nature of water, the stuff that is named and thought about in accordance with the practical interests of everyday life. There are limits to pluralism

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.

In this article I sketch G. N. Lewis’s views on chemical bonding and Linus Pauling’s attempt to preserve Lewis’s insights within a quantum‐mechanical theory of the bond. I then set out two broad conceptions of the chemical bond, the structural and the energetic views, which differ on the extent in which they preserve anything like the classical chemical bond in the modern quantum‐mechanical understanding of molecular structure. †To contact the author, please write to: Department of Philosophy, Durham University, 50 Old Elvet, Durham DH1 3HN, UK; e‐mail: [email protected].

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.