Robin Findlay Hendry

Elements, Compounds, and Other Chemical Kinds

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.

Two Conceptions of the Chemical Bond

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.

IS THERE DOWNWARD CAUSATION IN CHEMISTRY

Unless the future of chemistry holds some great ontological revision, it seems safe to assume that whenever there is chemical change there is physical change. For instance, on the assumption that an object’s membership of a natural kind is determined by its possession of certain physical properties, there cannot be change in chemical kind membership without change in these kind-constituting physical properties. There is a consensus in recent philosophy of mind that this kind of relationship—known as supervenience—is, however, compatible with a range of views on the ontological relationship between two domains.1 It is, for instance, a commitment both of physicalism—the view that physical laws and facts determine all laws and facts—and of some forms of emergentism, the view that there are autonomous facts associated with the physical systems of higher orders of complexity studied by some of the special sciences. Now chemistry is of multiple interest here. To some of us, it is the central science of matter whose methods, products, and relationship to physics are of interest in themselves, but the relation between chemistry and physics is of wider resonance. As characterized by Oppenheim and Putnam (1958, 407), classical reductionism is explicitly hierarchical and cumulative, and so must be any non-reductive physicalism, insofar as the dependence relation on which it turns is also transitive. Appeal to chemical theories figures large in biochemistry, so establishing the dependence of the chemical on the physical would make it that much easier to establish the physical dependence of the biological (and after that the mental). But that is not all, for in assessing the evidence for the universality of physical law, claims about chemistry must be central (see Hendry 1999). Non-physicalists typically suspect that the universality of physical law is a philosophers’ fiction: a story of conquest that has been extrapolated from a few minor imperialist skirmishes. Since chemistry is right on the border of the empire of physics, this is where the impartial observer might reasonably expect some real applications of physical theory, involving detailed and rigorous treatments of chemical problems, rather than programmatic sketches, promissory notes or claims of reducibility “in principle.”

The Physicists, the Chemists and the Pragmatics of Explanation

In this paper I investigate two views of theoretical explanation in quantum chemistry, advocated by John Clarke Slater and Charles Coulson. Slater argued for quantum‐mechanical rigor, and the primacy of fundamental principles in models of chemical bonding. Coulson emphasized systematic explanatory power within chemistry, and continuity with existing chemical explanations. I relate these views to the epistemic contexts of their disciplines.

Le Poidevin on the Reduction of Chemistry

In this article we critically evaluate Robin Le Poidevins recent attempt to set out an argument for the ontological reduction of chemistry independently of intertheoretic reduction. We argue, firstly, that the argument he envisages applies only to a small part of chemistry, and that there is no obvious way to extend it. We argue, secondly, that the argument cannot establish the reduction of chemistry, properly so called. 1. Introduction2. The scope of the reductionist claim3. The combinatorial argument4. The strength of the ‘reduction’5. Concluding remarks Introduction The scope of the reductionist claim The combinatorial argument The strength of the ‘reduction’ Concluding remarks

Mathematics, Representation and Molecular Structure

The application of quantum-theoretic models to the explanation of chemical structure and bonding is one of the great twentieth-century stories of interaction among disciplines. Some philosophers have found in this interaction both evidential support and historical explanation. The evidential support is for the philosophical doctrine of physicalism, the thesis that everything is, or depends in some way on, the physical. The historical explanation concerns the fall of emergentism, and in particular its doctrines concerning the independence of chemical law. With the emergence of quantum chemistry, the physicalists argue, chemical structure and bonding was explained in terms of physical laws, and the hitherto popular and plausible philosophical view that chemical laws were in some sense sui generis was rendered less popular and plausible, at least among scientifically oriented philosophers.

Reduction, Emergence and Physicalism

Publisher Summary There are two main reasons why the subject matter of physics might be thought ontologically prior to that of chemistry. The first is mereological: properties of wholes depend in some way on the properties of their parts. The second line of thought is that the science of physics is unique in that it aims at full coverage. Since physical laws cover everything, including chemical systems and their parts, if possession of a chemical property confers genuine causal powers, this must be in virtue of some relationship that that chemical property bears to some property that falls under a physical law. Both these considerations are empirical, and are also supported historically by the close interaction between the two disciplines that began in the nineteenth century, when physical methods of investigation like spectroscopy began to be accepted in chemistry. The classical models of intertheoretic reduction are now widely rejected by philosophers, but this chapter considers how well they fit the relationship between physics and chemistry, if only because they are so well understood. The central point is that the failure of the explanatory relationship between physical and chemical theories to fit some model of intertheoretic reduction does not settle the question of whether chemistry is reducible “in principle.” There are many reasons why intertheoretic reductions can fail that are independent of “in principle” reducibility, including mathematical intractability, complexity and conceptual mismatch between different sciences. The chapter also concentrates on the ontological issues, which promise a more direct approach to the question of reducibility in principle.

The Chemical Bond: Structure, Energy and Explanation

The bond is central to modern chemistry’s understanding of the behaviour of matter, figuring in explanations of why chemical reactions happen, what their products are, and how much heat is generated or absorbed in the process. Molecular spectra arise from the vibrations and rotations of bonded groups of atoms. Chemistry provides a wealth of information about the properties and behaviour of individual bonds, and its applications of quantum mechanics offer deep theoretical insights into the structure and bonding of molecules. In this paper I trace the development of classical theories of chemical structure from the nineteenth century to G.N. Lewis. I then develop a structural view of the chemical bond within quantum mechanics, which identifies the chemical bond by its explanatory role within classical structure theory.

Are Realism and Instrumentalism Methodologically Indifferent

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.

Theories and Models: the Interactive View

The semantic view of theories presents theories as families of models. I argue that while the semantic view has helped to make important insights into physical theorising, it tends to obscure the complex nature of theories, which may combine elements from different representational media. I explore this claim in the context of three short case studies.