Robin Hendry

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 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.

Lavoisier defined an element as a chemicalsubstance that cannot be decomposed usingcurrent analytical methods. Mendeleev saw anelement as a substance composed of atoms of thesame atomic weight. These `definitions' doquite different things: Lavoisier'sdistinguishes the elements from the compounds,so that the elements may form the basis of acompositional nomenclature; Mendeleev's offersa criterion of sameness and difference forelemental substances, while Lavoisier's doesnot. In this paper I explore the historical andtheoretical background to each proposal.Lavoisier's and Mendeleev's explicitconceptions of elementhood differed from eachother, and from the official IUPAC definitionof `element' of the 1920s. However, Lavoisierand Mendeleev both subscribed to – andemployed – a deeper notion of a chemicalelement as the component of compound substancesthat (i) can survive chemical change, and (ii)explains the chemical behaviour of itscompounds.

The history of science and the philosophy of science have a long and tangled relationship. On the one hand, philosophical reflection on science can be guided, shaped, and challenged by historical scholarship—a process begun by Thomas Kuhn and continued by successive generations of ‘post-positivist’ historians and philosophers of science. On the other hand, the activity of writing the history of science raises methodological questions concerning, for instance, progress in science, realism and antirealism, and the semantics of scientific theories, questions which are the subject of continued debate in philosophy. Clearly the history and the philosophy of science will continue to challenge each other's research agendas and guiding assumptions.

We argue that the inference from dispositional essentialism about a property (in the broadest sense) to the metaphysical necessity of laws involving it is invalid. Let strict dispositional essentialism be any view according to which any given property’s dispositional character is precisely the same across all possible worlds. Clearly, any version of strict dispositional essentialism rules out worlds with different laws involving that property. Permissive dispositional essentialism is committed to a property’s identity being tied to its dispositional profile or causal role, yet is compatible with moderate interworld variation in a property’s dispositional profile. We provide such a model of dispositional essentialism about a property and metaphysical contingency of the laws involving it.