Paul Needham

An exposition of Pierre Duhem’s formulation of the structure of chemical substances as expressed by their formulas is given, presenting it as a development of his essentially Aristotelian view of mixtures. Duhem’s masterly development of the subject displays an eye for logical clarity familiar from his work in thermodynamics but applied here to the extraction of what he regarded as true from the history of chemistry. Though no longer defensible, the account has a conceptual interest in its own right and illuminates a less frequently discussed side of Duhem’s views.

In response to difficulties in understanding the notion of chemical substance at issue in Gibbs’ phase rule, there is a long tradition of reformulating the simple statement of the rule. The leading idea is to rewrite the rule with a term for the number of substances actually present and to introduce additional terms making explicit the various kinds of restrictions which in the original formulation are taken to be incorporated into Gibbs’ notion of the number of independent substances. Although the number of independent substances cannot in general be interpreted as the number of substances actually present, it is not an entirely derivative concept as the authors of the reformulations sometimes seem to presuppose. In particular, it is doubtful whether the number of substances actually present is a clearly delimited concept which can be determined prior to the application of the phase rule. In that case, the phase rule provides a useful source of information for the determination of the number and nature of the substances actually present in a mixture which should be properly reflected in an adequate interpretation of Gibbs’ notion of independent substances. For this purpose, I propose a mereological interpretation of the way independent substances are related to the substances actually present which makes sense of the fact that the former are not uniquely fixed but can be chosen from the latter in several ways

Prima facie, there are two kinds of expression used in English to make reference to time: those involving explicit mention of time and temporal ordering relations, and tenses involving no such explicit reference. Taking as a criterion of adequacy the unification of both these aspects, a systematization is proposed (owing much to Reichenbach) which provides a characterization of tenses. The theory is not based on the notion of a proposition with variable truth value which formed the cornerstone of Arthur Prior’s work. His conception receives a good deal of criticism, ultimately on the ground that relativising to exactly one time is inadequate. We don’t know in advance whether or not no time of perhaps more than one time is relevant, and where this is the case, the analysis cannot be reduced to propositions true at just one time.

The historical development of the understanding of water is traced in the light of the development of the general concept of chemical substance. From the times of the earliest known ancient Greek philosophers, water has played a central role in the conception of the material constitution of the world. But it was Aristotle who developed the most sophisticated understanding of water to have come down to us from the ancients. He viewed it as part of an intricate and systematic theory of chemical substance, which classified water as an element along with earth, fire and air. His view exerted a considerable influence on Arabic and European thinkers throughout the Middle Ages, and wasn’t successfully challenged until the eighteenth century. After Lavoisier, it was recognised that water, though unlike air a single substance and not a mixture, is neither an element nor always liquid. General features of chemical substances, distinguishing elements, compounds and mixtures, were elaborated in a general theory and harmonised with the mechanical features of matter towards the end of the nineteenth century. Finally, the continuous conception of matter underlying the Aristotelian view, which had been unsuccessfully challenged in the seventeenth century, was definitely overturned in the twentieth century, and the intricate microstructure of water was revealed.

Are there events? If so, how are they to be conceived? A line of argument motivating ontological commitment to what I prefer to call processes is presented, drawing primarily on the development of the elementary understanding of thermal processes, but pointing to a broader view by analogical extension. Suggestions are made for an approach to the mereological structure of processes, and some comments are offered of linguistic distinctions sometimes applied to processes and to modal features of events mentioned in the literature.

This article surveys the theory of the part relation (mereology), quantified modal logic, and Kripke and Putnam’s notion of natural kinds. It shows how the former two bear on the macroscopic understanding of the notions of substance and phase, which stands in contrast to the microphysical essentialism of Kripke and Putnam, and can be used to explicate Aristotle’s and the Stoic conceptions of mixture. The article concludes with some comments about the relevance of the issues raised by these ancient theories to modern views of element, compound and mixture.

Despite the importance molecular structure has acquired in 20th century chemistry, more traditional macroscopic notions in terms of a continuous concept of matter continue to play a role in chemical theorising. In the light of the extensive and determined criticism of reductionism in recent philosophy of chemistry, it is of interest to see macroscopic ontology treated autonomously. One aspect of this is developed here, namely the concept of chemical substance. This is characterised by contrast with phases and solutions. The key conception is that of an intensive property, which is defined by appeal to the mereological structure of parts of the entities bearing substance properties.

Classical atoms—“part-less, ontologically irreducible simples” as the conference flyer puts it—are not the atoms of modern chemistry and analogies with the latter can be construed in various ways. They have figured in the historical development of concepts of chemical affinity but without, as Alan Chalmers and I have independently argued, making any significant contribution to empirically justified theories. A purely combinatorial conception of the formation of compounds by juxtaposing atoms is associated with Daltonian atomism. I review the merits of this idea as a solution to problems posed by developments in early nineteenth century chemistry and go on to suggest that subsequent developments in chemistry are as much in agreement with ideas associated with Aristotle as with the ancient atomists, if not more so. The basic issues can be understood without getting involved in detailed chemistry and I hope what I have to say will be of interest to philosophers concerned with the metaphysics of matter but with no special knowledge of chemistry.