Paul Needham

The various conclusions reached in this paper can be drawn together and briefly summarised in the following thesis: It is necessary to use variables ranging over times explicitly in the object language in the logical analysis of temporal reference in English. A discussion of Arthur Prior ideas, which are in direct opposition to those encompassed here, focuses on the principle that the point of view of the speaker dominates all subordinate clauses, which I maintain and Prior rejects. This leads me to oppose the Priorean approach of considering tenses along the lines of propositional modal operators and in particular to criticise the notion of a proposition with variable truth value. My discussion concerns not only tenses, but also dates, and seeks to provide an account of tenses and dates together in a unified framework.

Aristotelian ideas are presented in a favorable light in Duhem's historical works surveying the history of the notion of chemical combination (1902) and the development of mechanics (1903). The importance Duhem was later to ascribe to Aristotelian ideas as reflected in the weight he attached to medieval science is well known. But the Aristotelian influence on his own mature philosophical perspective, and more particularly on his concern for logical coherence and the development of his ontological views, is not generally acknowledged. There are, however, clear pointers in this direction in these two earlier books on the history of science, which are unashamedly written in such a way as to project the author's own view of what is important in the relevant areas. Thermodynamics was the pinnacle of Duhemian science, and its interpretation requires the reinstatement, in Duhem's view, of Aristotelian conceptions which have been unfashionable since the rise of certain ideas with the scientific revolution of the seventeenth century. The present paper is not primarily an exposition of these Aristotelian views of Duhem's, but an attempt to pursue the interpretation of a macroscopic, thermodynamical perspective on chemical substances from an elementary viewpoint in the spirit of Duhem (1902), sometimes being more definite than Duhem seems to be, and occasionally taking issue with him on certain points. Some of his leading ideas will determine the general approach, but views and problems will also be taken from modern textbooks in an attempt to lay down the general lines along which an explicit ontology--in Quine's sense--of macroscopic theory might be developed

Nancy Cartwright has drawn attention to how explanations are actually given in mathematical sciences. She argues that these procedures support an antirealist thesis that fundamental explanatory laws are not true. Moreover, she claims to be be essentially following Duhem's line of thought in developing this thesis. Without wishing to detract from the importance of her observations, it is suggested that they do not necessarily require the antirealist thesis. The antirealist interpretation of Duhem is also disputed. It is argued that Duhemian points, often understood antirealistically, bear a realist construal, and that antirealist interpretations of Duhem typically run into problems of consistency or of reducing his position to absurdity.

An assessment of the similarities and differences between space and time has played an important part in the development of the views of a number of philosophers about time. Examples of statements about time are compared with allegedly corresponding statements about space to give us analogies and disanalogies according to whether the statements have the same or different truth values. But what are the general principles on which such comparisons are based? In particular, according to what criteria are corresponding sentences paired off? Are there any such general criteria? And if so, do they already presuppose a substantial commitment to one or other of the points of view at issue where analogies and disanalogies are discussed? This paper is concerned with two specific proposals for criteria of correspondence, one due to Richard Gale (1968, 1969) and James Garson (1969), which is rejected, and the other tentatively advanced in its place.

From a modern point of view, compounds are contrasted with elements of which they are composed, and the two categories combine to give the category of substances. Mixtures, on the other hand, might be understood to contrast with pure substances (substances in isolation), so that mixtures are quantities of matter containing several substances (be they compounds or uncombined elements) whereas pure substances are understood to be quantities of matter exhausting the material contents of a region of space which contain only one substance, and might be either a compound or an element. But heterogeneous quantities of matter (comprising several phases) might also be understood to be mixtures. Thus, it is common to speak of a mixture of ice, liquid water and water vapour in equilibrium at the triple point of water, although there is only a single substance present. The general concept of mixture as treated by Gibbs’ phase rule is a quantity of matter comprising either several substances or several phases, “or” being used in the inclusive sense. Gibbs’ phase rule is a relatively recent development in the history of the concept of chemical substance, dating from the latter half of the nineteenth century. The concepts and distinctions it presupposes have not always been apparent. I trace some of the important conceptual developments underlying the important distinctions at issue here from Aristotle, who didn’t distinguish either substance and phase, or what are now called compounds and solutions.

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.

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.

Chemistry, the science of substances and their transformations with roots in antiquity, provides as rich a source as any of the claims about what is not directly observable in the light of ideas reflecting both constancy and change. An important distinction in chemistry is that between macroscopic and microscopic realms, mistaken by positivists as a distinction between observable and theoretical and later by certain realists as a distinction between the merely superficial and the deeply theoretical. Recent realist themes about the preservation of the extension of substance predicates typified by “water” and the view that 20th century scientific atomism vindicates earlier philosophical speculations about the corpuscular constitution of matter are unjustified. The relation between quantum and general chemistry is vexed. Despite questioning particular realist theses, however, none of this raises doubts about the basic realist stance that science seeks and sometimes achieves knowledge of a world independent of our thoughts.

Chemistry builds on distinctions of substance, which presupposes that matter can be divided into substances and compared with other matter and itself on different occasions as being of the same substance. Even identifying a quantity of matter as comprising a single substance presupposes the same substance relation, it being a quantity all of whose spatial parts are the same substance. But criteria of purity have been important for isolating substances and investigating their characteristic properties, which can in turn be used for establishing sameness of substance. With the development of chemistry into a theoretical science it became important that such criteria and characteristics should have a systematic theoretical basis. Thermodynamics was, perhaps, the first comprehensive theory to systematically divide the mass of the bodies with which it deals into distinct substances and offer general criteria governing the number of substances present. But the applicability of such macroscopic criteria is restricted to equilibrium conditions on a macroscopic time scale. They can be compared with microscopic conceptions of molecular structure, with which they have been complemented—some would say superseded. Since many substances are not molecular, however, the general formulation of a microscopic sameness of substance criterion remains unclear.

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.

This book is about matter. It involves our ordinary concept of matter in so far as this deals with enduring continuants that stand in contrast to the occurrents or processes in which they are involved, and concerns the macroscopic realm of middle-sized objects of the kind familiar to us on the surface of the earth and their participation in medium term processes. The emphasis will be on what science rather than philosophical intuition tells us about the world, and on chemistry rather than the physics that is more usually encountered in philosophical discussions. It is the everyday science of matter characterised by differences of chemical substance that constitutes individuated macroscopic bodies of geological and biological complexity—the continuous matter of macroscopic theory and described by mass terms. The discussion might be characterised as descriptive metaphysics, being content, to paraphrase Strawson’s use of the term, to describe the structure of our scientific thought about the actual world. The method in the central chapters dealing with the nature of matter will be to pursue key steps in the historical development of scientific thought about chemical substance and related concepts with a view to tracing the emergence of a systematic ontological interpretation. Aristotle’s and the Stoics’ discussions of elements and mixtures, based on a continuous view of matter, bear some resemblance to modern, macroscopic conceptions and therefore have some interest as precursors to modern views as well as being of conceptual interest in their own right. Some of the issues they raised are still reflected in modern discussions, despite the considerable increase in complexity of the subject. Other ideas, such as the intimate connection between what modern science distinguishes as substance and phase, maintained their grip on the understanding of matter until the end of the eighteenth century. These are some of the important aspects of the properties of matter that have been neglected by linguistic concerns that have dominated the recent study of mass terms and which the present study seeks to redress. It will be of interest to see how the bounds of possibility are delimited by the laws governing the appropriate use of concepts refined for the purpose of describing the behaviour of matter. But the concern with modality will not stretch to venturing into the realms of metaphysical possibility governed by philosophical speculation about individual essences and underlying natures. Like many contemporary discussions of material objects, this one relies heavily on mereology. Unlike several such discussions, this one adheres to the classical principles of mereology governing the usual dyadic relations of part, overlapping, etc. and the operations of sum, product and difference. These principles apply to the mereological structure of regions of space, intervals of time, processes and quantities of matter. Material objects that gain and lose matter are not understood to gain and lose parts and don’t call for a modification of the classic dyadic mereological relations to triadic relations with the introduction of a third term referring to time. Rather, a distinction is drawn between quantities of matter, which don’t gain or lose parts over time, and individuals, which are typically constituted of different quantities of matter at different times. The proper treatment of the temporal aspect of the features of material objects is a central issue in this book. The topics falling under this heading are addressed by investigating the conditions governing the application of predicates relating time and other entities. Of particular interest here are relations between quantities of matter and times expressing substance kind, phase and mixture.

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.

Developments in the application of quantum mechanics to the understanding of the chemical bond are traced with a view to examining the evolving conception of the covalent bond. Beginning with the first quantum mechanical resolution of the apparent paradox in Lewis’s conception of a shared electron pair bond by Heitler and London, the ensuing account takes up the challenge molecular orbital theory seemed to pose to the classical conception of the bond. We will see that the threat of delocalisation can be overstated, although it is questionable whether this should be seen as reinstating the issue of the existence of the chemical bond. More salient are some recent developments in a longstanding discussion of how to understand the causal aspects of the bonding interaction—the nature of the force involved in the covalent link—which are taken up in the latter part of the paper.