Paul Needham’s book Macroscopic Metaphysics elaborates a systematic metaphysical framework with the aim of analysing, along the lines of Strawson’s (, p. 9; quoted on p. v) ‘descriptive metaphysics’, the ‘actual structure of our thought about the world’. Needham carefully and rigorously develops the structure of the central concepts underlying our thoughts about matter, objects constituted by matter, and processes.
There are several strategies for discovering that structure. One consists in providing a semantic analysis of ordinary language discourse, perhaps in combination with consulting ordinary speakers’ intuitions. Another strategy consists in analysing the conceptual framework implicit in, or presupposed by, scientific discourse. Given that there are many sciences, which are only very partially if at all linked to one another by local and imperfect reductions, the result of the analysis of the metaphysics implicit or presupposed by scientific practice and discourse will depend on the choice of the science or sciences.
Needham’s book makes an original and valuable contribution to the flourishing field of the metaphysics of science by choosing chemistry as the starting point of his enquiry. This choice and its role as the main source of criteria of correctness does not prevent him from considering the appropriateness of the metaphysical categories so elaborated for other sciences—such as quantum physics and biology, but also ecology and geography—for example, when he considers identity conditions for rivers (p. 57). Needham makes it clear at various places throughout that he has no interest in revisionist metaphysical projects such as three-dimensionalism or four-dimensionalism. What Needham calls, in Johnson’s () terminology, ‘continuants’—that is, individuals—are conceived as having three-dimensional identity conditions: they occupy at each time of their existence a definite region of space, but they have no temporal parts, and the moments at which they begin to exist and cease to exist are not part of what determines their identity. On the other hand, events and processes, for which he uses Johnson’s term ‘occurrents’, have temporal parts. The conditions determining their identity are four-dimensional and include both the space they occupy and the temporal intervals at which they occur or during which they develop.
Needham’s metaphysics contains both continuants and occurrents as fundamental ontological categories, contrary to revisionist frameworks, which try to get along with a more parsimonious basis, containing continuants only (reducing what appears superficially as occurrents to continuants relative to times) or occurrents only (reducing what appears superficially as continuants to processes). Needham doesn’t enter into debate about such doctrines because his aim is conservative: his metaphysical system contains all and only those categories as primitive that are required to make sense of chemistry, throughout its history. The general strategy pursued throughout the book is to elaborate a complete structure of metaphysical categories and their relations to each other in such a way as to make sense of the progressive elaboration of the metaphysical concepts underlying chemistry from Antiquity to the present time.
The first chapter lays the ground for the rest of the book. It develops an axiomatic theory of quantities of matter, temporal intervals, and regions of space, building upon classical mereology. A many-sorted language is used in which different variables stand for quantities of matter, temporal intervals, spatial regions, and individuals. Needham develops a rigorous axiomatic theory of these entities, where mereological concepts—such as part, overlap, and separation—are applied to entities of the first three categories but not to individuals. These axioms leave open many issues. There are no axioms stating either the infinite divisibility of quantities of matter—the denial of atomism—or its opposite. They also leave open whether intervals of time and regions of space are infinitely divisible or ultimately discrete. Time comes into play only in the form of intervals, whereas no use is made of the concept of an instant of time. Similarly, Needham’s system contains only extended spatial regions but no points. He makes it clear which questions can and which cannot be addressed within this mereological framework. It would, for example, make no sense within this framework to address van Inwagen’s special composition question, simply because the mereological notion of summation is more abstract than such notions as cohesion or composition.
Chapter 2 develops the concept of occupation, which is the main relation connecting matter to space and time. Needham shows that it is not necessary to introduce boundaries as independent entities. The concept of abutting is shown to do all the work for which boundaries were assumed to be needed, bypassing the puzzles that boundaries raise. Both individuals and quantities of matter obey the principle that each individual and each quantity of matter occupies a region of space at all times. However, individuals do not generally occupy the same region of space as the quantities of matter constituting them. The sea and the atmosphere above it are, for example, continuant individuals. Matter is permanently exchanged between the sea and the atmosphere. In virtue of what Needham calls an ‘accumulation condition’ (p. 36), the air constituting the atmosphere over some finite interval of time is taken to be the sum of all the matter that has been in the atmosphere during some part of that interval or other. So, the matter constituting an individual can occupy a larger region than the individual itself.
Chapter 3 develops the concept of the individual. Needham explores the consequences of different criteria of identity for individuals, without adopting any of them, suggesting that the most plausible choice may depend on the specificity of the individual at issue. In a variant of Theseus’s ship proposed by Peter Simons, a new vessel is constructed from the planks that have been successively discarded from the original ship. On one criterion of identity, this is the same ship; but on another, these are not the same ship, despite the fact that they are constituted, according to the conception of constitution developed earlier, by the same material throughout a given time. Needham shows that puzzles arise from the application of mereological operations to individuals, such as the sum and difference operations, according to which the existence of Descartes would be sufficient for the existence of his left leg, as well as the existence of ‘Descartes-minus’, namely, the result of the difference of Descartes and his left leg. Needham’s system avoids such puzzles by admitting only ‘time-dependent analogues of the mereological relations’ (p. 64) for individuals but not the mereological operations themselves. He also develops modal principles, which yield such plausible results as that an individual isn’t constituted by its matter necessarily. He shows how to express within this framework Kripke’s thesis of the necessity of the origin, without taking a definite stand on whether such a principle is plausible for all individuals.
Chapter 4 explores characteristics of the concepts introduced so far. The property of being a spatial region is both cumulative and distributive; all sums and parts of regions are themselves regions; time is distributive but not cumulative; a binary sum operation can only be applied to connected intervals of time, not to scattered pairs of intervals. Needham shows that no puzzles arise from the possibility that two quantities of matter occupy the same region at the same time.
This issue is related to the analysis of the ancient debate between Aristotle and the Stoics about the nature of mixtures, which is the main theme of Chapter 5. Needham reconstructs Aristotle’s and the Stoics’ conceptions of mixtures, for which he uses Duhem’s term ‘mixts’, so as to mark the fact that no distinction between compounds and solutions had been introduced before the nineteenth century. On Aristotle’s view, a homogeneous substance contains only a single substance, co-occupancy of the same region being taken to be impossible. Aristotle used his theory of four elements in an account of mixing according to which the elements are potentially but not actually present in the mixt. The Stoics held the view, more in line with modern chemistry, that the elements remain present in compounds. However, they didn’t succeed in developing a conception of the elements that could be applied both in isolation and within mixtures.
Chapter 6 introduces the distinction between substance and phase, following its slow elaboration during the eighteenth and nineteenth centuries. Even Lavoisier stuck to the traditional doctrine according to which a substance is essentially tied to a given phase so that, for example, water is necessarily liquid. The distinction between substance and phase is central in Gibb’s phase rule, whose role in modern thermodynamics is explained.
Chapter 7 addresses the question of whether substance predicates such as ‘is water’ are distributive, in the sense that all parts of a quantity of matter that is water are also water, no matter how small the parts are. Needham argues that they are and shows that this is compatible with the molecular structure of water. For times during which the H2O molecules are parts of a macroscopic quantity of water, even the atomic parts of these molecules are parts of water. Against Quine, who has argued that ‘is water’ is not distributive because it doesn’t apply to the atomic constituents of H20 molecules, Needham shows that every macroscopic bulk of water contains a large number of types of molecules, due to the formation of clusters (H20)n and to the spontaneous dissociation of water into hydrogen cations (H+) and hydroxyl anions (OH–). All these molecules are themselves water, so long as they are constitutive of a macroscopic bulk of water. That this is also true for the parts of these molecules is made plausible by the fact that the parts of those molecules are not atoms: the electron configuration of an atom that is part of a molecule is different from the electron configuration of an isolated atom.
Chapter 8 argues for a conception of processes as occurrents: events and processes cannot be reduced, as many philosophers have maintained, in terms of continuants (individuals) and times. Needham analyses the ontological structure of the category of process using the paradigm process of heating, as the concept is employed in chemistry. A process such as heating takes place at a given time between two continuants, that is, quantities of matter. The thesis that processes are ‘causings’ (p. 164) is defended against Davidson’s famous argument from adverbial modification for the existence of events. It is shown that an argument of the same type as Davidson’s but for the existence of processes can be constructed. The analysis of the mereological structure of processes shows that they have both temporal stages and non-temporal parts. An example that illustrates the latter is a process in which a temperature gradient gives rise to a process that has parts consisting of a heating and a flow of electric current (p. 170).
The ninth and last chapter analyses modal features of quantities. Needham shows that there is no straightforward way to overcome the Stoics’ difficulty characterizing the elements that applies both when the elements are isolated and when several of them are present in a mix. The electronic configuration of atoms is not preserved when they are in bonded states, and the atomic number characterizes the nuclei but not the whole atoms making up macroscopic quantities. Needham then develops a new formalism allowing the expression of various modal claims about possible states and processes involving substances such as water. This begins with the claim that water is essentially H2O but that nothing is essentially water, because all parts of a given quantity of matter that is water at one time could also belong to other types of substance, such as H+ and OH–.
The interpretation of the metaphysical framework developed in the book is worth of further exploration. Contrary to what Needham says at the beginning, its aim cannot be to analyse the actual structure of our ordinary or common-sense thought about the world, in the sense of Strawson’s () descriptive metaphysics. To mention just one example, common sense makes no distinction between substances and phases: as Needham explains in Chapter 6, chemistry developed a clear distinction between these concepts only in the nineteenth century. In other words, Needham doesn’t make it completely clear where he stands with respect to the meta-metaphysical question of the status of the conceptual framework elaborated in the book. An instrumental interpretation, according to which metaphysical concepts are tools presupposed and used by science, seems more in line with the spirit of the book than a realist interpretation, according to which the ideal metaphysical theory is not only the most useful (for making sense of science) but also correct. But if the aim of metaphysics is to provide conceptual tools for science, one may ask several questions that the book doesn’t address: Is it conceivable (or compatible with an instrumentalist conception of metaphysics) that there is more than one optimal metaphysical framework that provides a universal tool for all sciences? Is it conceivable that the analysis of the metaphysical framework presupposed by one science, such as chemistry, leads to a different result from the analysis of other sciences, such as physics, geography, or economics? If the answer to the last question is yes, could it be that the metaphysics of chemistry is not complementary but instead incompatible with the metaphysics of some other science? In the light of Needham’s analysis of conceptual changes that have led to modifications of the metaphysical concepts needed to make sense of science, it seems plausible to take the epistemic status of metaphysics to be the same as the status of scientific hypotheses and theories. Both are elaborated and evaluated under the same set of constraints, such as simplicity, consistency, and the compatibility with overall evidence. This seems to entail that the metaphysical framework put forth in the book is as provisional and historical as those scientific hypotheses.
One might also challenge Needham’s refusal to enter debates between rival revisionary theories, such as three- and four-dimensionalism. On an instrumentalist interpretation of metaphysics as a tool, it may seem plausible to leave certain issues open. Maybe one can make sense of chemistry, or of science in general, without deciding whether the concept of a continuant (or individual) can be analysed in terms of occurrents (events and processes), or whether on the contrary the concepts of process and event can be analysed in terms of individuals. But if the aim is to develop a universal tool, in the sense of a unique framework fit for all sciences, and if that tool is assessed with the same criteria as scientific theories, Needham would need to explain why a revisionist framework that reduces, for example, individuals to processes wouldn’t be superior to his own framework, insofar as it fares better with respect to parsimony.
Needham’s book requires some familiarity with logical and mereological formalisms; however, all formulas are also expressed in plain language. Familiarity too with the basic concepts of chemistry certainly makes the analyses of examples more accessible, but it is not absolutely required. And the rigorous elaboration of a formal metaphysical theory does not make the book easy to read. But the reader is rewarded by a thorough analysis of the metaphysics underlying some major episodes in the history of chemistry. Parts of several chapters have been published previously, but all this material is here organised in a well-structured monograph. With its original perspective on the metaphysics of science from the point of view of chemistry rather than physics, the book will be essential reading for philosophers of chemistry with an interest in metaphysics. It will also be a great tool for anyone interested in the metaphysics of science, showing how central the concepts developed here are not only for understanding chemistry but also for making sense of our general knowledge of the objects and processes surrounding us.
Max Kistler Université Paris 1 Panthéon-Sorbonne firstname.lastname@example.org
Johnson, W. E. : Logic, Vol. 1, Cambridge: Cambridge University Press.
Strawson, P. F.  Individuals, London: Methuen.