What Is a Chemical Element?

Farzad Mahhotian (New York University) - Kant’s rejection of chemistry as a science in his first Critique is well known, as is the fact that he softens that position somewhat in the important 2nd edition of that work. Kant’s work on chemistry late in his life is less familiar, and less definitive. Troubled by a number of unresolved problems including those of substance vs substances (the 2nd Analogy of Experience) and the limits of mechanism (the Metaphysical Foundations of Natural Science), and stimulated by developments in chemistry and physics, Kant outlined a “Transition” project in the 1790s, preserved as part of his Opus Postumum (OP). In an attempt to account for chemical properties and reactions, Kant makes bold claims in OP, including an explicit suspension of the first Critique’s key distinction between regulative and constitutive uses of reason. This suspension occurs in the case of aether, the all-pervasive, pluripotent medium of heat and electricity, and significantly, the medium in which matter moves. Whereas the first Critique had, via transcendental deduction, established space as the a priori “form of outer perception,” the OP’s transcendental deduction explicitly hypostasized space as aether, establishing it as the very ground for the possibility of experience. Suspending the constitutive/regulative distinction impacts Kant’s 2nd antinomy (the “Transcendental Atomistic”) by shifting its focus from apparently mereological issues to ones that lie at the core of his concern with chemistry, namely: questions of elemental identity, integrity and interaction. In the context of the lively debate about what exactly Kant was trying to do in OP, an examination of Ernst Cassirer’s philosophy of science presents fruitful lines of inquiry. Whereas the regulative function of reason loses ground in OP’s hypostasization of space, Cassirer’s reinterpretation of the a priori as purely regulative is central to his philosophy of the growth of knowledge. For Cassirer, the a priori is not prior to experience, they are regulative “logical invariants“ that are “contained as a necessary premise in every valid judgment concerning facts.” Placing ‘regulative’ before ‘invariants’ is meant to indicate that these are 1) not to be understood as axioms that have or will appear at any given point in the history of a science, 2) necessarily plural. So, when Cassirer, following Kant, indicates that chemical elements are regulative ideas, not objects, he means that the concept of chemical element is functional and relational. For Cassirer, chemistry is properly scientific when our understanding of any given element is expressed mathematically as a network of relations expressing connections among empirical observations of chemical elements. Cassirer’s regulative idea of a chemical element implicates the whole network of relations represented by the periodic table—with the proviso that the table as we have it is not the final, or best, or only way of understanding chemical elements. Cassirer’s view of chemistry, as a science whose growth is guided by a relational idea of element, is consistent with recent approaches to mathematical chemistry which have shown that a plurality of periodic relations—and thus periodic tables—can be generated by selectively and systematically analyzing relations among various sets of chemical properties.

Eric Scerri (University of California, Los Angeles) - The dual sense of the term ‘element has attracted a great deal of attention from contemporary philosophers of chemistry. Roughly speaking one sense of the term refers to Lavoisier’s element or simple substances that can be isolated. Secondly, there is a more ancient metaphysical concept of an element as a bearer of properties. The second more abstract sense was revived by Mendeleev while he arrived at his views on chemical periodicity. According to Mendeleev, the latter view is needed to understand the sense in which simple substances exist in their compounds. For example, sodium the well-known light grey and reactive metal does not exist, as such, in the compound sodium chloride. Mendeleev would claim that sodium is still present in the metaphysical sense of the element. My presentation will consist of an examination of some ongoing debated issues over the dual sense of ‘element.’ The following questions will be explored. 1. Are the two senses of element co-extensive or is one contained within the other? 2. What properties, if any, other than atomic number (or atomic weight in Mendeleev’s time) do elements in the more general abstract sense possess? 3. To what extent did Lavoisier abandon the abstract sense of elements while promoting his more positive sense of elements as simple substances? 4. Just how abstractly should Mendeleev’s sense of element be regarded? 5. Should the distinction be regarded macroscopically or microscopically? 6. Does Paneth’s account of the distinction confuse the issue of the abstract sense of element with combined element? 7. To what use did Mendeleev put his sense of element in the course of discovering his version of the periodic table? 8. How is the change from using atomic weight as the ordering principle for the elements, that occurred in the 1920s, connected with the two senses of the concept of element?

Vanessa Seifert (University of Bristol), Geoffrey Blumenthal (University of Bristol), James Ladyman (University of Bristol) - Reference to chemical kinds is often considered in the case of terms such as ‘gold’ and ’water.’ This paper considers the history of reference to types of colourless air, which raise particular issues for the various theories of reference. Many examples of such reference are given from the primary literature. It is shown that in the cases of most of the examples, reference to a gaseous substance started using descriptions of a method of production of the gas and of at least one related distinctive observable property, but without the gas being named. In cases in which initial descriptions were deemed to be vague, more descriptions of distinctive observable properties were added as desired. In most of the examples, such descriptions of a gaseous substance were stated prior to theories about the inner constitution of a gas, or about the dispositions of a gas concerning reactions with other substances, being stated. When names were added, they were generally less definite than the descriptions, which in several cases caused problems. In each of the examples, more than one researcher gave a name to the same gas. While some researchers routinely used terms and substance names belonging to a single type of theory, the examples show other cases in which a researcher adhering to one theory wrote to or concerning the work of a researcher adhering to another theory, using more than one name for a specific substance interchangeably, even though terms within those names formed part of the terminology of different theories. That is for example, the substance name ‘dephlogisticated air’ translated virtually exactly with other names for ‘oxygen’, although ‘dephlogisticated’ did not translate into an antiphlogistic term. This paper argues that in the history of chemistry, reference to a gas by one chemist was intended to give others epistemological, methodological and practical access to it. This paper argues that, generalising from the examples, there were four aspects of the reference that took place in practice: it included or was generally intended to include definite descriptions, which were chosen to refer uniquely or as uniquely as was practicable, to enable a user of the descriptions to know whether they were referring uniquely, and to enable a user of the descriptions to know whether a specific substance was what the descriptions described. Reference to the gas was generally subsequently continuous, and this was knowable in all these ways by researchers due to the initial descriptions used in reference. Such reference underlaid the interchangeable use of names for substances using terms from different theories which is seen in the examples. This paper argues that there are implications of the cases discussed for theories of reference, incommensurability and realism, which deserve further exploration.