Vanessa Seifert

There are many—not just one—periodic laws in chemistry. These laws correspond to nonaccidental regularity relations about physical and chemical properties of (sets of) chemical elements. I support this by showing how these regularity relations can be understood from the perspective of a philosophical analysis of laws. Specifically, I show that these relations instantiate standard features associated with laws; they can be spelled out in terms of two standard accounts of laws; and they can coherently figure in debates about the reality of laws as plausible candidates of ceteris paribus laws.

Presento un argumento que socava la visión estándar de que las sustancias químicas son clases naturales. Este argumento se basa en el examen de las propiedades requeridas para seleccionar a los miembros de estas supuestas clases. En particular, para que una muestra sea identificada —por ejemplo— como miembro de la clase agua, tiene que ser estable en el sentido químico de estabilidad. Sin embargo, la propiedad de estabilidad se determina artificialmente dentro de la práctica química. Esto socava la naturaleza de clase de las sustancias, ya que no satisfacen uno de los dos requisitos clave: que son seleccionadas por (algunas) propiedades naturales y que son categóricamente distintas. Este es un problema específicamente para la interpretación realista natural de las clases. Discuto si hay otras formas de concebir las clases para superarlo.

There are many- not just one- periodic laws in chemistry. These laws correspond to non-accidental regularity relations about physical and chemical properties of (sets of) chemical elements. I support this by showing how these regularity relations can be understood from the perspective of a philosophical analysis of laws. Specifically, I show that these relations instantiate standard features associated with laws; they can be spelled out in terms of two standard accounts of laws; and, they can coherently figure in debates about the reality of laws as plausible candidates of ceteris paribus laws.

The investigation of the relation between chemistry and quantum mechanics includes examining how the two theories each describe an isolated molecule. This paper focuses on one particular characteristic of chemistry’s and quantum mechanics’ descriptions of an isolated molecule; namely on the assumptions made by each description that an isolated molecule is stable and has structure. The paper argues that these assumptions are an idealisation. First, this is because stability and structure are partially determined by factors that concern the context in which a molecule is considered (i.e. thermodynamic conditions, time-range of experiment, environment, etc.). Secondly, the stability and structure of a molecule can only be empirically identified with reference to those factors. This paper examines these assumptions in the context of the philosophical literature on idealisations. This examination is a novel contribution that raises interesting questions about the relation between the two theories, the nature of stability and structure, and the function of these assumptions in the two theories.

Two forms of chemical reaction statements are standardly found in the chemical corpus. First, individual reactions statements describe reactions that occur between specific chemical substances, leading to the production of specific substances. Secondly, general reactions statements describe chemical transformations between groups of substances. Both forms of statements track regularities in nature and are thus warranted to be viewed as representing causal relations. However, a convincing analysis in terms of causation also requires spelling out the metaphysical relation between individual and general reactions. This is because their relation prompts concerns regarding causal priority and causal overdetermination. I present these concerns and address them by arguing that we should view individual and general reactions in the context of the determinate/determinable distinction.

In philosophy, the empirical success of a science is often explained by the fact that it has managed to discover some law(s) of nature. This line of thought has not been thoroughly explored with respect to chemistry. The aim of this paper is to fill this gap by showing how we could think about laws in chemistry. Specifically, it briefly presents how laws of nature are understood in philosophy of science. It then discusses two case studies from chemistry—the periodic table and chemical reactions—and explains how general ideas about law-hood can be applied to these cases. Lastly, it presents research questions and philosophical problems that arise by considering chemistry from the perspective of laws. This analysis illustrates that there is value in thinking about laws in chemistry.

There are many- not just one- periodic laws in chemistry. These laws correspond to non-accidental regularity relations about physical and chemical properties of (sets of) chemical elements. I support this by showing how these regularity relations can be understood from the perspective of a philosophical analysis of laws. Specifically, I show that these relations instantiate standard features associated with laws; they can be spelled out in terms of two standard accounts of laws; and, they can coherently figure in debates about the reality of laws as plausible candidates of ceteris paribus laws.

The place of chemistry in the metaphysics of science may be viewed as peripheral compared to physics and biology. However, a metaphysics of science that disregards chemistry would be incomplete and ill-informed. This Element establishes this claim by showing how key metaphysical issues are informed by drawing on chemistry. Five metaphysical topics are investigated: natural kinds, scientific realism, reduction, laws and causation. These topics are spelled out from the perspective of ten chemical case studies, each of which illuminates the novel ways that metaphysics of science can be informed by chemistry.

I argue that molecules may not have structure in isolation. I support this by investigating how quantum models identify structure for isolated molecules. Specifically, I distinguish between two sets of models: those that identify structure in isolation and those that do not. The former identify structure because they presuppose structural information about the target system via the Born- Oppenheimer approximation. However, it is an idealisation to assume structure in isolation because there is no empirical evidence of this. In fact, whenever structure is empirically examined it is always partially determined by factors that are absent in isolation. Together with the growing empirical evidence that isolated molecules behave in non-classical ways, this shows that the quantum models that do not identify structure are more faithful representations of isolated molecules.

Whether or not quantum physics can account for molecular structure is a matter of considerable controversy. Three of the problems raised in this regard are the problems of molecular structure. We argue that these problems are just special cases of the measurement problem of quantum mechanics: insofar as the measurement problem is solved, the problems of molecular structure are resolved as well. In addition, we explore one consequence of our argument: that claims about the reduction or emergence of molecular structure cannot be settled independently of the choice of a particular resolution to the measurement problem. Specifically, we consider how three standard putative solutions to the measurement problem inform our under- standing of a molecule in isolation, as well as of chemistry’s relation to quantum physics.

This thesis investigates the epistemological and metaphysical relations between chemistry and quantum mechanics. These relations are examined with respect to how chemistry and quantum mechanics each describe a single inert molecule. A review of how these relations are understood in the literature shows that there is a proliferation of positions which focus on how chemistry is separate from quantum mechanics. This proliferation is accompanied by a tendency within the philosophy of chemistry community to connect the legitimacy of the field with the autonomy of chemistry. First, it is argued that this connection should not be made. Secondly, it is argued that chemistry and quantum mechanics are unified in accordance with Harold Kincaid’s model of non-reductive unity because the two theories exhibit particular epistemic and metaphysical interconnections. Thirdly, a metaphysical account is examined which is incompatible with Kincaid’s model of unity; namely strong emergence as understood by Robin Hendry. According to Hendry, the structure of a single inert molecule strongly emerges from its quantum mechanical entities in the sense that there is downward causation. However, Hendry’s defense of this account faces certain problems. Moreover, the putative empirical evidence for his understanding of strong emergence can be explained without invoking strong emergence. This is shown by considering how quantum mechanics assumes an idealized understanding of a molecule’s stability and structure. In the light of the philosophical literature on idealizations, this idealization can be interpreted in two different ways, both of which explain why quantum mechanics describes the structure of a single molecule the way it does, without assuming strong emergence in Hendry’s sense. Each interpretation has philosophical implications regarding the nature of chemical properties, and the relation of chemistry and quantum mechanics. These implications are consistent with Kincaid’s model of unity and thus further support chemistry’s unity with quantum mechanics (as per Kincaid).

How do we refer to chemical substances, and in particular to chemical elements? This question relates to many philosophical questions, including whether or not theories are incommensurable, the extent to which past theories are later discarded, and issues about scientific realism. This chapter considers the first explicit reference to types of colorless air in late-eighteenth-century chemical practice. Reference to a gas by one chemist was generally intended to give others epistemological, methodological, and practical access to the gas. This chapter proposes a causal-descriptive theory of reference for chemical substances. Implications for debates about incommensurability and realism are also briefly noted.

One of the most plausible and widely discussed examples of strong emergence is molecular structure. The only detailed account of it, which has been very influential, is due to Robin Hendry and is formulated in terms of downward causation. This paper explains Hendry’s account of the strong emergence of molecular structure and argues that it is coherent only if one assumes a diachronic reflexive notion of downward causation. However, in the context of this notion of downward causation, the strong emergence of molecular structure faces three challenges that have not been met and which have so far remained unnoticed. First, the putative empirical evidence presented for the strong emergence of molecular structure equally undermines supervenience, which is one of the main tenets of strong emergence. Secondly, it is ambiguous how the assumption of determinate nuclear positions is invoked for the support of strong emergence, as the role of this assumption in Hendry’s argument can be interpreted in more than one way. Lastly, there are understandings of causation which render the postulation of a downward causal relation between a molecule’s structure and its quantum mechanical entities, untenable.

Harold Kincaid in Individualism and the Unity of Science postulates a model of unity-without-reduction in order to accurately describe the relation between individualism and macroeconomics. I present this model and apply it to the description of the relation between chemistry and quantum mechanics. I argue that, when it comes to the description of molecular structure, chemistry and quantum mechanics are unified in Kincaid’s sense. Specifically, the two disciplines contribute to the formation of a unified body of knowledge with respect to molecular structure.