Natural species in chemistry

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We began with chemistry (fifth and sixth lectures). Borrowing certain analyses from the history of chemistry (Meyerson, Duhem, Peirce), we insisted on the relevance of chemical species as a "paradigm" of natural species, before returning to the problem of reductionism, distinguishing between ontological and epistemological reductionism. We clarified the meaning of a "law" in chemistry, recalled what the chemist's "toolbox" consists of, what the periodic system of elements is, and the need to choose the right explanatory model (reductionism, emergentism, occurrence?) if we want to preserve the explanatory autonomy of chemistry [13] and ensure the specificity of its objects and methods [14]. With a few historical reminders, we presented some of the difficulties surrounding the concept of "microstructure" and that of "chemical bonding", which have been the subject of many interpretations (G.N. Lewis' model or "structure", quantum conception of molecular orbitals; criticisms of the structural conception of bonding [15]).

Looking back at recent interpretations of the concept of "molecular structure" and the responses that have been proposed [16], we concluded that the a posteriori essentialist model of Kripke-Putnam could be maintained [17], subject to amendments to essentialism. Assessing our model in the light of chemistry, we felt it passed the test. Not only is chemistry not in conflict with dispositional essentialism, it is in many ways in line with it. 1. The choice of bonding model (Lewis structures or molecular orbitals) allows, depending on use, to respect the distinction between individual and species identities. 2. The natural species uncovered by chemistry have an essence, revealed by the periodic system of elements, provided we understand the chemist's concept of "substance" (Pauling) in a particular sense closer to aliquidism than to the substantialist model. 3. In chemistry, substances include both simples and compounds. And structure must be understood in a dynamic sense: it cannot be thought of independently of chemical bonds and interactions, whatever the bonding model envisaged. The chemist's toolbox is nothing without functional interactions. 4. The proposed model is supported by the image of the chemist's universe, which (thanks to the periodic system of elements) provides satisfactory criteria for distinguishing between the accidental and the essential, while at the same time making possible a dynamic union of inter-theoretical and intra-theoretical bonds, and a non-reductionist consideration of the different levels (molecular, supramolecular, inorganic chemistry, organic chemistry, chemistry of hybrid materials). 5. Applied to chemistry, the model illustrates the (desirable) reconciliation between the "scientific image" and the "manifest image" of the world, by showing the richness and diversity of the models used and the methods that leave plenty of room for imagination and invention, without sacrificing elementary reductionist requirements (the physical-chemical basis, ontologically speaking; the importance of the quantum explanatory model).

At the end of the review, we concluded that the analysis of species in chemistry, the science of classifications par excellence, in no way obliges us to understand them in a purely nominalistic or conceptualist sense. On many occasions, on the contrary, the chemist behaves like a scientific realist, demonstrating through the discovery of hundreds of thousands of species that classifications are not purely and simply stipulated, thus directing us, rather than towards conventionalism, towards a reasoned realism of natural species (Bird versus LaPorte [18]). However, several questions remain unanswered: how is the "pluralism" that emerges from the analysis to be understood, in an epistemological sense or in an ontological sense [19]? Is there or is there not a need for radically distinct orders? Should we rather think of the world in terms of increasing complexity from mineral to organic (Sanchez [20]), of self-organization at all levels, of self-assembly ("letting objects make themselves", Lehn [21])? If examining the natural species of chemistry seems to take us a step closer to realism, can the same be said when we subject the analysis to the test of the biological sciences?

References

[13] Vihalemm R., "The autonomy of chemistry: old and new problems", Foundations of Chemistry, 13, 2011, 97-107.

[14] Needham P.: "Has Daltonian atomism provided chemistry with any explanations?", Philosophy of Science, 71; 2004, 1038-1047; "An Aristotelian theory of chemical substance", Logical Analysis and History of Philosophy, 12, 2009, 149-64; "Microessentialism: What is the argument?", Noûs, 45(1), 2011, 1-21.

[15] Scerri E., "What is an element? What is the periodic table? And what does quantum mechanics contribute to the question?", Foundations of Chemistry, 14(1), 2012, 69-81; Siegfried R., From Elements to Atoms: A History of Chemical Composition, Philadelphia, American Philosophical Society, 2002.

[16] See e.g. Hendry R. F., "Elements, compounds, and other chemical kinds", Philosophy of Science, 2006, 73, 864-75; "Elements" and "Reduction, emergence and physicalism" in Hendry R. F., Needham P. and Woody A. (eds.), Philosophy of Chemistry, 2012, 255-69 and 367-86; VandeWall H., "Why water is not_H2O, and other critiques of essentialist ontology from the philosophy of chemistry", Philosophy of Science, 74(5), 2007, 906-1; van Brakel J., "The Chemistry of Substances and the Philosophy of Mass Terms", Synthese, 69, 1986, 291-324; "Chemistry and Physics: No Need for Metaphysical Glue", Foundations of Chemistry, 12, 2010, 123-36.

[17] On Kripke, see Soames S. "The philosophical significance of the Kripkean necessary aposteriori ", Philosophical Issues, 16, Philosophy of Language, 2006; "Kripke on epistemic and metaphysical possibility: two routes to the necessary a posteriori", in Berger a. (ed.), Saul Kripke, Cambridge, Cambridge UP, 2011, 78-99. On Putnam, see Williams N., "Putnam's Traditional Neo-Essentialism", The Philosophical Quarterly, 61(242), 2011, 151-70.

[18] LaPorte J., "Chemical Kind term reference and the discovery of essence", Noûs, 30, 1996, 112-132; Natural Kinds and Conceptual Change, Cambridge, Cambridge UP, 2004.

[19] Ereshefsky M., 'Eliminative Pluralism', Philosophy of Science, 59; 1992, 671-690; 'Species pluralism and anti-realism', Philosophy of Science, 65(1), 1998, 103-120; Wilkins J., 'How to be a chaste species pluralist-realist', Biology and Philosophy, 18, 2003, 621-638.

[20] Sanchez C., Chimie des matériaux hybrides, Collège de France/Fayard, 2011; Collège de France, 2012, http://books.openedition.org/cdf/493.

[21] Lehn J. M., Chimie des interactions moléculaires (opening lecture), Collège de France, 1980 and closing lecture: Rétrospectives et perspectives (video), 2011, http://www.collegede-france.fr/site/jean-marie-lehn/closing-lecture-2010-06-04.htm.