Andrea Woody

Most contemporary chemists consider quantum mechanics to be the foundational theory of their discipline, although few of the calculations that a strict reduction would seem to require have ever been produced. In this essay I discuss contemporary algebraic and diagrammatic representations of molecular systems derived from quantum mechanical models, specifically configuration interaction wavefunctions for ab initio calculations and molecular orbital energy diagrams. My aim is to suggest that recent dissatisfaction with reductive accounts of chemical theory may stem from both the inability of standard accounts of reduction to incorporate the diverse forms of representation found in chemical practice and our philosophical predilection to analyze all connections between theories in terms of logical reduction

This essay explores the connection between representation and explanation in the sciences. I suggest that scientific representation schemes be viewed as pragmatic tools for acquiring the sort of articulated awareness that is the hallmark of nontrivial knowledge. Crystal field theory in chemistry illustrates this perspective. Certain representations achieve the status of being paradigmatically explanatory, thereby shaping models of intelligibility. In turn, these explanatory preferences serve largely to define and differentiate disciplinary communities by implicitly endorsing particular epistemic aims and values. In this way, the pragmatic nature of explanatory discourse effectively grants its intellectual utility

This essay addresses issues concerningexplanation by exploring how explanatorystructures function within contemporarychemistry. Three examples are discussed:explanations of the behavior of gases using theideal gas law, explanations of trends inchemical properties using the periodic table,and explanations of molecular geometry usingdiagrammatic orbital schemes. In each case,the general explanatory structure, rather thanparticular explanations, occupies center stagein the analysis. It is argued that thisquasi-empirical investigation may be morefruitful than previous analyses that attempt toisolate the essential features of individualexplanations. There are two reasons for thisconclusion, each discussed in some detail. First, the traditional analyses rely on highlyprecarious reasoning. Second, empiricallygrounded investigations provide a more naturalconnection to the core aim of analyses ofexplanation, namely to provide a rationale forthe widely expressed preference for explanatorytheories in science.

This dissertation examines how we may meaningfully attribute explanatoriness to theoretical structures and in turn, how such attributions can, and should, influence theory assessment generally. In this context, I argue against "inference to the best explanation" accounts of explanatory power as well as the deflationary "answers to why questions" proposal of van Fraassen. Though my analysis emphases the role of unification in explanation, I demonstrate ways in which Kitcher's particular account is insufficient. The suggested alternative takes explanatory power to be a measure of theory intelligibility; thus, its value resides in making theories easy to probe, communicate, and ultimately modify. ;An underlying goal of the discussion is to demonstrate, even for a small set of examples, that not all components of rational assessment distill down, in one way or another, to evaluations of a theory's empirical adequacy. Instead, the merits of explanatory structures are argued to be forward-looking, meaning that they hold the potential to contribute significantly to theory development either by providing directives for theoretical modification, perhaps indirectly by guiding empirical investigation, or by facilitating various means of inferential error control. ;The dissertation's central case study concerns the development of twentieth century quantum mechanical theories of the chemical bond, provocative territory because of the diversity of models and representations developed for incorporating a computationally challenging, and potentially intractable, fundamental theory into pre-existing chemical theory and practice. Explicit mathematical techniques as well as various graphical, schematic, and diagrammatic models are examined in some detail. Ultimately these theoretical structures serve as the landscape for exploring, in a preliminary fashion, the influence of representational format on inferential capacities generally. Although the connection between representation and explanation is seldom emphasized, this dissertation offers evidence of the high cost of such neglect