DiTeresi, Christopher AKing, Kenneth2019-09-122019-09-12https://hdl.handle.net/1920/11599Symmetry inferences in the physical sciences have material warrants; these warrants can be accounted for in terms of scientific practice and conceptual adaptation. This study is a historical epistemology that provides such an account. It covers the emergence and development of symmetry warrants in the crystallographic research programs of the nineteenth century; it also provides evidence and reasoning undermining alternative accounts that characterize symmetry in mathematical rather than material terms. The study suggests that symmetry concepts adapted in order to reduce the number of arbitrary assumptions and parameters otherwise required by crystallographic research programs to account for an expanding range of physical properties that were being measured with ever-greater precision. The use of symmetry reasoning in these programs lessened the dependence of scientific practice on theory and, by doing so, restrained speculative theorizing, established common ground for practitioners with diverse ontological assumptions, and facilitated experimental progress even where theoretical understanding was weak. Further historical research on the development of symmetry reasoning in crystallography and its spread from that field to others will reveal whether there are also material warrants for the continued evolution and transfer of symmetry reasoning. The stakes are high because the use of symmetry inference is pervasive, a priori reasoning about physical symmetries is common but unwarranted, and errors can be costly.enSymmetry inferenceMaterial logicMaterial warrantsConceptual adaptationHistorical epistemiologyCrystallographyThesis