Diagrammatic carriers and the acceptance of Newton’s optical theory

Abstract

A permissivist framework is developed to include images in the reconstruction of the evidential base and of the theoretical content. The paper uses Newton’s optical theory as a case study to discuss mathematical idealizations and depictions of experiments (‘equidiametric’ and ‘harmonic’ spectral images, ray-paths in drawings of prism-experiments), together with textual correlates of diagrams. Instead of assuming some specific type of theoretical content, focus is on novel traits that are delineable when studying the carriers of a theory. The framework is developed to trace elliptic and ambiguous message design (polysemy), and utilizes variegated acceptance (heterogeneous uptake and polyphony) as an asset. Newton’s resources (novel diagrammatic carriers, mathematical idealizations, and neologisms) allowed for various framing modes and reconstructions, entailing various judgements concerning the theoretical content, the evidence base, and Newton’s use (and/or abuse) of mathematics. Elliptic presentation of the theory’s proof-structure and ambiguities (also pertaining to the function and material setup of the crucial experiment) influenced uptake, contributed to the process of opinion-polarization, and the acceptance/rejection of the theory. The study suggests that the analysed carriers of theoretical content (including visuals) have an argumentative function, and one of their uses is to adjust the burden of proof.