It is argued that the key concepts of quantum theory—Planck’s quantum proposal, de Broglie’s wave–particle dualism and Schrödinger’s wave function idea—are neither incontestable nor integrated seamlessly into the fabric of quantum theory. In fact, it is doubtful whether classical wave treatments can serve as the basis for analysing (purported) matter waves at all. Also, an element of circular reasoning apparently surrounds the wave function concept, as the Hamiltonian-based Schrödinger equation is constrained to lead to the discrete solutions that represent quantization. These ambiguities appear particularly damning against the backdrop of the dubious Rayleigh–Jeans–Planck analysis of black body radiation, and the discredited evidence for the wave theory of radiation (based on purported diffraction phenomena). These considerations raise intriguing questions about the role of mathematical modelling in the study of natural phenomena (not to mention certain pedagogical quandaries). Thus, quantum theory—cloaked though it is in forbidding mathematical rigor—must submit to a dispassionate analysis of its extent and compass, particularly in view of its ostensible subversion of common-sense notions of reality.