This annotated commentary delineating Michel Pecheux's materialist discourse theory anticipates the formation of a real social science to supersede the metaphysical meanings 'always-already-there' instituted by empirical ideology. Structures of Language presents Pecheux's consequential work in respect of Ferdinand de Saussure's epistemological breakthrough that founded the science of linguistics: the theoretical separation of sound from meaning. Noam Chomsky's generative grammar, John Searle's philosophy of language, B. F. Skinner's indwelling agents, J. L. Austin's speech situations, Jacques Lacan's symbolic order, and other influential linguistic researchers, are cited to explain imaginary semantic systems. The broader implications for structural metaphysics in language use are tacitly conveyed.