his essay deals with mental spaces, the underlying cognitive theory behind them, and that theory's broad influence in Cognitive Linguistics, a school of linguistics that identifies knowledge of language with its use and the vast range of cognitive and cultural resources users tap into when constructing meaning. The essay addresses he basic architecture of the mental spaces model, as articulated by Gilles Fauconnier and his students and collaborators, through an exploration of how mental spaces theory evolved into a more generalized theory of meaning construction, capable of modeling a range of phenomena relevant to the study of semantics, pragmatics, and discourse and rhetoric. Semantic and pragmatic phenomena discussed in this study include role versus value readings, referential opacity, depictive reference, presupposition, conditionals, counterfactuals and analogical counterfactuals, and deixis. The essay concludes by applying a mental spaces theory to model meaning construction in written discourse.