The main purpose of this article is, from a semiotic perspective, arguing for the recognizing of a semantic role of the imagination as a necessary condition to our linguistic experience, regarded as an essential feature of the relations of our thought with the world through signification processes ; processes centered in but not reducible to discourse. The text is divided into three parts. The first part presents the traditional position in philosophy and cognitive sciences that had barred until recent times (...) the possibility to investigate the semantic function performed by imagination, mainly due to the anti-psychologist arguments on which it is based. After that, I situate my perspective inside of the recent research panorama in philosophy and cognitive science. The second part presents the semiotic framework on the relation between thought, language, and world, conceived through the concepts of signification processes and sense-conditions. Within this framework, I introduce the concept of linguistic experience, characterizing semantic imagination as one of its sense-conditions. In the third part, several pieces of evidence for corroborating the semantic function of imagination are discussed. These pieces come from the fields of phenomena denoted as diagrammatic thought and counterfactual thought. Diagrammatic thought, briefly discussed, points out the semantic work of imagination in the semi-discursive sign systems constructed in mathematics, logic, and natural science. After defending a widening of the concept of counterfactual thought, and its intrinsic relation with semantic imagination, the role of semantic imagination is briefly discussed in some types of counterfactual thought found in our conceptions of modal concepts, in thought experiments, in apagogical arguments, and in the creative discursive devices. (shrink)