In this article, we retrace how sustainability in our study has been communicatively constructed and how it emerged as a dynamic, but also a relatively stable, social fiction. Also, we contribute to methodological reflections on the practical relevance of the (social) imaginary for action. We rely on an empirical study that explores social science-based conversations between and among individuals who talk about the sustainability of their everyday lives. Within daily life people act sustainably to a limited extent, in conflict to the universal claim of sustainability and its normative validity. The respondents see themselves confronted with this well-known dilemma. With the aid of the documentary method, and drawing on our empirical data, we elaborate on the communicative strategies used to meet the difficult combination of sustainability's demands. We focus on patterns of justification, normative-imaginary thought experiments, and rhetorical distancing from the need for action of the present via conjunctive constructions that lean on desirable or undesirable, dystopic or utopic, alternative scenarios. Theoretically, we rely on communicative constructivism and ISER's (1991) literary-anthropological concept of feigning, applying it to the sociology of knowledge. Talk about sustainability serves as an example of how social fictions with a universal claim to validity are communicatively constructed.