Abstract In contemporary literature on argumentation, it is well-established that various genres of fiction can be used to present argumentation. For instance, in political satires, authors argue why a certain political situation is undesirable. Similarly, authors of fables argue—by means of animals as characters—that certain behaviour is desirable or unacceptable. Characteristically, authors of fiction create a fictional world in which their narratives take place. This collides with the sincerity conditions of the speech act complex of argumentation: preliminary conditions that should be satisfied for argumentation to be performed correctly. Firstly, these sincerity conditions require the arguer to believe that their standpoint is acceptable. Second, the arguer should believe that the statements they make to justify their standpoint are acceptable and third, the arguer should believe that these statements constitute an acceptable justification of their standpoint. As such, when argumentation meets fiction, the sincerity conditions do not align: how can authors—as arguers—actually believe that their uttered statements are acceptable, if these statements are oftentimes not true? The aim of this paper is to show both how proponents can accept propositions in fiction while still following argumentation’s sincerity conditions.