Most scholars share the opinion that Luke 10.18 is an authentic saying of Jesus. But by analysing the vision we can see that the saying in Luke 10.18 fits exactly in Lukan theology. In all probability this Jesus saying is written by Luke as an ‘internal heterodiegetic analepsis’ within the temporal frame of the Gospel. Even the positioning in the scene of the return of the disciples, and its genre as a vision can be explained as Lukan. This paper demonstrates that the ‘historische Plausibilitätskriterium’ proposed by Gerd Theißen and Dagmar Winter should begin with a ‘literarisches Differenzkriterium’. That is to say, to establish historical plausibility it must be possible first to show that the saying probably once had a life of its own and does not fit exactly in its present literary context. But the Jesus saying of Luke 10.18 does not fulfil this initial criterion.