Should the dissimilarity between Jesus and early Christianity or between Jesus and Judaism be the central criterion for identifying the historical Jesus? The authors argue that the criterion of dissimilarity does not do justice to the single most important result of more than two hundred years of Jesus research - which is that the historical Jesus belongs to both Judaism and Christianity. They propose a criterion of historical plausibility whereby historical phenomena under question can be considered authentic so long as they can plausibly be understood in their Jewish context and facilitate a plausible explanation for their effect on Christian history.