Inculturation, the most recent of Catholic evangelizing practices, was developed following the Second Vatican Council in response to the Church’s need for cultural openness. Above all, inculturation is a fusion, a “controlled” syncretisation, offspring of a marriage between Catholicism and the cultures in question. In their missionary territories, priests are the architects of this cultural fusion. In Madagascar’s Bara region, one of them invented an inculturated ritual which is a compromise between a rite of blood-brotherhood (vakirà) and the sacrament of baptism. The present analysis of this catechistic analogy provides the opportunity to re-examine a problematic concept in human sciences and to propose a new approach to syncretism.