This article examines the exchanges between Jean Germain, Bishop of Chalon-sur-Saône, and Jean de Ségovie, Archbishop in title of Caesarea, who withdrew to the priory of Aiton, in the period following the Council of Basel. These exchanges are mainly known to us by what the latter says about them in his correspondence. They show the importance of listening to Jean Germain, for a more refined perception of what the possibility of a dialogue with the Muslims represented in Christian Europe in the mid 15th century.