A Jesuite, an exegete of the New Testament and involved in the battle to bring together Jews and Christians between the two World Wars, Father Joseph Bonsirven (1880-1958) is both a strange man and the head figure of the movement, full of richess and harshness, which led some Christians to fight for the establishment of a philo-semitic tradition in the bosom of the Church. Akin to Father Devaux and the Congregation of Notre-Dame de Sion, he plays a prominent part dealing with preaching in Israel and fighting against anti-Semitism, and at the same time with the task of bringing to the light again the Jewish roots of Christianism in the Catholic exegesis. Even if he is undeniably and gratefully acknowledged among those favourably disposed towards a dialogue between Jews and Christians, nevertheless he encounters numerous obstacles, coming mainly from his hierarchy which does not quite understand the meaning of his involvement and repeatedly forbids him to carry on his activity.