As long ago as 1996, Jon Levenson wrote an important article, “The Universal Horizon of Biblical Particularism.” In that piece he reflected on the way in which the Hebrew Bible adjudicated the particularity of Israel and a reach beyond Israel to the nations.
One of the most interesting shifts in Christian theology after the Shoah was in how the adjective Jewish was used. In the patristic era, to call someone’s work Jewish was to insult it: the work was too fleshly or legalistic. Since the Shoah, to call someone’s work Jewish is to praise it as appropriately this-worldly, concerned with the ordinary stuff of life, embodied.
The interface of Jewish and Christian theology has always been vexing. Partly this is because of the intrinsically incommensurate realities of the two faiths. And partly it has been because of Christian interpreters' uncritical practice of supersessionism, which has been combined with political power that is used in controlling and abusive ways.
The scenario might have seemed unlikely: prominent Muslims and Jews from the United States trekking across the Atlantic in mournful, spiritual solidarity to visit two Nazi concentration camps—and doing it together.