Materials in this subseries document Heschel's resolute interfaith work, especially building Jewish-Christian relations, inter-religious cooperation and dialogue, and ecumenism. Materials include handwritten notes, correspondence, reports, telegrams, bulletins, press releases, programs, clippings, statements, photographs, and typescripts. Of particular interest are the materials related to the Ecumenical Council during Vatican II which include the proposals put forth to persuade the Catholic Church to condemn deicide, conversion, and anti-Semitism, the Ecumenism Schema, Heschel's correspondence with Cardinal Bea, and personal impressions of Heschel's meetings with the Pope (in 1964 and 1971).