John Langan SJ was a professor whose research interests included: ethics and international affairs, especially applications of just war theory; business ethics; human rights in theory and practice; capital punishment; Catholic social teaching; the place of religion in liberal political thought and the ethical theories of St. Thomas Aquinas and St. Augustine.
He served on the boards of the Bon Secours Health System in Maryland, the Society of Christian Ethics, Theological Studies, and the Georgetown University Press. He was also the chair of the American section of the Council on Christian Approaches to Defense and Disarmament.
His publications included: Developing the Just War Tradition in a Multicultural World, in Peacemaking; Nationalism, Ethnic Conflict, and Religion, in Theological Studies 56; Ethics, Business, and the Economy, in Theological Studies 55; Proportionality, Charity, and the Use of Nuclear Weapons, in The Thomist; Religious Pacifism and and Quietism: A Taxonomic Approach and a Catholic Response, in Pacifism and Quietism in the Abrahamic Faiths. He also edited Catholic Universities in Church and Society and A Moral Vision for America, a collection of the addresses of Cardinal Bernardin on public policy and the consistent ethic of life.