Millies is a member of several learned societies, including the Association for Political Theory, the Catholic Theological Society of America, and the Society of Christian Ethics. As well, he participates in the International Thomas Merton Society, the Eric Voegelin Society, and he is the secretary for the Edmund Burke Society of America. His book, Joseph Bernardin: Seeking Common Ground (Liturgical Press, 2016), won first place in the biography category for the Catholic Press Association’s 2017 Book Awards. He is a regular contributor to the National Catholic Reporter, and his commentaries have appeared in several periodicals that include America, Commonweal, The Hill, and the Washington Post. In 2020, he was the Pierre Teilhard de Chardin, SJ Visiting Fellow in Catholic Studies at Loyola University Chicago’s Joan and Bill Hank Center for the Catholic Intellectual Heritage.
- Joseph Bernardin: Seeking Common Ground (Liturgical Press, 2016)
- Good Intentions: A History of Catholic Voters’ Road from Roe to Trump (Liturgical Press, 2018)
- A Consistent Ethic of Life: Navigating Catholic Engagement with U.S. Politics (Paulist Press. 2024)
- Cardinal Bernardin’s ‘Consistent Ethic of Life’ still divides Catholics 40 years later (America, 06 December 2023)
- Catholic ‘Groundhog Day’ — American Bishops Can’t See Past Abortion (TheMessenger Opinion, 01 December 2023)
- Pope Francis wants the synod to be a political community—but one based on faith, not interest (America, 25 October 2023)
- Cardinal Bernardin’s Legacy Reminds Us: Catholics Can (and Should) Embrace the Modern World (America, 12 November 2021)
- Joe Biden, the Bishops, & Vatican II: The Battle over the Brand of U.S. Catholicism (America, 16 June 2021)
- “‘The Gift of the People’: A Fresh Look at Our Faithful Citizenship in a Foreboding Moment,” Teilhard de Chardin Lecture, The Joan & Bill Hank Center for the Catholic Intellectual Heritage, Loyola University Chicago (29 October 2020)
- “A De-Escalating Constitutional Alternative to Court-Packing” (The Hill, 5 October 2020)
- “After 50 years, theUS bishops’ focus on abortion has done little to change hearts or minds” America (21 November 2019)
- “Our Dream Soars Higher: Pope Francis’s Call to ‘Civil and Political Love’ in the Crisis of the Twenty-First Century” St. Mark’s College, University of British Columbia (7 November 2019)
- “Ecclesiology is Political” The Berkley Forum, Berkley Center for Religion, Peace & World Affairs (25 September 2019)
- “Illinois Has a Budget! Now What?” Chicago Catholic (6 August 2017)
- “Catholicism and the Common Good.” Chicago Catholic (12 March 2017)
- “He encouraged Catholics to seek ‘common ground.” Catholic New World (13 November 2016)
- “A Sacred Calling.” America (28 March 2016)
- “What Pilate Knew.” America (8 February 2016)
- “Cardinal Bernardin and Cardinal George: Common Ground in Action.” CRUX (23 April 2015)
- “Bringing Liturgy to Life.” America (7 February 2011)