Brian Flanagan, Ph.D. is Associate Professor of Theology at Marymount University in Arlington, Virginia. He pursues research on ecclesiology, ecumenism, and theological method, and is the author of Stumbling in Holiness: Sin and Sanctity in the Church, forthcoming in September 2018 from Liturgical Press, as well as Communion, Diversity, and Salvation: The Contribution of Jean-Marie Tillard to Systematic Ecclesiology (T&T Clark/Continuum, 2011).