In 2010, parishioners of St. Nicholas Parish in suburban Chicago met to discuss the diaconate. A parishioner had expressed a desire to become a deacon, so the staff, the parish council, and several parishioners began to study the issue. They hosted four speakers, including Loyola University Chicago theology professor Susan Ross (now president of the Catholic Theological Society of America), who spoke about women as deacons. Before long, St. Nicholas had a committee and a candidate: Lynne Mapes-Riordan, a married mother of two and an attorney.

In January 2011, the parish committee, the pastor, and Mapes-Riordan met with Chicago auxiliary Bishop Francis J. Kane for a preliminary discussion. Three months later the committee wrote a position paper....