Since the problem is primarily a Catholic one, any reconciliation will require that Catholics find a solution through the theological resources of their own tradition. In An Ecumenical Priesthood, Karl Rahner proposes that the nature of the church and the affirmation of the presence of grace among Protestants may open a door to renewal and healing. As canon law validates improperly contracted marriages by examining their fruits, so recognizing the spiritual fruits of Protestant sacraments could allow Catholics to "restipulate" their position on these sacramental acts (and thereby the validity of the ministers who perform them), without revising the Church's original judgment.
Because the book is now nearly fifty years old and deals with internal Catholic questions, it is offered with an introduction to the era and an analysis of the argument, as well as an overview of recent decades of ecumenical discussions.
Karl Rahner, SJ (d. 1984), was among the most influential Catholic theologians of the twentieth century. He taught at the Universities of Innsbruck, Munich, and Münster, and was a major figure at the Second Vatican Council. His voluminous writings include Hearers of the Word, The Trinity, and Foundations of the Christian Faith.
Jakob Karl Rinderknecht is the director of the Pastoral Institute and associate professor of religion at the University of the Incarnate Word in San Antonio, Texas. He is the author of Mapping the Differentiated Consensus of the Joint Declaration, which won the inaugural Harding Meyer Prize in Ecumenism in 2020.