So much fruit might come from continuing Catholic-Protestant convergence in ethics, Tuininga says.
During the latter part of the 20th century, as I wrote previously, Vatican II reforms and growing concerns about secularism began to draw Protestants and Catholics together.
This convergence has continued into the present among ethicists from both traditions, even as important differences remain.
Convergence among theologians and academics is paralleled in culture and in the public square.
The U.S. Supreme Court's legalization of abortion-on-demand in 1973, in Roe v. Wade, brought Catholic and Protestant clergy together like never before as they struggled to witness to the sanctity of human life.
Similarly, the sexual revolution, with its ever more radical conclusions regarding sex, gender and marriage, has reminded Catholics and Protestants just how much they have in common as heirs of a Christian understanding of the meaning of the body.
The late Pope John Paul II's brilliant reflections on the sanctity of life and the dignity of human sexuality have arguably made him more popular among Protestants than any pope in history.
And yet, the ecumenical convergence has only begun. Profound differences remain.
Most profound, perhaps, is the continued Catholic insistence on a higher, more evangelical ethic for clergy and for Christians who have taken vows, well-known because of its implication that Catholic clergy, monks and nuns may not marry.
Also of practical significance are the absolute Catholic prohibitions of birth control and divorce. Yet even here, as Protestants we have much to learn from our Catholic brothers and sisters.
For example, the Catholic church has long promoted and protected Christian celibacy as an alternative to marriage, in line with the example and teaching of Jesus and the Apostle Paul.
Likewise, the Catholic church has held faithfully to the sanctity of marriage, insisting that divorce is profoundly incompatible with the sacramental meaning of marriage as an analogy for the unity between Christ and the church.
In stark contrast, Protestants have tended to overemphasize marriage as the only ideal life plan for all Christians, while at the same time tolerating and even defending the prevalence of divorce.
Protestants also have much to learn from Catholic social teaching as it pertains to poverty and oppression.
Classic Christian thought taught that God has given the world to human beings in common.
It affirmed the legitimacy of property subject to the requirement that those who have what they need share with those who do not, in order that the poor might receive justice.
This has evolved into the modern Catholic concept of solidarity, which calls Christians to bear the burdens of those who are poor and oppressed.
This "preference for the poor" can be found in a reformer such as John Calvin as well, but it has long since fallen by the wayside among many Protestants.
Protestants would do well to emulate the Catholic conviction that the sanctity of life requires vigorous protection at every stage and in every form, like a "seamless garment" from beginning to end.
Of course, Protestants and Catholics themselves are so divided on ethical and social matters that often conservatives or progressives of each group feel they have more in common with one another than they do with members of their own denominational traditions.
Thus, Protestants who hold to the biblical understanding of marriage might find themselves in greater solidarity with the pope than they do with members of their own tradition, while Catholic academics who support same-sex marriage find themselves arm in arm with many mainline Protestants.
On the other hand, because of its history, breadth and traditional hierarchy, the magisterial Catholic tradition remains far more cohesive and balanced than does much of Protestant ethics.
It is precisely for this reason that so much fruit might come from continuing Catholic-Protestant convergence in ethics.
The more Protestants and Catholics converse with and engage the best of each other's traditions, the more we discover just how rich, broad and consistent is the long tradition of Christian moral and social teaching.
The questions we wrestle with regarding marriage, human dignity and care for the poor are not fundamentally new questions, even though we find ourselves asking them in quite different circumstances.
The gospel of the kingdom and its righteousness remains the same as it did 1,000 and 2,000 years ago, and faithful Protestants and Catholics of all denominations will increasingly find that, as pilgrims on the same journey, serving one Lord with one faith, they will come much nearer to their goal if they walk together than if they walk separately.
Matthew J. Tuininga is assistant professor of moral theology at Calvin Theological Seminary and author of "Calvin's Political Theology and the Public Engagement of the Church: Christ's Two Kingdoms." This article originally appeared in the Fall 2017 edition of Forum, a publication of Calvin Theological Seminary. It is used with permission. His writings also appear on his blog, Christian in America, and you can follow him on Twitter @MJTuininga.
Editor's note: This is the second of a two-part series. Part one is available here.