So, why don’t Protestants like Natural Law?
The short answer is: there isn’t a short answer.
So starting now, and continuing for who knows how long, I plan to tell the story of the Protestant struggle over natural law, from complete rejection by Karl Barth in the 1930s to the recent hint of renewed interest among Protestant intellectuals. My view is that natural law is a forgotten legacy of the Reformation — one that contemporary Protestants desperately need to rediscover. Along the way, I’ll respond to standard Protestant objections and discuss what limitations the Reformers perceived in natural law.
For much of Christian history, some type of natural-law theory has been used as a bridge to connect the Christian faith and culture, the church and the world. But in recent times, Protestant churches and theologians have rejected natural law as a way of showing their differences with the tradition of Roman Catholic moral theology.
The scope and unity of Roman Catholic social teaching is impressive, but without the recurrent appeal to natural law, it would lack a skeletal structure upon which to build its body of social teaching. Modern Protestant social ethics, by contrast, has no skeletal infrastructure of comparable strength. Unlike Roman Catholic moral theology, which is done in the context of the magisterial (or teaching) authority of the church, Protestant ethics has never had a “supreme court of appeals” to decide what’s licit and illicit. While the Bible is the principal authority in Protestant ethics, the matter of determining “authoritative” moral teaching is complex and subject to personal interpretation. To a fault, I might add.
In his opening address at the first Christian Social Congress in 1891, the Dutch Reformed theologian Abraham Kuyper emphasized the catholicity of natural law in relation to Pope Leo XIII’s new encyclical Rerum Novarum. “We must admit, to our shame,” said Kuyper, “that the Roman Catholics are far ahead of us in their study of the social problem. Indeed, very far ahead. The action of the Roman Catholics should spur us to show more dynamism. The encyclical Rerum novarum of Leo XIII states the principles which are common to all Christians, and which we share with our Roman Catholic compatriots.”
At the heart of Rerum novarum and the recent encyclical Deus caritas est, by Pope Benedict XVI, is an appeal to reason and human nature, but not in a way that denigrates faith or revealed truth. “From God’s standpoint,” insists the pope, “faith liberates reason from its blind spots and therefore helps it to be ever more fully itself. Faith enables reason to do its work more effectively and to see its proper object more clearly.” The Christian Church fulfills its responsibility to form consciences and to promote justice, when, as Benedict insists, social teaching is argued “on the basis of reason and natural law.”
I would like to highlight another passage from Pope Benedict’s 
Despite his many writings, scholarly expertise and long service to the Church as Prefect of Congregation of the Doctrine of the Faith as Cardinal Joseph Ratzinger, there’s still much of an unknown quality surrounding Pope Benedict XVI.
