While natural law has played an important role in Christian social ethics from the very beginning, over the centuries it has gone through periods of greater and lesser influence in the Christian church. The sixteenth century, for example, was a period of relatively greater influence, as moral theologians (Protestant and Catholic alike) sought to apply the insights of the Christian moral tradition to pressing issues in foreign affairs, domestic governance, trade, and commerce. The twentieth century, however, can be classified as a period of relatively diminished influence. Philosophically, moral realism sustained vigorous assault from both existentialist and analytic philosophers who denied the existence of transtemporal and transcultural moral goods. Many twentieth-century theologians, heeding the advice of Karl Barth in the celebrated 1934 debate with Emil Brunner, rejected the natural-law tradition in favor of an ethic of divine command.