Ecumenism

One of Berkouwer's crowning achievements was to be delegated by the Council of the GKN to attend the 1957 assemblies of the International Council of Christian Churches, a world fundamentalist body that met in Amsterdam, and the World Council of Churches, the ecumenical body that met that same year in New Delhi, India. In his report back to the GKN, Berkouwer recommended that they join the latter, and they did so, remaining active and becoming one of the first evangelical denominations to enter the mainstream ecumenical movement.

Middle Orthodoxy

Berkouwer displayed in his Studies in Dogmatics an openness that allowed him to develop a friendship and shared views with Hendrikus Berkhof, the leading professor of systematics in the Nederlandse Hervormde Kerk (Dutch Reformed Church from which the Gereformeerde Kerken had split-off in the nineteenth century). The emerging collegial view of these two theologians became known as Middle Orthodoxy, and it aimed in an even more ecumenical direction than the Hervormde/Gereformeerde relationship of the time would suggest.

However, it did not extend so far as to relieve the conscience of the VU theological faculty in regard to their required subscription to the seventeenth-century Canons of Dort, a task which remained to Berkouwer's student and successor in the Chair of Dogmatics, Harry M. Kuitert. (Kuitert, however, went further than his mentor, breaking completely with the Berkouwer and Middle Orthodox tradition and turning publicly to an informal unitarian stance.)

Studies in Dogmatics

Berkouwer wrote a new theological short essay in almost every issue of the GKN weekly Gereformeerde Weekblad, which garnered responses from clergy and laity all over the Netherlands and beyond. A good part of the articles arose from class lectures to his students at VU, where the newspaper letters of response might carry some weight and sometimes occasioned Berkouwer's refinements for his students. The newspaper theological-articles, letters of response, and classroom refinements in turn led to the publication of books over many years under the general series name, Studies in Dogmatics (the last word usually being rendered in English as systematic theology).

The number of titles in the series eventually came to a total of 14 in English, due to the combination of some paired Dutch volumes into a single volume in English. Among key works were The Person of Christ, The Work of Christ, two volumes on Sin, a volume on The Providence of God (which refers to Herman Dooyeweerd's philosophy), General Revelation (again refers to Dooyeweerd), and The Image of God (which especially made the growing movement of philosophers, scientists, and theologians whose thinking was akin to the ideas of Vollenhoven and Dooyeweerd much more comfortable than they had been under Hepp).

Berkouwer's leadership within the denomination to which most of them belonged was strengthened by this openness of the leading GKN theologian, and it contributed to Berkouwer's developing in turn his own position in tandem with that of his friend Berkhof. In an end-of-career work published in English but not Dutch, Two Hundred Years of Theology: A Report of a Personal Journey (Grand Rapids, Michigan: Eerdmans, 1989), Berkhof assessed – along with many other philosophers, philosophical theologians, and systematic theologians – a few leading Gereformeerde historical figures, including Abraham Kuyper and Berkouwer. Berkhof said of the latter, who was in his Studies so leery of speculation, that he suffered from being "not speculative enough."

But he added that since Berkouwer wanted to produce work in systematic theology that was grounded in careful exegesis of the biblical texts for all doctrinal teaching, according to a Reformed tradition of interpretation of the Bible, he mentions few philosophers and interacts sparingly with only one contemporary philosopher, Dooyeweerd, who theologically seems to have had some kinship with Berkouwer and Berkhof's Middle Orthodoxy.