As I underscored and wrote upon how the Being (ousia) of God has been separated from the Persons (hypostases) of God in many medieval and Post Reformed orthodox treatments of the doctrine of God in my personal chapter for our volume one Evangelical Calvinism book, I am happy to see that Cornelius van der Kooi and Gijsbert van den Brink do not follow this type of disjunction in their just released Christian Dogmatics: An Introduction. They would be critical then, as I am, of Katherine Sonderegger’s approach and return back to this more classic rendition of developing a doctrine of God; i.e. by starting with God’s oneness and only later getting to his threeness, as if we could think them apart in any meaningful way as Christ[ians]. Here is what Kooi and Brink have to say about this (in extenso):
We join then this recent turn in asserting that the doctrine of God, with the related treatment of the divine attributes, must be approached from the basis of the doctrine of the divine attributes, must be approached from the basis of the doctrine of the divine Trinity. There there can be no misunderstanding that, speaking from a Christian perspective, God can be thought of only as the Trinity; the Christian church confesses no other God than the Father of Jesus Christ in communion with the Holy Spirit. In that sense the doctrine of the Trinity may be regarded as the Christianized version of the doctrine of God. The church does not worship an anonymous Supreme Being but the God who has made a name for himself in Israel and has gotten a face in Jesus Christ. The divine attributes will also have to be viewed and studied from this perspective, for they do not concern—as has often been suggested—a “universal” divine being, but the triune God. This perspective implies, that right from the start, these attributes must be colored and interpreted by God’s sovereign turn toward us human beings in the history of Israel, Jesus Christ, and the Spirit.
And then in small print, just following, this Kooi and Brink dig further into the way the being of God has been spoken of in abstraction from his persons,
There are numerous examples in history [sic] of studies that first deal at length with the attributes before getting to the doctrine of the Trinity, but the paradigmatic cases are Thomas Aquinas (STh I.2–26 and 27–43) and Schleiermacher (CF, paras. 170–72); yet he judiciously suggests that the doctrine of the Trinity needs to be constructed anew from the oldest sources). The sharp criticism of Karl Rahner (e.g., in Feiner and Löhrer, MS 2:317–97) on how the theological tradition has split apart the tractates De Deo trino and De Deo uno (“On the triune God” and “On the one God”) has become famous. But even Berkhof stays with this tradition. Being disappointed with its classical form, he even decided toward the end of his life to incorporate the doctrine of the Trinity in his doctrine of God at all but to deal with it at the end of his treatment of the doctrine of Christ (CF, paras. 19–23 and 38).
In Calvin’s Institutes the attributes receive little attention, and the doctrine of the Trinity much more. Calvin wanted to stay close to the Bible and practical faith and feared the “idle speculations” that would arise if we isolate various elements of the doctrine of God and make them stand alone. His dictum was, “Hence it is obvious, that in seeking God, the most direct path and fittest method is, not to attempt with presumptuous curiosity to pry into his essence, which is rather to be adored than minutely discussed, but to contemplate him in his works, by which he draws near, becomes familiar, and in a manner communicates himself to us” (Inst. 1.5.9). In his own doctrine of God, therefore, Calvin focused to a large extent on the doctrine of the Trinity, which over time he accepted as fully biblical (1.13; see also Letham 2004, 253, 265, 267–68). In the twentieth century many followed Barth’s example by prioritizing the doctrine of the Trinity over a discussion of the divine attributes (e.g. Genderen and Velema, CRD 143–64 and 164–92; see also 135), but few did so as consistently as Wolfhart Pannenberg (ST 1, chap. 6, as sequel to and colored by chap. 5) and Robert Jenson (ST 1, esp. chaps. 4–9 and 13). See above, chapter 2, for the consequences of mixing the Christian doctrine of God with philosophical ideas about God, which became the target of the prominent critics of religion in the nineteenth century.
To continue to press this let me share a quote I used in my chapter from Thomas Torrance; it is an interesting quote, particularly because while agreeing with Kooi and Brink, in the main, Torrance would appear to disagree with their assessment of Calvin. But the primary reason I am sharing this, for our purposes, is simply to reinforce this type of critique relative to the artificial separating of God’s oneness (‘being’) from his threeness (‘persons’). So Torrance,
in the Scots Confession as in John Knox’s Genevan Liturgy, the doctrine of the Trinity is not added on to a prior conception of God—there is no other content but the Father, the Son, and the Holy Spirit. There was no separation here between the doctrine of the One God (De Deo Uno), and the doctrine of the triune God (De Deo Trino), which had become Roman orthodoxy through the definitive formalisation of Thomas Aquinas. This trinitarian approach was in line with The Little Catechism which Knox brought back from Geneva for the instruction of children in the Kirk. “I believe in God the Father, and in Jesus Christ his Son and in the Holy Spirit, and look for salvation by no other means.” Within this trinitarian frame the centre of focus in the Confession and Catechism alike is upon Jesus Christ himself, for it is only through him and the Gospel he proclaimed that God’s triune reality is made known, but attention is also given to the Holy Spirit. Here once again we have a different starting point from other Reformation Confessions. Whereas they have a believing anthropocentric starting point, such as in the Heidelberg Catechism, this is quite strongly theocentric and trinitarian. Even in Calvin’s Institute, which follows the fourfold pattern in Peter Lombard’s Sentences, the doctrine of the Trinity is given in the thirteenth chapter within the section on the doctrine of God the Creator. Calvin’s Genevan Catechism, however, understandably followed the order of the Apostles’ Creed. The trinitarian teaching in the Scots Confession was by no means limited to the first article for it is found throughout woven into the doctrinal content of subsequent articles.
You might be wondering why this is important, at this point; it has to do with the topic of a recent post of mine on apophatic versus cataphatic theology. When theologies start with the oneness or ‘being of God’ over against the threeness or ‘persons of God’ they are typically taking the apophatic approach to knowing God. They are starting with a discursive rather than concrete way to God; using philosophical categories that conceive of Godness prior to being confronted by that in the definitional reality of His own Self-revelation in Jesus Christ. It potentially gives us a God, the approach under critique in this post, that is abstract and personally removed from his creation; who is not easily understood as a ‘relational’ and dynamic God.
 Cornelius van der Kooi and Gijsbert van den Brink, Christian Dogmatics: An Introduction (Grand Rapids, MI: Wm. B. Eerdmans Publishing Co., 2017), 78-9.
 The small print is a stylistic move used throughout Kooi’s and Brink’s Christian Dogmatics with the purpose of providing more detailed analyses of various loci. It is reminiscent of how Karl Barth used his footnote sections (his “small print”) to accomplish the same thing.
 Kooi and Brink, Christian Dogmatics, 79.
 Thomas F. Torrance, Scottish Theology, 3–4 cited by Bobby Grow, “Analogia Fidei or Analogia Entis?: Either Through Christ or Through Nature,” in Myk Habets and Bobby Grow eds., Evangelical Calvinism: Essays Resourcing the Continuing Reformation of the Church (Eugene, OR: Pickwick Publications, 2012), 110.