Formally, Katherine Sonderegger's The Doctrine of the Holy Trinity: Processions and Persons, the second volume of her Systematic Theology, reflects a classical dogmatic pattern of moving from the topic De Deo uno (the subject of volume 1) to De Deo trino.Footnote ¹ In fact, however, it is her position that any approach to the Christian doctrine of God that sets unity and trinity against one another, as though the latter were in any way a modification or qualification of the former, is deeply mistaken. Rejecting recent theological objections to ‘mere monotheism’, Sonderegger continues in this volume her turn away from the programmatic christocentrism that has dominated Western Christian reflection on God since Schleiermacher. As a result, her argument takes the form of a firm (if always respectful) rejection of the modern tendency to ground the Trinity in the economy in favour of a counter-proposal according to which the doctrine is understood and developed in terms of divine immanence – and thus in sharp distinction from proposals that view trinitarian thinking as augmenting (let alone correcting) the doctrine of God found in the Old Testament.

In line with this approach, Sonderegger supplements her claim that ‘not all is Christology’, which was a leitmotif of volume 1 (see pp. xvii, 322, 331, 363, 417), with the insistence that ‘all is not soteriology’ (pp. 33, 37, 51, 55, 66), as though the Trinity were reducible to the mystery of salvation. Here she contrasts her approach with that exemplified in different ways by Barth and Rahner (and characteristic of the ‘Trinitarian renaissance’ that developed in their wake), according to which it is only by way of the economy that the immanent Trinity is disclosed. To be sure, while she demurs from deriving the Trinity from christology, her doctrine remains dependent on scripture: her contention is simply that the scriptures of Israel are adequate to the purpose. The difference nevertheless is significant: it is not simply that the doctrine of the Trinity cannot be tied to ‘the history of its development in the early church’ (p. xix), but that it is no longer tied to the historicisation of God's life in the incarnation. Because Trinity is simply the mystery of God, it both may and must be understood independently of the economy of salvation.

Of course, there is nothing especially novel about the idea that God is triune independently of the incarnation; but Sonderegger contends that modern theology's tying of the immanent to the economic Trinity on the basis of the ordo cognoscendi has in fact led to a deformed understanding of the ordo essendi, with the result that the priority of the ‘immanent Trinity’ is eclipsed in practice, if not in theory. Noting that beginning with the economy gives priority to the divine persons in a way that leads to unfortunate anthropomorphisms (most egregiously, in doctrines of the ‘social Trinity’), Sonderegger denies that the Trinity is fundamentally about persons at all, arguing instead for the conceptual priority of the divine processions. While she concedes that the two cannot be separated, she nevertheless maintains that proper dogmatic exposition follows the order of ‘a doctrine of the Holy Processions, concluding in the Persons’ (p. xx), on the grounds that, while it is only in the New Testament that the names of the divine persons are given, ‘the Divine Structure’ of processions that is the fundament of God's triunity ‘is taught in sacrificial idiom, in the Law and the Prophets’ (p. xxviii). Only by attending to the Old Testament's witness to the inherent dynamism of the divine life ad intra, she contends, can the spectre of tension between Trinity and unity be definitively dispelled.

As already noted, this turn away from christology does not mean turning from the Bible, but it does entail a rethinking of biblical ontology. Specifically, Sonderegger contends that viewing God as scripture's source suggests that scripture is not best conceived as ‘revelation’ (which suggests that it is primarily a depository of information about God), but rather as a mode of divine presence. Though scripture is a creature (and, indeed, fallible), it has nevertheless ‘been elected out of the nations of the earth … to serve this end, that the whole world should have a creaturely echo, a resonance, a pattern of the Divine Life, in its hands’ (p. 69). By distinguishing biblical knowledge of God from the economy in this way (i.e. by arguing that scripture is not to be read primarily as a record of God's deeds ad extra that thus points back to God only indirectly, but rather as itself a mode of divine presence), she seeks to address the bête noire of much modern theology: the risk that the distinction between what is revealed in history and its eternal divine source will undermine reliable knowledge of God.

The typical modern response to this problem has been to tighten the links between the economic and immanent Trinity which, Sonderegger argues, carries with it the risk of collapsing God into history. By contrast, she contends that the ‘mystery of the Trinity teaches that God is not exhausted … in raw Omnipotence … not simply and utterly Power’, but ‘Plenitude of Being, Fullness … Superabundant, Radiant Life’ (p. 85). In this way, she denies that the basic motivation for trinitarian speech – the ‘problematic’ it addresses – either will or should be found in specifically Christian sources, ‘but rather in the broader, most comprehensive reflection on reality itself’ (p. 115). She thus concludes her case for rethinking a proper approach to the doctrine in chapter 1 with the affirmation that, for the Trinity to arise, there must be ‘an irresoluble disturbance in our account of reality that prompts investigation into a living, differentiated structure of Being Itself’ (p. 115) – and this disturbance, she contends, should not simply be identified with Jesus.

Thus, when in chapter 2 she turns to justifying belief in the Trinity, Sonderegger parts company with the perspective (of which she regards both Aquinas and Barth as exemplars) of the Trinity as a ‘regional’ doctrine peculiar to Christianity. Her alternative is certainly not a straightforward apologetics (a position she associates with Tillich, whose now oft-derided theology she engages with intelligence and sympathy). Instead, she seeks a third way – ‘a doctrine of the Trinity that … commands attention in any proper speculative metaphysic’ (p. 173) – that avoids the both the fideistic risks of regionalism and the prospect of theology's collapse into anthropology that dogs apologetic approaches. She proposes that the structure of reality itself raises questions about being, and that the Trinity addresses them in a way that will be recognisable as such even outside the bounds of Christian confession. In chapter 3 she develops this idea through a chastened doctrine of vestigia Trinitatis. This is not a natural theology, because what she claims emerge in our experience of the world are not the ‘roots of the dogma’ of the Trinity, but rather ‘the echoes, the pattern, and family resemblances of Final Being’ (p. 203). Chiefly, she avers, the Trinity teaches that God in the divine oneness relates to the plural world in plural ways: there is no one divine–world relation, but multiple, reflecting the diversity of the created realities the one God brings into being – and thereby the triune diversity of the divine oneness itself. Borrowing from Giles Emery the idea of redoublement as a means of relating three and one in God (namely, the same infinite reality considered under two irreducible aspects), she suggests that the Trinity can illuminate the problems of the universal and particular that dominate the history of philosophy and, more recently, feminist and critical race theory.

Yet however illuminating such resonances may be for giving Christians confidence in the metaphysical relevance of trinitarian dogma, Sonderegger insists that the only ground of the doctrine is scripture, and she begins unfolding her biblical case for the doctrine in chapter 4, using Isaiah 53 as a means to ‘enact a metaphysical and doctrinal reading of Scripture’ (p. 257) that remains fully respectful of the insights of historical criticism. Thus, she concedes the Isaianic text ‘is manifestly concerned with the earthly life and sorrow of an Israelite, of Israel in the midst of hostile powers, and also … of our Lord Jesus Christ’ (p. 264). Yet she contends that its focus is not primarily God as Saviour (namely, economic), but ‘God as such’ (p. 266), on the grounds that what is being described in the text by way of historical persons are divine processions: the inner life of God.

Her concern here is that dogmatic reasoning not proceed by way of moving from historical reality (e.g. Israel, the servant or Jesus) to the immanent Trinity (namely, the eternal generation of the Son), on the grounds that proper theological order is one in which God gives meaning to the earthly and concrete rather than the earthly providing the content to our knowledge of God. Yet the practical significance of this contrast is difficult to grasp when she argues that Isaiah 53 speaks of ‘a Rupture and a Breaking … in the Divine Life’ (p. 335) that ‘is Procession [namely, the begetting of the Son] in God’ (p. 340). Is not this judgement inevitably based on the earthly reality of the servant (however that figure is to be identified in detail) – and thus of a move in the ordo cognoscendi from the economy to the inner life of God? Sonderegger argues that the upshot of this text is that the ‘Life of God is costly’ (p. 348), and her contention that this cost is seen in the depiction of the servant, as well as the fact that throughout scripture God's ‘ambassadors find rejection and obloquy and anguish their lot’ (p. 349), seems to follow the same move up from economy to eternity to which she objects in Barth and others.

Chapter 5 moves from extended reflection on a single verse in Isaiah to a much larger portion of scripture: the book of Leviticus, which Sonderegger regards as a (if not the) resource for grounding a proper trinitarian theology. The exegetical emphases here are compelling, not least in the form of a sharp reaction against the tendency among Christians to subsume the legal teachings of the Torah to narrative accounts. Sonderegger instead insists that the two be treated as equally important and mutually constitutive in interpreting the biblical witness. In her attempts to show how sacrifice bears witness to the goodness and majesty of God, she wrestles not only with the biblical texts, but also with the critiques of sacrifice made by feminist and womanist theologians. She counters that it cannot be dispensed with, because it ‘is the place where Israel meets the Holy God’ (p. 406) and argues that sacrifice as reflective of God's internal dynamism, such that the ‘Holy Fire of God … is the Old Testament expression of the Trinitarian Processions’ (p. 412), as Self-Offering, Gift received and Gift Offered (p. 418). Once more, the prioritisation of the processions that follows from her exegesis is crucial for Sonderegger as a means of countering any contrastive juxtaposition of the two testaments’ witness to God and, correspondingly of giving proper priority to Israel's confession of God as the dynamic, living One. She is emphatic that if the Christian claim to witness to Israel's God is to be credible, then ‘the Oneness of God must govern all other Christian doctrinal teaching’ (p. 423).

Chapter 6 returns to the metaphysical power of trinitarian doctrine by arguing that it provides conceptual depth to Being – a category that has in the modern period seemed doubtful to many because of its vagueness and generality. In the face of the seeming tension between the particularity and contingency of the biblical narrative on the one hand, and philosophy's focus on the universal and necessary on the other, Sonderegger avers that the Trinity bridges the divide by teaching (in another manifestation of trinitarian redoublement) that God is a ‘Bounded Infinity’ (p. 489). This claim prompts a fascinating review of thinking about infinity that moves through Thomas, Scotus and Descartes, and culminates in Georg Cantor. She reads this history as mapping a shift from viewing infinity as formless negation or mere potential (the ancient view) to a resolutely positive conception (in Cantor's set theory): complete (or bounded), and thus thinkable, while remaining nevertheless inexhaustible. Transfinite sets thus become another vestigium Trinitatis: ‘We do not have parts in the Trinity. … Rather, the Persons, as Perfections of the Divine Processional Life, are simply gathered together as a quasi-set. They are Three, and their distinctiveness, a quasi-ordinal, is complete; however, They mutually indwell One Another’ (p. 512).

The final chapter concludes the argument with the doctrine of the divine persons, understood as the termini of the intradivine processions. Once more, the dogmatic significance of the persons for trinitarian doctrine is clearly circumscribed: they ‘are not the real subject matter of the dogma … and They are even less the reflection of the revealed economy up into the Eternal Godhead’ (p. 519). They function as another redoublement, in that they show that the ‘Heat and Light of the Divine Fire … have Absolute and Intellectual Names’, and so that the processions are ‘not inert forces but Intelligent Agency’ (p. 522). In assessing the traditional Augustinian approach that (again, working from the economy) defines the persons in terms of relations of opposition, Sonderegger notes not only its inevitable drift toward tritheism, but also its tendency to marginalise the Holy Spirit, whose name does not suggest any oppositional relation, which must therefore be found by way of alternative lexical manoeuvres (beginning with Augustine's resort to the dyad of ‘Gift’ and ‘Giver’). She writes, ‘I cannot think that our fealty to this One Lord of Heaven and earth has been properly deepened and straitened by the novelty of focus on Persons in Relation’ (p. 531). Instead, she maintains that the doctrine of the persons should be viewed as the consummation but not the focus of Christian teaching about God: their role is to emphasise the One God's living character, not to be objects of attention in their own right.

Any assessment of this volume must begin with a clear affirmation that it is a brilliant book. The biblical exegesis is masterful and profound, at once conversant with historical-critical questions, deeply sensitive to the human situation to which scripture speaks, and palpably informed by Sonderegger's conviction of God's presence in the text. Likewise, the attempts to show the Trinity's relevance for metaphysics display a command of the Western philosophical tradition that is disarming in its deftness. The range of Sonderegger's interlocutors is immense, and – all the more significantly given the ease with which far too many writers treat theological opponents either dismissively or as betrayers of the gospel – each is engaged with deep respect and appreciation even when cited as an example of an approach to be resisted. Beyond these particular features, moreover, Sonderegger's a theological vision is as comprehensive as it is conceptually bold, informed throughout by deep piety that is at once exuberant in tone and ecumenical in vision. It is hard to think of a more cheerfully confident dogmatics that has appeared since Barth's. Not only does it give powerful witness to the oneness of God, it is also a compelling example of a unitive reading of scripture in the face of the perennial Christian temptation to overbalance on the side of the New Testament. Indeed, not all is christology, nor is all soteriology.

And yet for all the valuable insights and intuitions that mark this text, I remain unpersuaded by its key arguments. Sonderegger is surely right to worry that much modern trinitarianism (and the christocentrism with which it is so closely bound) is marked not only by a tendency toward tritheism, but also by a conflation of the ordo cognoscendi with the ordo essendi that risks collapsing the distinction between God and the world. It is surely an open question, however, whether her own approach does not amount to an overcorrection. For example, when she worries that that ‘the inner life of God has been sharply attenuated, indeed eclipsed by the work of redemption’ (p. 453), one might ask how much attention to God's inner life is theology's business? Without question the idea that the divine life is inert must be avoided, but such views (as Sonderegger herself notes) are arguably more characteristic of certain traditional Reformed theologies than modern ones; and one might (following Karen Kilby) argue that one of the distinct demerits of the late twentieth-century enthusiasm for social trinitarianism is its exhibition of rather too much speculative interest in the inner life of God. Sonderegger's worry that for much modern theology the immanent Trinity serves only as a ‘limit concept’ is an important one, but a certain speculative reticence in this area seems perfectly consistent with Sonderegger's own claim that the upshot of the doctrine of the divine processions is that ‘there exists an act who is God, Utterly Unique, beyond kind and genre’ (p. 454).

In any case, it remains unclear to me that the sorts of corrections Sonderegger rightly calls for can only be obtained by sundering every connection between Trinity and the economy (namely, christology). Perhaps more to the point, however, there seems to me a conflation in her argument between the idea that the Trinity is fully consistent with the picture of God in the Old Testament, and her much stronger claim that the Old Testament teaches the Trinity – to the extent that she finds objectionable any account of the doctrine that would suggest that a non-Christian could not discover it there (p. 25). But the stubborn fact is that no non-Christian ever has discovered it there, making the claim that the ‘ancient Israel's sacrificial cultus … guides and grounds the dogma of the Holy Trinity’ (p. 367) difficult to accept. The idea that Jews might recognise the central theological claims of trinitarian doctrine as addressing familiar concerns under another idiom is attractive – but it does not seem to me to require the much more questionable claim that the dogma is grounded in the Old Testament.

Early in the book, Sonderegger asks whether the Trinity could have been known apart from the incarnation (p. 28), and (as far as I can see) she never quite answers it. I do not see how the answer could be other than ‘No’. For the refusal to ground the doctrine in christology raises the question of why the Old Testament's depiction of the living dynamism of the God of Israel should result just in the confession of Trinity rather than the non-triune Unity of Islamic tawhid or, for that matter, a Duality or a Quaternity. Sonderegger is worried that, if we concede that it is solely under the pressure of the confession of Jesus as Lord that we know God as triune (i.e. only because of the divine decision to refract or project the divine processions into history as the human life of Jesus, lived in relation to the Father and the Spirit), then the novelty of speech that is introduced on our side by that event must also ‘pick out something New’ in God (p. 533). She prefers to see the revelation of the Son and Spirit in the New Testament as a completion of what is taught in the Old Testament rather than ‘the amending of the unfinished’ (p. 536). Yet it is not clear how in this context amendment is different from completion, or why either should be taken to imply that what we are taught of God in the Old Testament are ‘half-truths’ needing ‘correction’ (p. 536). To learn (as we do) that the life of Israel's God is that of a Son who enjoyed glory with the Father before the foundation of the world is not to impugn the truth of what was known before the Son dwelt among us, any more than my learning something new about a person over time necessarily reduces what I knew before to the status of half-truths. When Sonderegger concedes in discussing the vision to the shepherds in Luke 2 that the immanent Trinity ‘is being taught … in the manifestation of the Child of Bethlehem’ (p. 542), she seems to give the game away: no birth in Bethlehem, no doctrine of the Trinity. Would that admission affect Sonderegger's analysis of the logical priority of God's eternal life over the economy? Or her deft recovery of vestigia Trinitatis? I can't see that it would. Indeed, in what seems to me a supreme irony, in Sonderegger's (admirable) desire to avoid methodological throat-clearing, she seems to me rather too taken up with methodological questions, albeit in a negative register, in that her concern to oppose christocentrism causes her to stake out methodological commitments she could leave aside with no loss to her substantive theological vision.