2.1 Theology and economy

The terminology and concept of the immanent Trinity and economic Trinity is a result of historical developments across the Christian tradition. The earliest relevant terminology is that of ‘theology’ (theologia) and ‘economy’ (oikonomia). Theology in its basic sense refers to speech about God. Though the common use of ‘economy’ pertained to the running of household affairs and other mundane meanings, it came to be attached to the works wrought by God within history. The economy is God’s ordination of his plan for creation before the ages and its execution through the various acts that bring creatures forth and reconcile them so as to bring them to fulfillment (Eph 1:9–12, 3:9; 1 Tim 1:4). God is the eternal agent; the economy is the course of the works wrought by God as its agent.

Patristic thinkers take up and elaborate this distinction, from the earliest theologians such as Irenaeus and Theophilus of Antioch (Studer 1993: ch. 3, 5). These terms preserve proper speech about God and enable rational discourse about how God works in ways accommodating to the spatio-temporal world of creation. Thus, in a more developed form, Augustine of Hippo refers to God ‘unfolding his plan of salvation in a manner suited to the times’ (The Trinity III.22; Augustine of Hippo 2012: 142) to explain the variety of dispensations of his appearances and works. With this distinction, Hilary of Poitiers can explain the apparent ignorance of the omniscient God in various episodes of scripture on the basis of a temporal accommodation to divine and human action (The Trinity IX.62–71; Hilary of Poitiers 2002). The distinction is made between God (theology) and the contingent forms of some of his works (economy) like the human nature of Jesus, emphasizing the asymmetric character of this relation. God does these works, but God does not need to do them in order to be who he is; the possibility of the economy rests upon God’s utter perfection.

Though not strictly the province of the development of trinitarian doctrine, ‘theology’ and ‘economy’ are entangled with trinitarian concerns because of the centrality of God’s working in the Son and Spirit in their earthly manifestations and works. For example: in what degree does the economy manifest who God is in himself? Is the economic appearance of God rooted in God himself? Such questions are at the heart of early trinitarian controversies that led to the decisions of the First Council of Nicaea and the First Council of Constantinople and their surrounding theological debates. One case that is salient to the later discussion of immanent and economic Trinity concerned a form of Monarchianism that later bore the name Sabellianism (after its apparent chief formulator) and modalism (a term given by the church historian Adolf von Harnack), which was espoused by such figures as Praxeas, Sabellius, and Marcellus of Ancyra. Put in overly crude terms, this position proposed that there is only one substance and one person in God; the appearances of the Father, Son, and Spirit are merely manifestations of the one God and Father who assumes different forms or modalities in the progression of the economy. The three distinct manifestations of God in the economy are not really distinctions in God; the linkage between theology and economy is rather looser on this understanding. Apologists, in formulating early Christian doctrine on the Trinity in such forms as Logos doctrine, pressed the case against such ideas by asserting that there is a real distinction of persons in God who wholly share the one substance or nature of God. This can be seen especially in Tertullian’s Against Praxeas (Adversus Praxeam) and the later works of Lactantius and Novatian (Ayres 2004: 62–84; Osborn 1997: 116–143; Studer 1993: 109–110, 140–141).

An extreme remotion of theology and economy, as in Sabellianism/modalism, runs into problems when confronted by scriptural passages such as the high priestly prayer of John 14 in which there is an address of Jesus as the Son to the Father. The problem may be put with some simplicity: how truly ought one regard the manifestation of God as Son and Spirit in history, as attested in scripture, as indicative of who God is in himself? The stakes are greater than one proof text or other of scripture; rather, what is at issue is the theological logic that makes the contents and realities witnessed therein coherent. For example, is the coming into the world of the Son who proclaims his unity with God as his Father coherent if difference is mere appearance, or if his origin is not rooted in an eternal relation of origin? While not a priority of the conciliar debates and creeds, the decisions of the councils of Nicaea I and Constantinople I are indicative of a broad agreement that there must, for example, be a rooting of the temporal appearance of one who is Son of the Father in an eternal begetting of the Son of the Father in the unity of the divine essence (e.g. Studer 1993: 158–159). Yet there was no firm rule for the tightness of this relationship, which gave rise to a variety of possible developments in later theology in both Eastern and Western forms. Despite the lack of conciliar declaration, it was a consistent theme in trinitarian doctrine as it developed in uneven and uniquely contextual ways, from Irenaeus of Lyons to the Latin apologists to the Nicene fathers, even becoming central to the development of christological dogma (Studer 1993: 62–63, 70–75, 113–114; Behr 2004: 212–213, 349–350; see also Conciliar Christology).

2.2 Essence and energies

Another important conceptual distinction is that of the divine essence or substance (ousia) and divine energies (energeiai). While the term for energy had some use in the biblical corpus, it was not of the sort that is important to the sophisticated theological distinction that is in view. The fundamental biblical notion that is important is the invisibility or inaccessibility of God (1 Tim 1:17) who nevertheless makes himself known and available to his creatures (John 1:18; Col 1:15). This distinction developed particularly among the Cappadocian fathers (Basil of Caesarea, Gregory of Nazianzus) alongside other affirmations in the development of trinitarian theology, such as simplicity and indivisibility. The idea is that the divine essence is utterly incomprehensible on the part of human experience; however, God has made himself known to creatures in some way. The essence-energies distinction explains the ‘in some way’ of the statement: the divine essence, what God is, is hidden and above human comprehension; the operations or energies of God that are uncreated and of his life make God known to creatures and it is in these that creatures participate. Because these energies/operations exist in and through the trinitarian relations, humans can know of the persons and participate in their relations, but the one essence remains a mystery. The trinitarian operations are eternal and yet these impinge on the reality of creation and draw creatures into this eternal fellowship. These concepts were augmented and developed later by Maximus the Confessor and Gregory Palamas (see Divine Energies).

For various reasons, this terminology exercises limited influence in the Latin West. Both for linguistic reasons in Latin terms, and for theological reasons, particularly after Augustine of Hippo, Western theology accepts the majesty and incomprehensibility of God while also being reluctant to accept that the essence is hidden in the way asserted by (mostly Greek-speaking) Eastern theology. Views on the degree of knowledge available to humans may vary, but Latin theologians tend to accept that the persons and their operations are indicative in some way of the divine essence in its threefold character, even if humans cannot fully comprehend the divine essence. In the East, for linguistic and theological reasons, the essence-energies distinction endures up to the present and has a distinctive apophatic stress. This conceptual terrain, though a common heritage of the Church, was eclipsed in Western trinitarian theology under the influence of Augustine of Hippo, who exercised rather negligible influence in Eastern Christianity. Thus Western trinitarian theology proves difficult to map in relation to Eastern Orthodox trinitarian theology, including the fundamental concepts in Western theology such as processions and missions and the immanent Trinity and the economic Trinity, as opposed to the essence-energies distinction of the East.

2.3 Eternal processions and temporal missions

In the Latin West, a different terminology affixed itself to the consideration of God in himself and God in his works in the economy in trinitarian theology. This is the idea of eternal processions (processiones) and temporal missions or sendings (missiones). The processions are the trinitarian relations of Father, Son, and Spirit in which the Father eternally generates or begets the Son and, with the Son, eternally spirates (breathes out) the Spirit. The missions are the temporal effects in creation that indicate or bespeak the presence and working of the divine persons sent into the world as aimed at particular ends in the creation, such as the incarnation or the sending of the Spirit upon the church (Summa Theologiae [ST] I.27–28, I.43.1; Aquinas 2006).

The origin of this idea can be seen in the biblical witness. God sends the Son to take up human flesh and thereby to reconcile, redeem, and perfect humanity (Gal 4:4–5; 1 Tim 3:16; 1 John 4:2). Likewise, the Spirit is sent upon the church and is shed upon the hearts of believers (John 14:26; Acts 2; Rom 5:5). Within the divine missions, there are invisible and visible aspects to missions that are interrelated with each other depending on the particular, personal mission and the work being wrought by God for creatures (Vidu 2021: 6–7).

Augustine’s theology, in many matters, is decisive for the Western church. For Augustine, the character of the mission is as a repetition of and indicator of the eternal relation that it manifests for creatures and for their benefit. So, for instance, the Son is

not sent in virtue of some disparity of power or substance or anything in him that was not equal to the Father, but in virtue of the Son being from the Father, not the Father being from the Son. (The Trinity IV.27; Augustine of Hippo 2012: 180)

The mission of the Son in being sent to be born in human flesh repeats his being begotten of the Father. There is an intrinsic connection between the two, but the relationship is derivative and non-reversible: ‘Just as the Father, then, begot and the Son was begotten, so the Father sent and the Son was sent’ (The Trinity IV.29; Augustine of Hippo 2012: 181).

Thomas Aquinas expands Augustine’s theology of missions. The mission elevates the created element, such as human nature in the incarnation, to a mode appropriate to its origin in the eternal procession by grace, and missions depend upon the processions that ground them (ST I.43.2, I.43.3.3; Aquinas 2006). This being the case, one might expect Aquinas to draw the missions and processions into quite close relationship. Yet, when he comes to the topic of the incarnation, Aquinas merely affirms that it is more fitting for the Son because of his status as the one begotten (ST III.3.8). Yet Aquinas also affirms that the Father or the Spirit could just as well have become incarnate (ST III.3.5.c). Some of this is indicative of his metaphysics of the divine substance. It is also bound up in his consideration of the fittingness of the incarnation, that is, the contingency of the created effect of the mission (ST III.1). This raises the question of whether Aquinas’ teaching creates a gap between procession and mission that weakens their intrinsic connection; is the relation of missions to processions one of necessity or fittingness? The answer to this question implicates not only the identity of Christ and the Spirit in their sendings but also the nature of the God that is revealed to humans to know and love.

2.4 Immanent Trinity and economic Trinity

The concept of the ‘immanent Trinity’ (alternatively called the ‘ontological Trinity’) and the ‘economic Trinity’ is the result both of the distinctions of the tradition and of the unique pressures exerted by modernity. The terms ‘immanent Trinity’ and ‘economic Trinity’ themselves are modifications of the early distinction of theology and economy, in that they refer to trinitarian persons and their relations immanently in God’s being (immanent Trinity) and these persons and relations as manifested in the history of salvation (economic Trinity). Important here is the context of Enlightenment criticism of ecclesial dogmas (especially the Trinity), scriptural reliability, and the problem of epistemic certainty concerning God, which is not merely an intellectual problem for believers but also an existential one. Within this context, theologians turned to the theological past for terms and concepts that could aid in defending traditional trinitarian dogma against the various opposing ideas that were rather repetitive of their earlier, heretical forms.

The initial development of the concept of an immanent Trinity and an economic Trinity appears to be the work of a marginal figure of the eighteenth century, Johann August Urlsperger (Pannenberg 1991: 271). Bestowing the terminology that endures to the present, Urlsperger queries whether an economic Trinity is possible apart from a prior, absolute Trinity in God’s being. He defends an intrinsic link and logic between God’s manifestation in the world and his absolute being. If threeness of persons is demonstrated in God’s appearance in the divine economy, then this must be grounded in a fundamental threeness in God’s inner life. However, Urlsperger concedes to Enlightenment critics of trinitarian dogma that God’s revelatory appearance as Father, Son, and Spirit, with their seeming hierarchy, is part of the economy and not reflective of the necessary equality of the threeness in God’s inner being. So the incarnation of the Son, who is nevertheless one with the Father from whom he is sent forth, is indicative of a real distinction in God but not a relation of paternity and filiation. Urlsperger’s argument serves to defend a doctrine of God as Trinity while distancing God from the personal terms and relations such as paternity and filiation as a product of temporal and creaturely appearance (Stolina 2008). Behind the more personal terms of economic threeness is a rather amorphous and vague immanent threeness in the divine being. In view of the later discussion of the close identity of the immanent Trinity and economic Trinity, the origin of this prevailing discourse of modern trinitarian theology in Urlsperger is ironic.

After Urlsperger’s work, the concept and terminology passed into wider use in systematic theology and the history of doctrine. By the latter half of the nineteenth century, this was the dominant terminology in the Western Church beyond the German context, as can be seen by French Roman Catholic theologians identifying the missions with the economic Trinity as a conceptual apparatus for historical theology (Barnes 1995). This latter fact is indicative of a key point – the concept of immanent Trinity and economic Trinity often retains use of previous conceptual terrain such as processions and missions. Though the terminology was carried forward in subsequent discussion of the doctrine of the Trinity, Urlsperger’s gulf between the meaning of the economic Trinity and that of the immanent Trinity was disfavoured as theologians pressed the crucial aspect of Urlsperger’s thesis in the logical rooting of the economic Trinity in the immanent Trinity (Stolina 2008). As with the discussion of processions and missions, there is a lurking issue of the veracity of God’s self-demonstration in the economy in tension with the acknowledgement that the temporal sequence and order is inappropriate to speech about God in himself. Therefore, the immanent Trinity and economic Trinity came to be terms referring to the two aspects of the Trinity based on the reference point taken, with the economic Trinity being the self-revelation in the world of the immanent Trinity. Thus one can speak of the immanent and economic Trinity, though the precise distinction and relation of the terms must still be determined after this foundational theological decision. Indeed, there are even precursors to the identity posited by Karl Barth and Karl Rahner (Torrance 2016: 6–7), but these latter figures become determinative for subsequent trinitarian theology.

3.1 The Trinitarian Revival

The notion of a Trinitarian Revival or Renaissance refers to the explosion of writing and interest on the subject in the closing decades of the twentieth century, following the signal contributions of Karl Barth and Karl Rahner (Schwöbel 2002: 116–118; Oberdorfer 2013: 104). While some challenge the historical narrative undergirding the notion of a Trinitarian Revival (Holmes 2012), it is the case that the doctrine of the Trinity was not a decisive factor in Protestant or Catholic theology at the turn of the twentieth century. Barth and Rahner can be seen as the figures whose contributions initiated this renewal of interest in the doctrine of the Trinity. Barth and Rahner’s decisive insight, despite differing origins and contexts, is the strict identity or correspondence of the immanent Trinity and the economic Trinity. The Trinity comes to be the central doctrine that organizes and determines all others since the supposition of this identity means that theology proper immediately affects the understanding of the divine economy.

3.2 Karl Barth’s rule

The significance of the Swiss Reformed theologian Karl Barth’s doctrine of the immanent and economic Trinity becomes clear in light of the theological context in which he was educated, and from which he decisively shifted subsequent Protestant theology. The majority of academic theology in nineteenth-century Germany was of the liberal Protestant persuasion of such figures as Friedrich Schleiermacher, Albrecht Ritschl, Ernst Troeltsch, and Adolf von Harnack. In this liberal tradition, the Trinity plays a secondary role to primary concerns such as the life of Jesus, a generic theism that emphasizes morality or ethics, or the history of dogma that sees the Trinity as hopelessly bound to obsolete metaphysics (Oberdorfer 2013: 103–104). Many of these decisions result from Enlightenment criticisms of church doctrine and the limits of human knowledge and reason. While there are recent attempts to rehabilitate trinitarian aspects in figures like Schleiermacher (Poe 2017), focus on the Trinity as a central doctrine was the province of a minority, such as the followers of G. W. F. Hegel or mediating theologians like I. A. Dorner. It was this liberal tradition in which Barth was educated and within which he preached prior to his break from liberal theology in the wake of the First World War. Barth did not then abandon the focus on Jesus or ethics that were so much a part of the high liberal Protestants, but he sought a proper grounding that explains why such topics have the theological relevance and significance they have, which he finds in the doctrine of the Trinity and the identity of the immanent and economic Trinity.

Barth places the doctrine of the Trinity at the head of his Church Dogmatics (originally published 1932–1967), in volume I.1 on revelation. Since the God revealed is trinitarian and this is the ground for revelation’s possibility and actuality, the Trinity assumes primary control over the course of Christian doctrine. In a key passage, Barth sets out the ‘rule’ of trinitarian theology that elaborates the distinction and relation of the immanent and economic Trinity:

[W]e have consistently followed the rule, which we regard as basic, that statements about the divine modes of being antecedently in themselves cannot be different in content from those that are to be made about their reality in revelation. (Barth 2010: 479 [vol. I.1])

However, lest one ignore proper order:

All our statements concerning what is called the immanent Trinity have been reached simply as confirmations or underlinings or, materially, the indispensable premises of the economic Trinity [...] the reality of God which encounters us in His revelation is His reality in all the depths of eternity. (Barth 2010: 479 [vol. I.1])

God is Trinity immanently, antecedently, in himself, apart from the world (Barth 2010: 480 [vol. I.1]). The distinction underlines divine freedom and sovereignty, as well as that the Trinity is not a mere created appearance. Nevertheless, God as he is in himself is truly given to creatures to know and trust in the economic Trinity. Throughout this passage, with Immanuel Kant and Ludwig Feuerbach lurking in the background, Barth’s concern is that a gap between the immanent Trinity and the economic Trinity would create an insurmountable problem, since humans have no epistemological capacity to grasp at God and must be given knowledge by God himself – only God reveals God and it is only through himself that God reveals (Barth 2010: 296 [vol. I.1]). Anything other than a tight correspondence of the immanent and economic Trinity cascades into devastating consequences in that God would not have truly revealed himself or have been for us. Epistemology and soteriology collapse apart from this basic premise of the identity of the immanent Trinity and the economic Trinity. This intrinsic identity of the immanent Trinity and economic Trinity governs Barth’s discussion of the Father, Son, and Spirit; the economic appearance of the triune persons points to their antecedent reality in God’s life apart from the world into which he comes in the economy (Barth 2010: sections 10–12 [vol. I.1]).

This receives conceptual expansion in Barth’s doctrine of God proper in Church Dogmatics II.1. In seeking to describe the reality of God on the way to the description of the perfections of God, Barth seeks to understand the statement ‘God is’. Drawing on the act of revelation established previously, Barth argues that the meaning of God’s being is in his act by which he shows who he is. That is, God is not defined by human constructions of a highest being but by his enacted actuality in the economy of grace in which he shows who he is. The key problem is what this action is by which God demonstrates himself to creatures. Barth identifies this in such scriptural affirmations of God as love (1 John 4:8, 16). God seeks and creates fellowship with creatures, communicating his goodness to creatures (Barth 2010: 274–276 [vol. II.1]). This discussion of a key scriptural passage recalls one of the essential elements in traditional discussion of theology and economy, immanent and economic Trinity, in the treatment of the biblical narrative as condensed into the statement of God being love. The movement of the Trinity in the economy is towards the inclusion of creatures in fellowship with God. This movement cannot be a mere appearance or voluntaristic decision; rather, the movement of the Trinity in the economy is the movement of the immanent Trinity as loving fellowship.

Nevertheless, the act of engaging in fellowship with creatures through the Son and the Spirit for the salvation of those creatures is something that is not necessary to God. In other words, the immanent Trinity simply is and requires no manifestation as the economic Trinity in which his purposes are realized for creation.

God loves because He loves; because this act is His being, His essence and His nature. He loves without and before realising these purposes [...] And the point of this realisation is not grounded in itself, but in His love as such, in the love of the Father, the Son and the Holy Spirit. (Barth 2010: 279 [vol. II.1])

The economic Trinity brings about inclusion in God’s loving fellowship, but God is this loving fellowship apart from the economy. The economic Trinity repeats the immanent Trinity in time for creatures and their benefit because God graciously wills to do so. It is gracious precisely because it resides first in God without limit and therefore can be freely given to creatures (Barth 2010: 280–281 [vol. II.1]).

For this reason, Barth considers the act of God to be an act of love in freedom. Behind the economic Trinity is the freedom of the immanent Trinity. This does not mean that there is more God that is somehow still hidden behind his economic manifestation; rather, it signals that the economic Trinity is God’s coming to us for our salvation, and so the immanent Trinity eternally precedes all other occurrence. ‘Within the sphere of His own being He can live and love in absolute plenitude and power, as we see Him live and love in His revelation’ (Barth 2010: 301 [vol. II.1]). This is the freedom of God. God’s loving activity as Father, Son, and Spirit exists wholly apart from all else as his sovereign being. The immanent Trinity is possessed of aseity, absoluteness, and perfection (Barth 2010: 304–312 [vol. II.1]). Lest we think of God’s freedom in libertarian terms, Barth argues that God’s freedom is not merely a standing apart from but a capacity for the creation. The immanent Trinity is sufficient and perfect, but, for the same reason, God can give himself to creation as the economic Trinity. This love and this freedom are found, again, in the missions of the Son and Spirit, which repeat their identities in the immanent Trinity (Barth 2010: 313–321 [vol. II.1]). The economic Trinity is a contingent reality, but it is truly God’s showing himself forth for the salvation of his creatures. The economic Trinity is not necessary for the immanent Trinity to be what it is, but in turning to creation the economic Trinity will necessarily take a certain shape derived from the immanent Trinity.

The effect of this order and identity of the immanent and economic aspects of the Trinity is seen in the two ways in Barth’s doctrine of God. First, the divine perfections are further expressions of this loving in freedom that is the repetition of God’s being as being for us. The divine perfections belong to the trinitarian God and have their form in the life of the Father, Son, and Spirit. This being so, the perfections are not merely relational; they precede their economic manifestation by inhering wholly in God himself apart from the creation. For example, the perfect omnipresence of Father, Son, and Spirit in their order from the Father to the Son in the Spirit is repeated in relative omnipresence to creation centred on Jesus Christ in the power of the Spirit, but God’s omnipresence as sufficient in his triune life is the condition for this relative presence to creation. The identity and order of the immanent and economic Trinity govern all aspects of the doctrine of God in its absolute and relative aspects, and subsequently all things in their relation to God (Barth 2010: sections 29–31 [vol. II.1]).

The second effect of this order and identity is in Barth’s controversial doctrine of election in Church Dogmatics II.2, which he locates in the doctrine of God because, in Reformed fashion, the divine decree is the foundational work of God for creation. In broad strokes, the decision to elect humanity is founded upon the election of Jesus Christ, in which God determines to be God for us. As the immanent Trinity is the foundation for the economic Trinity in respect of the attributes of God, so also the same is found in the action and work of God. The divine decision to take up human nature in the Son has its origin in God’s determination in himself in the being and nature of the Son in relation to the Father and Spirit. Put simply, if the economic Trinity sees the assumption of human nature in Jesus Christ, and through this the election of human beings, the roots of this act and its reason are to be found in the immanent Trinity in which there is this Son that is obedient to the Father (Barth 2010: sections 32–33 [vol. II.2]). The Son’s humble obedience for our reconciliation in the economic Trinity demonstrates the Son’s identity in the immanent Trinity in his filial relation to the Father, which is a major theme and structure of Church Dogmatics IV on the doctrine of reconciliation, alongside the role of the Spirit in applying the benefits of Christ to believers. This has initiated heated and ongoing debate over the meaning and intentions of Barth’s doctrines of election and Trinity, as in the debate of George Hunsinger and Bruce McCormack on whether Barth thinks that God’s trinitarian life is ordered according to the logically prior decree of election or vice versa (on which see Dempsey 2011).

3.3 Karl Rahner’s axiom

Karl Rahner’s doctrine and axiom came about in a much different context to that of Barth. Whereas Barth’s context was that of Protestant liberalism, Rahner’s context was the conservative neo-scholastic Thomism of Roman Catholic theology that achieved dominance after Leo XIII’s 1879 encyclical Aeterni Patris and the anti-modernism of Pius X. The normative use of Thomas Aquinas’ theology and a forceful division of the deliverances of faith and reason was combined with the manualism of Roman Catholic theological schools of the era that produced standardized theological propositions drawn from past thinkers that needed to be memorized rather than argued. While Rahner was influential at the Second Vatican Council and after it, he was not received well prior to the council due to his positive reception of modernist philosophy.

When Rahner addresses the Trinity in a series of essays in the 1960s, his concerns are theological as well as practical. Theologically, the doctrine of the one God could stand alone in Christian doctrine without reference to the Trinity. Firm, hard versions of simplicity and inseparable operations lead to the irrelevance of the Trinity, even in the incarnation. He cites the common teaching of his time that God or one of the Trinity became incarnate, loosening the connection of incarnation and the Son, an unfortunate development of Aquinas’ theology of missions. Trinitarian doctrine was theologically isolated as a collection of necessary, though irrelevant, propositions about God. Practically, Rahner identifies several effects of this theological problem. One is that Christian life and practice in this context reflected, in Rahner’s view, a mere monotheism or practical unitarianism. This can be seen in the address of the Lord’s Prayer, which is directed to the Father but was understood as addressed to God in general. Teaching about the beatific vision of the triune God became unrelated to the experience of faith in the present that was functionally about the one God. The result, in Rahner’s view, is that Christian piety would be thoroughly unaffected if trinitarian doctrine was cast off, therefore functioning apart from the distinctly Christian mystery of salvation. This is aside from the problem that biblical revelation can only make sense in terms of trinitarian dogma (Rahner 1966: 79–87; Rahner 1997: 10–21).

Rahner therefore asserts: ‘The isolation of the treatise of the Trinity has to be wrong [...] The Trinity is a mystery of salvation, otherwise it would never have been revealed’ (Rahner 1997: 21, original emphasis). That is, the Trinity is not a set of revealed, necessary truths about God that are unrelated to Christian doctrine as it reflects the character and movement of God. The theological problem lies in a separation and near-severance of the connection of the Trinity in the economy and the Trinity in God’s absolute life. For this reason, no doctrine is explicable apart from the Trinity. The solution is, for Rahner, the basic, ‘axiomatic’ position of the unity of immanent and economic Trinity: ‘The “economic” Trinity is the “immanent” Trinity and the “immanent” Trinity is the “economic” Trinity’ (Rahner 1997: 22, original emphasis). This is known as Rahner’s axiom or Rahner’s rule. For Rahner, the identity and unity of the immanent and economic Trinity make the best sense of biblical revelation and magisterial teaching, in addition to providing a proper framework for the Christian life in relation to God’s gracious self-communication for the salvation of humans. As self-communication, God’s economic appearance is tied to his inner divine life. Rahner then explains that ‘there is at least one “mission,” one presence in the world, one reality of salvation history which is not merely appropriated to some divine person, but which is proper to him’, by which Rahner refers to the incarnation of the Son (Rahner 1997: 23, original emphasis). It must be the case that the temporal missions in the economic Trinity belong to the divine persons in their processions in the immanent Trinity. The Trinity is the mystery of salvation since it describes the God who is at work in the economy of grace (Rahner 1997: 24).

Given the concepts at issue and their history, it is unsurprising that Rahner’s test case is the reality of the incarnation as witnessed in scripture. Rahner dispenses with the supposition that the assumption of human nature by one divine person indicates that any divine person could have so assumed that nature by reference to personal differentiation. If that was the case, then there would remain something behind the appearance of God in the communication of grace. That is, it would call into question the salvific work of God wrought for us because it would mean that God may not, in fact, have graciously communicated himself, which is the essence of grace for Rahner. The basic presupposition of Christian faith, so far as Rahner is concerned, is that God gives himself to us in graciously being for us and this must mean that his self-communication for us is intrinsically linked with and derived from God’s own life of personal self-communication.

The divine persons, though inseparable and possessed of utter unity of substance, are individual in the sense that they have differing personal properties based on the relations in which they subsist. The Father is unoriginate and begets the Son as his Word (or Logos) and spirates forth the Spirit. Their personal properties differ. For this reason, when encountering revelation in which Jesus Christ, who is the incarnate Son, addresses the Father, this is indicative of the inner trinitarian relation of Son to the Father, and it is his property as Son and Word of the Father to reveal the Father and be sent in this mission (Rahner 1997: 28–30, 83–87). The human nature is the ‘real symbol’ of the Son and not a ‘mask’ put on with no relation to the Son who assumes this nature, which language is meant to denote the unity of the sign or symbol and what is signified: ‘here the Logos with God and the Logos with us, the immanent and the economic Logos, are strictly the same’ (Rahner 1997: 33). For this reason, grace as the self-communication of God to his creatures occurs in the form in which God is in himself – God’s threefold self-communication in the Son and the Spirit is such because God is threefold in the self-communication of the Father to the Son and the Spirit (Rahner 1997: 34–36). The grace experienced in the Christian life that occurs in the history of God’s dealings with creatures in the economy means that that faith and living are shaped by the threefold nature of God (Rahner 1997: 39–42).

As can be seen, Rahner’s point pertains to the necessary logical extensions of biblical revelation that are the conditions for the possibility of that revelatory content. Whatever the motivations of medieval scholastics in asserting the possibility that any of the divine persons could have become incarnate, Rahner’s thesis poses a simple criticism: such a possibility evacuates the meaning of biblical revelation of the Son who becomes incarnate and reveals his divine identity and so also that of his Father and also the Spirit he sheds forth on his people. ‘If we admit that every divine person might assume a hypostatic union with a created reality, then the fact of the incarnation of the Logos “reveals” properly nothing about the Logos himself’ (Rahner 1997: 28, original emphasis). Put in stark terms, if there was no difference between Father, Son, and Spirit in the union with human nature that is the incarnation, then the statements of revealed truth about God are robbed of their content rather than safeguarded, and this undermines the trust that can be vested by the faithful in the grace of God that is sent forth for their salvation. Drawing heavily upon the idiom of the Word or Logos from John 1, Rahner says that the Father speaks his Word, and it is this Word that comes into the world as the Word of the Father. He reveals himself and so also reveals the web of trinitarian relations in which he subsists as a person and into which he brings creatures to participate by grace. Otherwise, Rahner says, we would have to conceive in some way of the Father speaking other than by his Word, which is impossible. To suppose that the Trinity of the economy is detached from the immanent life of the Trinity would

go against the whole sense of holy Scripture. This will be denied only by him who does not put his theology under the norm of Scripture, but allows the latter to tell him only that which he knows already from his textbook theology, cleverly and ruthlessly distinguishing all the rest away. (Rahner 1997: 30)

In simple terms, Rahner is concerned to preserve prima facie scriptural particularity over against philosophical suppositions. Otherwise, it seems, one ought to question the point of scripture, if its content and deliverances concerning this God are not taken as truly reflective of God’s trinitarian being.

Having said this in arguing for his axiom, Rahner is quite careful in what he means by his axiom that identifies the immanent and economic Trinity. He does not mean that God in some way becomes who he is in the progress of the economy of salvation. The reversal of his statement is not intended to place immanent and economic Trinity on equal planes; the identity runs from the immanent Trinity to the economic Trinity. They are inseparable, but there is also an order to the arrangement. It is because the Father self-communicates in the trinitarian processions and relations that the triune God self-communicates to creation as he is in himself in all his unity and personal distinction (Rahner 1997: 34–36, 101–103). In posing his axiom in the straightforward manner that he does, Rahner’s point is that one is not encountering something other than God in his immanent triune life when one experiences the economic Trinity. When one meets the trinitarian God in the economy of salvation, one truly meets the trinitarian God as he is. That this is the case is only possible on the basis of the anterior, perfect existence of the immanent Trinity apart from any economy. The immanent Trinity is the ground of this economy and so can be present in this economy as what it is.

3.4 The interpretation and development of Barth and Rahner

The thesis of the identity of the immanent Trinity and the economic Trinity, as espoused by Barth and Rahner in their distinctive idioms, is a point of departure for all subsequent Western theology. Because of the similarities between their construals of the immanent and economic Trinity, both figures are important points of departure in trinitarian doctrine, irrespective of Roman Catholic or Protestant confessional orientation. The element of necessity in their constructions of this identity and derivation of the economic Trinity from the immanent Trinity is especially noteworthy. Statements like ‘it could have been otherwise’ behind the economic Trinity are impossible on their terms. At the heart of all of this is Barth and Rahner’s desire to preserve what they see as the properly determinative role of scripture’s content concerning the threefold nature of God in all of its particularity.

While Barth and Rahner are the key figures without whom trinitarian theology is not conducted in contemporary scholarship, the development of their thought by subsequent theologians involves a complicated, interrelated set of tasks. There is the distinction between what Barth and Rahner intended, the problems one may find in investigating their foundational work, and what one may wish to say in response or developing their thought. For example, Rahner’s axiom, as stated, could mean many things, and it can be taken up by a variety of positions, as will be seen. Yet this must be carefully distinguished from what is Rahner’s plain position – the priority of the immanent Trinity and proper order flowing from this (Kasper 2012: 275–276; Coda 2020: 73–77). Interpretation, critical reception, and constructive development of Barth and Rahner interweave in the families of views that characterize contemporary discussion of the identity of the immanent Trinity and economic Trinity. Their theses quickly achieved widespread, though not uniform or total, agreement and attention across confessional lines that continue in present scholarship in assessing the nature of this identity relation and its impact on wider Christian doctrine.

4.1 Privileging the immanent Trinity

One set of views develops and extends both Barth and Rahner’s statements and their reasoning in arguing for the priority of the immanent Trinity in the midst of affirming the unity of the immanent and economic Trinity. The motivations for this position can range from concerns about problems arising from a privileging of the economic Trinity or the positive desire to advance the identity thesis in a careful manner. The identity is not a tautology but one of the economic as the necessary unfolding of the immanent Trinity upon the free decision to create; the immanent Trinity is and would be, apart from the creation and an economic Trinity, but the economic Trinity must be a certain way that conforms to the immanent Trinity upon God’s free turn to creation.

A concern shared by this family of views is the apparent room to reverse the order of immanent and economic aspects in the identity thesis. This is expressed by Walter Kasper, a German Roman Catholic academic, ecumenist, bishop, and cardinal. Kasper vests the economic Trinity with significance since there is something that occurs that is new in the economic Trinity, but this is proper to the personal properties in the immanent Trinity; in other words, the processions ground the missions. Reversing the order of immanent and economic Trinity would rob the economic Trinity of any meaning since God would come to be in this relationship, rather than self-communicating for the sake of creatures (Kasper 2012: 275–276). A similar concern is expressed by Yves Congar, O.P., a contemporary of Karl Rahner and influential voice as an advisor at the Second Vatican Council. He observes that, in the reversal or equalizing of priority of immanent and economic aspects, there would be no self-communication if the self is constituted in this relationship; the divine persons communicate themselves as they already are, not in order to be what they will be (Congar 1983: 13–16). Indeed, such a reversal can create the temptation to project one’s desires for various forms of social, political, or ecclesial being onto the Trinity (Gunton 1991: 73–74). Identity can mean many things, but in this case it ‘must be understood as meaning not an identification but rather a non-deducible, free, gracious, historical presence of the immanent Trinity in the economic Trinity’ (Kasper 2012: 276). Cognizance of this priority is, again, not intended to deny the importance of the economic Trinity but to assert that it is God himself that is present in the economy. In some cases, this argument can take the form of explicit revision or correction of Rahner and Barth (e.g. Molnar 2002).

Privileging the immanent Trinity takes up the seemingly inexorable logic of revelation and communication in that the economic Trinity makes known God as he is. The Son’s relation to the Father unfolds in the incarnate life of Jesus of Nazareth, but the reason that the incarnation is of salvific significance is that this economic progression or actualization relies upon the supposition of the anterior consubstantiality of the Son and the Father. Such a position is articulated by T. F. Torrance, a Scottish theologian and student and translator of Barth, who takes up the identity thesis in the appropriation of early church teaching in dialogue with Reformation and modern theology. The one who shares our human nature and shows us the Father in his relation to him is the one who is of one substance with the Father (Torrance 2016). The English Reformed theologian Colin Gunton argues that the persons that communicate themselves in economic Trinity could not have been otherwise than they appear in the economy because of their grounding in the antecedent reality of the immanent Trinity. There is not another possibility behind the economic manifestation of the Trinity; it is God as he is in himself giving himself to creatures (Gunton 2002: 184; Gunton 1991: 137–138). The asymmetry of the immanent Trinity and the economic Trinity is maintained. The immanent Trinity is the necessary and warranted presupposition for the economic Trinity, since God simply is and he as an agent performs saving works for creatures in this way that accords with and derives from his eternal trinitarian life. The economic Trinity is not mere appearance; it is the presence of the triune God as he is in himself even in and through the history he initiates, sustains, and redeems.

In this family of views, there is a desire to underline the ordered nature of Barth and Rahner’s arguments. This is pursued in various ways: in direct dialogue with Barth and Rahner, contemporary theological discussion, and the resourcing of classical discussions. Nevertheless, some room is given to revision of Barth’s rule or Rahner’s axiom for the purpose of more closely aligning the formulae with the substantive argument and to avoid statements that would equalize the order of immanent and economic aspects of the Trinity, often a problem they perceive in another prominent set of positions.

4.2 Privileging the economic Trinity

Another family of views takes the identity thesis as tautological, and therefore they privilege the economic Trinity. As with those that emphasize the immanent Trinity, this is not intended to eliminate the opposite side of the identity. Rather, the concern is to avoid perceived constraints on biblical revelation and to take seriously that God is in fact present in the events in which one finds the economic Trinity. Here, the identity is closer to a reciprocity or tautology in which the immanent Trinity is or requires the economic Trinity in order to be what it is. These views often interpret the history of doctrine in relation to the Trinity as one of biblical deliverances and conciliar vindication followed by decline, fall, and obscurity followed by renewal by attention to biblical revelation.

For example, Jürgen Moltmann, a German Reformed theologian, consciously critiques Barth on the grounds that his biblical theology of self-revelation is not fully extricated from Greek philosophy that overshadows the plain deliverances of scripture. Instead, Moltmann takes the identity to indicate a real impact of the economy on the immanent life of the Trinity. Moltmann is less concerned to maintain traditional views of impassibility and immutability, since he accepts the Hellenization thesis that criticizes the absorption of Greek philosophical thought in early Christian theology as having overtaken distinctly biblical teaching on God. The determination of God to be for us is a determination to take unto himself the full range of consequences of this being for us, especially the event of the crucifixion as determining his inner life. There is a reciprocity between the immanent and economic aspects of the Trinity such that the economic Trinity perfects itself eschatologically into the immanent Trinity (Moltmann 1981). Christology and the theology of the cross are central to such ideas across various thinkers. The idea is that proper attention to the economic Trinity, especially to Jesus Christ and his death, should direct attention to the being of God as inclusive of this economic event in which the distinction of the Son and Father reaches its zenith. Thus, for the German Lutheran theologian Eberhard Jüngel, the event of the cross constitutes the event of the trinitarian being of God because it is in this event that personal self-distinction reaches its greatest extent in love for another (Jüngel 2014; cf. 1980: 265–275). In both of these cases, distinctly Protestant concerns for scriptural priority over metaphysical concerns and the centrality of the cross of Christ converge in a stress upon the reality of the economic Trinity as affecting the immanent Trinity.

In other cases, the distinction of the immanent Trinity and economic Trinity disappears, once again in the interest of proper attention and orientation to the significance of the only reality to which one has access – the economic Trinity in the history of God’s saving works. Revision to traditional orientations of eternity and time enable the construction of an identity that allows for prima facie reading of the economic Trinity that nevertheless is oriented to and founded in the eschatological future (Peters 1993). In the work of Robert Jenson, an American Lutheran theologian and student of Barth, the immanent Trinity becomes the eschatological final outcome of the economic Trinity. God will be who he is and has always been, but he is not this apart from the history that he nevertheless surpasses. The coming forth of the Son in the flesh in time, for instance, is simply the Son; there is no Son apart from the human flesh since the Son is always orientated towards and is this incarnate life (Jenson 2002). The effect of such an absorption into the economic Trinity has wide-reaching systematic implications. Jenson’s doctrine of God proper absorbs not only a theology of the Son and the Spirit but also the historical, saving events of their works. Vast swathes of the economy of salvation are taken up as belonging to the doctrine of the triune God, not merely as indicative of God’s trinitarian life. The external works of God only encompass creatures in terms of creation, the church, and eschatological consummation in Jenson’s Systematic Theology (Jenson 1997–1999).

Thoroughgoing criticism of the insufficiency of Rahner’s axiom by the feminist Roman Catholic theologian Catherine LaCugna, one of the most influential figures of this group, produces a doctrine in which there is only the economic Trinity. The doctrine of God is about God in his movement in and through the world. God just is God for us. There is only this reality. To speak of the immanent Trinity is merely to theologize about the economy of salvation in which God goes out from himself to the world and returns with the world to himself. This also draws doctrine and Christian practice into closer proximity (LaCugna 1991). The identity thesis is, in LaCugna’s doctrine, a full tautology to the point that speech about the immanent Trinity is almost inappropriate since there is no antecedent or prior trinitarian life of God. The immanent Trinity simply is the economic Trinity; there is only this divine reality that exists in and through the movement of salvation history.

A concern in the views that tend towards this end of the spectrum of interpretations and developments is the following: the logical extension from the economic Trinity to the immanent Trinity can involve the same process of going behind the economic presence of God that the identity thesis seeks to avoid, in that metaphysical concerns again seem decisive over against the appearance of God in time as recorded in scripture. Often this is combined with a historical narrative of corruption such as the Hellenization thesis. Even where the immanent Trinity is retained, the Trinity as elaborated in the narrative of the divine economy is strongly decisive and any antecedent actuality is viewed with skepticism as introducing possibility and the spectre of saying ‘it could have been otherwise’. Put another way, any gap between the actuality of the economic Trinity in our experience and the immanent Trinity as its condition of possibility is bridged, closed, or regarded as speculative in a problematic sense.

4.3 Balancing the immanent and economic Trinity

There is arguably a mediating position between the two poles just outlined that can assert the primacy of the immanent Trinity and the full reality of the economic Trinity. Though less represented in the literature, it is central to the trinitarian theology of the German Lutheran theologian Wolfhart Pannenberg. For Pannenberg, the reciprocity of the persons means that God becomes involved and becomes subject to the necessity of executing his lordship over history that is fulfilled at the eschatological completion of time. The linking of the immanent and economic Trinity pertains to the whole course of the economy, not merely to the event of the cross or the incarnate life of the Son. God truly involves himself in the history of creatures and must actualize his lordship over it in order to be who he is, but only on the supposition of his free turn to a creation. Thus Pannenberg does not wish to press the identity thesis into a tautology because he argues for the priority of the immanent Trinity and the significance of the economic Trinity in bringing creatures into fellowship with God. The economic Trinity still only has its meaning and significance, even in a heightened sense, because it is the immanent Trinity whose personal properties and relations come to be expressed through the history of salvation. In willing a world and willing to be God for this world, God will be who he is and will involve the world in his immanent trinitarian life. However, this has significance only for creatures as they come to be brought into participation in the trinitarian life of God; the immanent Trinity is not affected, enlarged, or completed by the economic Trinity. The movement and dynamism of the economic Trinity is necessary for creatures, but not for the immanent Trinity (Pannenberg 1991: 300–336, 442–448). A similar model prioritizing God’s immanent life while emphasizing the dynamic way in which the economy incorporates creatures is found in the idea of God as conversation in the work of the late German Lutheran theologian Christoph Schwöbel (Schwöbel 2011: 451–478).

The degree of success of such attempts to balance the two poles of the debate on the identity of immanent and economic Trinity is up for discussion. Nevertheless, they indicate that the strongly polarized sets of views that are weighted towards ends of the spectrum of possible doctrines need not be totalizing in theological discussion. There is the possibility of space in theological reflection for positions that accept the terms of Barth and Rahner on the identity of the immanent and economic Trinity while also mediating between the two dominant positions on the matter. More work on this may prove fruitful in evaluating the rich theological possibilities that may exist for such a third way.

4.4 Challenging the identity thesis

There are a variety of views that oppose the identity of the immanent Trinity and economic Trinity. The thesis of identity as shaped by Barth and Rahner and inherited in the positions outlined above is challenged on many, differing grounds.

Eastern Orthodox theology, which continues to use the concept of divine energies, generally does not follow the conceptual cloud of the immanent Trinity and economic Trinity, mostly for reasons of the sources, history, and genealogy of Eastern Orthodox doctrine, as mentioned earlier. The trinitarian relations in which the divine energies subsist are those which are bestowed upon the creatures for their participation. Creatures, in the process of theosis/deification, become like God but do not engage the divine essence itself; creatures do not become God but partake of his operations. There is not an immanent Trinity and economic Trinity; there is the Trinity of persons and their relations that share in the one essence and the divine energies that subsist in and through them as the primordial fact of Christian existence and faith. The energies that exist and operate in and through the trinitarian persons and their relations bring creatures into the presence of an utter mystery (Lossky 1973: 23–90; Lossky 1975: 13–30). For this reason, Eastern Orthodox theology can dwell upon the divine persons and relations in a slightly more straightforward manner since the distinction lies in the essence and the energies and not in aspects of the Trinity. It can largely do without a concept of the immanent and economic Trinity in its conceptual work (e.g. see Zizioulas 1985). While there is not usually an explicit critique of the immanent and economic Trinity or the identity thesis, there is a continued, widespread refusal on the part of Eastern Orthodox theology to accept the Western terms of the discussion. This may indicate alternative routes of theological exploration, but it may also indicate a limitation or opportunity to engage its possibilities for ecumenical trinitarian theology.

Another critical approach emerges from traditional Thomist and neo-scholastic theology. An earlier Roman Catholic critic like William J. Hill, O.P. is less than enthusiastic about the agenda of much modern theology, especially Barth and Rahner. His questions arise from a distinctly Thomist view of the linkage of processions and missions. His concern is that an identity of economic and immanent Trinity, and the narrow sense of consequent necessity obtaining in this relationship, posed in the terms of Barth and Rahner, compromises the freedom of the immanent Trinity, such as the freedom of all persons and fittingness of the incarnation of the Son. For this reason, Hill reasserts a Thomist doctrine of processions and missions (Hill 1982). Arguably, Hill does not do justice to Barth and Rahner, among many other figures, largely as a result of his slanted views; one need only recall the distinction between what Barth and Rahner intend and argue as opposed to what their statements could be adapted to mean. Yet sophisticated theological grounds can be supplied for a theological argument similar in outcome to Hill’s work. There is a singular reality of the Trinity whose processions terminate in missions, rather than an apparent double reality of two trinities, entirely rejecting the immanent and economic Trinity as terms (White 2022: 547–587; Emery 2011).

Other approaches are historiographical or interpretive in nature. A historiographical approach goes behind the Trinitarian Revival as a whole to query the nature of the questions being asked by Barth and Rahner and their theological heirs. For instance, the Baptist theologian Stephen R. Holmes argues that the grounds of the Trinitarian Revival and its narrative of doctrinal history do not hold. The doctrine of the Trinity was not lost and irrelevant at the dawn of the twentieth century, Holmes says, and so this casts doubt upon the theological responses supplied by Barth, Rahner, and company because the questions they seek to address are dubious at best (Holmes 2012). Even if one pursues an interpretation of, for example, Rahner on his own terms, such analysis may yield a reading of the identity thesis that indicates that it is, at best, trivial and uninteresting in its theological content beyond already-existing trinitarian doctrine (Rouser 2005).

Strong theological objections are also posed from vastly differing theological quarters. A moderate correction is offered by the American evangelical Fred Sanders, who proposes that the instability of Rahner’s axiom should be resolved in conceiving of the economic Trinity as the image or icon of the immanent Trinity, a secondary but nonetheless true reality in which one encounters God as he is, not unlike the biblical idea of Christ as the image/icon of the invisible God (Sanders 2005). Nervousness about the impact of the thesis of identity of the immanent and economic Trinity as undermining the proper order and assumptions that can be made on the basis of the economy undergirds the trinitarian theology of John Webster, the late British Anglican theologian, and these same concerns appear to drive Katherine Sonderegger’s ongoing systematic project (Webster 2016; Sonderegger 2015–2020). More thoroughgoing critique can be found in the work of Roman Catholic theologian Karen Kilby, who rejects these modern developments in favour of a more modest, apophatic approach to trinitarian doctrine that emphasizes the disjuncture of the reality of God and this comprehensibility of this reality by finite creatures. The Trinity is a central mystery but also one that exists at the limits of theological knowledge. The economy cannot be supposed to indicate great detail about the immanent Trinity, and for this reason it cannot serve in the foundational or determinative role into which theologians of the Trinitarian Revival press this doctrine (Kilby 2020).

The wide range of critical views is indicative of the live nature of the debates on the immanent and economic Trinity in contemporary theology. Given the vastly differing reasons and approaches represented by those challenging the identity thesis or even the immanent and economic Trinity as conceptual tools, it is difficult to assess the strength of these proposals, and ecclesial and academic context are determinative here. Whether or to what degree these skeptical views take hold is yet to be determined.