Karl Rahner (1904-1984) was one of the most influential theologians of the twentieth century. His work, alongside other important theologians like Hans Urs von Balthasar, helped to overcome the dusty sentences of Neo-Scholasticism and usher in a great flowering of theology. Turning his mind to the doctrine of the Trinity, his contributions are no less potent. In a short work, no more than 120 pages, Rahner helps revitalize Trinitarian theology.
At the center, he strives to demonstrate two key insights. The first is the necessary connection between soteriology (the doctrine of salvation) and the Trinity, that is, the unfolding of soteriology along necessarily Trinitarian lines. In so doing, the relationship of the processions to the economy of salvation eschews all scholastic questions or presuppositions that the position of the Persons in the divine economy is interchangeable. That is Rahner's overriding axiom, “the economic Trinity is the immanent Trinity.” His second insight, which might appear as an afterthought, is to clarify the use of the word “person” in dogmatic theology. Rahner proposes a new formulation, which he believes will help to strengthen the term.
What follows will summarize and analyze the threefold structure of Rahner's work, The Trinity. In the first section, he addresses the classical approach to the treatise De Deo Trino. In the second section, he turns to the official teaching of the Church. Lastly, he sets forth his own “systematic outline of Trinitarian theology.” We will conclude by proposing a few challenges and answers to Rahner's overall contribution.
The Method and Structure of the Treatise “On the Triune God”
Rahner laments that work on Trinitarian theology has slackened since the Middle Ages. Even the Second Vatican Council, mentioning the Trinity in the context of salvation history, merely connects the doctrine biblically. It does not propel it forward. It appears to Rahner that to the average Christian, the separation of the doctrine of the Trinity from everyday life has left it a dead letter. Thus, he hits us with one of the most brutal conclusions of the whole text,
Christians are, in their practical lives, almost mere “monotheists” . . . We must be willing to admit that, should the doctrine of the Trinity should have to be dropped as false, the major part of religious literature could well remain virtually unchanged.
In every area of theology, the Trinity has been divorced, left as a pious addition to the faith with no practical purpose. Even the doctrine of the Incarnation has been reduced to “God becoming man,” as if the sending of the Son was an arbitrary or interchangeable choice of the Persons. Even more, how can the Trinity, which is the fullness of the Beatific Vision, matter in eternity if it does not matter in history?
These questions lead Rahner to critique the relationship between the classical treatise De Deo Uno and Deo Deo Trino. Rahner notes that this organization of theology becomes popular in the wake of Thomas, but that he believes it would help the problem if we followed a more scriptural, Eastern approach. Namely, by beginning with ὁ Θεός. With scripture, we could read ὁ Θεός as the Father and subsume the discussion of the divine essence under the rubric of the Father who shares it out in the processions. In a way, the old approach merely moves the divine essence ahead of the discussion of the Father. Still, even this minor movement opens up the possibility of seeing the Trinity as posterior to the divine essence, introducing a fourth term and the possibility of modalism. While understandable in a Thomistic scheme, beginning with the divine essence leads to more problems than Rahner seems to believe its worth, especially since the organization of the treatises means the Trinity cannot have any relevance outside Christian revelation.
The isolation of De Deo Trino is inappropriate, then. Ecclesiology, soteriology, Christology, and anthropology must be understood as Trinitarian. Rahner believes that each of the classical dogmatic treatises would collapse if they were stripped of their Trinitarian origin and structure. Why? Because the Trinity is a (the?) mystery of salvation. Here we come to that central axiom that Rahner proposes, “the ‘economic’ Trinity is the ‘immanent’ Trinity, and the immanent Trinity is the economic Trinity.” No longer an afterthought, the Trinity must assume a place at the center of all Christian dogmatics, especially salvation, or Christianity will wither.
Rahner next turns his attentions to justifying his axiom. This axiom is de fide in his view. It is explicit in Scripture in the person of Jesus. The Son, not the generalized Godhead, who has made a salutary act for us. Thus, in the economy, some degree of the relations of the immanent Trinity are maintained. This does not answer all our problems or prove a strict identity between the two. Still, it properly distinguishes a connection between the two and shows how one cannot simply bracket out the Trinity as an intra-divine reality with no effect on man.
Addressing counter proposals, Rahner clarifies his axiom even further. For example, some claim that the hypostatic union is a special instance from which no general principles about the Trinity can be abstracted, except that it is only through a hypostatic union that a single divine person can have a proper relation to the world. It would follow that each Divine Person could enter a hypostatic relation to the world. Responding, not only does he reject this view as unsupported by Scripture or Tradition, he suggests that we might ask if it is not in the peculiar nature of the Second Person to be in a hypostatic union, that it might be the mode of his existence in the self-communication of God to be the one who becomes man.
This would mean that the Incarnation not only reveals the Trinity, not only reveals the Second Person but tells us something about the eternal nature of the other Persons, namely, that their subsisting manner is not to be incarnate. Thus, the Incarnation is an instance revealing a proper economic relation of the Three Persons to the world (each in their peculiar way). Since the whole Trinity acts properly, the whole Trinity is revealed, and his axiom stands. In a subsequent argument, Rahner defends the nonincidental nature of the humanity of Jesus as well. His humanity tells us something about him, just as the fact that the Second Person was incarnate tells us something about God.
Rahner now turns to God's self-communication. Given what he has already said, he points to the fact that the actions of the Triune God are one, though the distinct manner of each Person's activity may be different. Thus, each Person can relate to humanity in a distinct way. This communication, which certainly includes creation itself, is the ground of our existence and our end. In this self-communication, each of the Persons gives themselves to each other as they are, according to their proper relation. In the same way, they give themselves to us (according to the axiom). Thus, the Father gives himself to us as Father, etc. Scripture, according to Rahner, demonstrates the divine self-communication as three-fold.
- That which is given remains sovereign (that is, what is given cannot be circumscribed, even though we possess it as fully as possible).
- It is a communication in which God freely is there, a historical act of his true self-communication.
- It is a communication that causes, in the willing recipient, welcome and love, but again preserves the sovereign transcendence of the one communicating. (It is not a love of equals).
This model of self-communication is of structural importance for the remainder of the text. He cautions us to keep in mind that God's self-communication is not merely verbal. There is a real distinction between the Word spoken (Logos) and the love engendered in response (Spirit). Further, Scripture and Tradition indicate this double mediation is not merely a created reality for our benefit. It is an essential property of the Trinity in itself.
Rahner's overall point in laying out this section is to demonstrate that salvation history has a Trinitarian shape and that “Man understands himself only when he realizes that he is the one to whom God communicates himself.”
The Main Lines of Official Trinitarian Doctrine
Next, Rahner turns to the doctrine of the Trinity as the Church has defined it. This will offer him the backdrop for his own formulation in section three and demonstrate a continuity between his own approach and the historical tradition.
In the first place, no matter the advancements of theology, it must be remembered that the
Trinity is an absolute mystery, which cannot be understood even after its revelation. The Magisterium has seen fit to explicate this mystery by the use of different terms, each with its own specialized meaning: person, hypostasis, essence, nature, etc. However, when these concepts approach the Trinitarian reality, they tend to break down, only to be understood in the context of the whole, and even then only in a minimal way. For example, person and essence, while having concrete meanings when particularly applied to human beings, only generally describe the divine reality revealed in Scripture. They touch on the distinction between the incomprehensible nature of the Father, which is given entirely to the Son and Spirit. Beyond that clarificatory use, their meaning runs aground. All language applied to the Trinity is at risk of the same fate. It helps to stave off heresy but is eventually lost in the “dark mystery” of God.
Later, Rahner will deal with whether it is possible to replace the concept of “person,” mainly because of the complication of its use after the Enlightenment. Here, he points to the doctrinal flexibility when using this particular language but recognizes that it is unlikely to allow for a complete dropping of words used for so long in the Church's tradition.
Next, we are given a summary of the central doctrinal statements on the Trinitarian God. He begins with the Father, as is his preference, and moves from Person to Person. It is not necessary here to recapitulate the whole of the Church's doctrinal statements, but some crucial areas of Rahner's analysis are highlighted.
First, Rahner is insistent that we understand ὁ Θεός as the fons divinitatis. This preserves the idea that each Person of the Trinity reveals themselves as themselves and according to their own manner. Thus, in the Old Testament, the Father is active, and the Son and Spirit, while certainly active, are inchoate. They are not explicitly revealed (and so Rahner follows Augustine on this point). Each Person reveals themselves according to the manner of their own subsistence.
Concerning the Son, it is vital that we remember that Jesus understood himself as the concrete man, as the Son, as Messiah in a special way, the one to bring salvation. The Son, in so far as he is the bringer of salvation, is the total self-communication of the Father to the world and in such a way as if the Father were there. The Son is the economic self-communication of the Father. Rahner is intent on showing that we can move from the economy to the inner life of God. Still, it should be noted that sometimes this emphasis can appear so intense that one wonders whether the economy is not driving the inner life.
Rahner reclaims the Stoic distinction between the inner word and the expressed or uttered word when speaking of the Son. This distinction was certainly present in the Church's doctrinal tradition and is essential to his understanding of the Son's role in the double aspect of the divine self-communication.
Regarding the Spirit, the Tradition holds that he is the gift of the Father through the Son in which God is communicated directly to us and is the cause of the acceptance of the Son in us. The experience of Faith names “the Holy Spirit” as that through which we receive love and forgiveness from God. Just as the Son is uttered Word to us, so the Spirit in the love of God in us. The Spirit relates God's self as love to us and dwells in us as that love.
When thinking about the distinct members of the Trinity, the Church does not furnish us with a strict definition of hypostasis or a clear definition of person, though he thinks person adds nothing to hypostasis, Rahner proposes that we might understand hypostasis in two ways:
- Three Concrete Ways of Being Given, Givenness (Economic)
- Three Ways of Relative Concrete Existing for the One and Same God (Immanent)
The Son and Spirit are not merely modes of this eternal givenness either, but subsistent realities of that givenness and conversely establish the Father as Father, the one who has given. In the same vein, we must avoid proposing three subjectivities when discussing hypostases and persons, lest we fall into tri-theism.
A Systematic Outline of Trinitarian Theology
In his own systematic approach, Rahner bypasses the classical questions of Neo-Scholasticism and isolates two themes that he considers of prime importance, 1) an analogical understanding of the Trinity, which proposes an ontological structure to creation and salvation history in general, and 2) a new way of conceiving the concept of “person.”
Naturally, he begins with his Grundaxiom, that the “economic Trinity is the immanent Trinity” and vice versa. In Scripture, the economic Trinity manifests in two distinct ways, the self-communication of God to the creature in a) Jesus Christ and b) the Spirit. These modes form a kind of taxis, one necessarily following the other. How are we to understand these two “moments,” the communication of the Son and the Spirit in the one self-communication of God?
Rahner thinks that Catholic theology is not concrete enough. There must be a necessary connection between Son and Spirit such that they could not simply be interchanged. He believes it essential that it be the Son who is incarnate and the Spirit who draws the world to the acceptance of the Son. This necessary interconnection of the Incarnation and the Sending of the Spirit demonstrates that salvation is Trinitarian.
This necessary connection can be demonstrated by looking at the economic mode of God's self-communication, that is, to see if its double nature is connected. Then, if the Grundaxiom holds, the two-fold nature of God's self-communication to man tells us about the eternal mode of God's self-communication. Rahner gives us a list of four aspects that reflect the two-fold nature of God's self-communication to man. Properly understood, this leads us to their eternal “doubleness.” 
He defends the connectivity of each first term to its second and the unity of all the first terms and second terms among themselves.
In accordance with our own nature, revelation has an origin and a future. Rahner understands creation to have been made with man in mind, that it was created with a view to generating the recipient of God's self-communication. According to the Divine Will, we have a beginning and a future at which to aim, which is the fullness of God's self-communication.
Man considers both the concrete object that he has received and the horizon at which he aims. The object, the revelation, stands in history and yet points man to his destiny. But this does not make the object incidental. For the object is the meeting place of that history and destiny. It travels with man. Its unfolding is the ultimate goal. This self-communication from God only occurs in the space that man inhabits, in history and the transcendent future to which it looks.
Man is free. Though he was created to receive this self-communication from God, he need not do so. Therefore, the self-communication of God looks towards his free acceptance and provides the means for that acceptance.
These two initially seem to be of a different sort than the other three. Rahner, however, sees these as a unity that complete each other. Knowledge, once given, implies some response to it, some activity. If that knowledge is true or truth, then the proper response to it should be love, that will which desires the full goodness and completion of the other according to the knowledge received. This certainly builds on the Thomistic principle that before one can love, one must know. Thus, love completes knowledge.
Rahner tells us that knowledge and love describe the reality of man in himself, and, therefore, God's revelation manifests itself in that mode. It might be better to say that man was created in such a way that he is summed up by the mode of God's self-revelation, which is already eternally present, absolute truth and absolute love.
After spending time defending the unity among the terms on each side of our four aspects, we are drawn to conclude that the divine self-communication possesses two modes, ultimately, knowledge and love. These are ontologically connected, one completing the other. They are, thus, not interchangeable. Rahner has been striving for this view of the Triune action that rises above caprice to a rationality in the structure of creation itself. The historical revelation of the Truth (knowledge) presupposes a horizon at which that Truth aims, namely the future, transcendence, acceptance, Love.
Having laid out the three-fold manner of the divine self-communication in creation and the ontological connection between its constituent parts, Rahner turns to how this economic Trinitarian revelation is connected to the immanent Trinity. He asserts that the economic must be the immanent, his Grundaxiom, because otherwise, God would not have been self-communicated. What we would have received in the Incarnation and gift of the Spirit would be only mediations of God's presence, not God himself. Thus, in the giving, he would actually take away. Therefore, if we are to understand God's self-communication as the giving God himself, as Scripture and Tradition demand, these economic modalities must stretch into the divine nature itself.
Following this logic, every creative and salutary activity of the Godhead is essentially, not incidentally, Trinitarian. They proceed to us from the Triune God, in the mode of the Triune God, and return to the Triune God. This self-communication of God, which enfolds our history, our cultures, our fall, our salvation, and our death, is met by the Son, utterance of the Father, and we are drawn up into him by the Spirit, who makes us partakers of his body and joins us to his Ascension back to the Father.
The second task that Rahner takes up in this short text is to propose an adjustment to the use of the concept of “person” in theology. Terminologically, the fact that “person” is not used ab initio is not itself a problem. Still, it does allow us to propose that it may not be indispensable to the doctrine. This matters because the word is riddled with baggage in the modern age. In part, because of this, the analogical relationship between divine personhood and human person breaks down. Take the much-loved Thomistic definition, “a subsistence in a rational nature.” It, applied to the Trinity, unintentionally multiplies the natures. Ultimately, the use of the term was a help to avoid the errors of modalism, but is, itself, empty of specific meaning when applied to the Trinity.
Today, the problem is that we assume person means a “spiritual or psychological center,” as it does when referring to humans. This would multiple the centers of subjectivity in God, leading to a de facto tri-theism. Ontological personhood must be understood differently, as the one God manifested in three persons, those persons being self-aware, but not with different natures or essences or powers.
So we are left with a word that clouds more often than it reveals. Rahner admits that the theologian cannot dispense with this word of his own authority and therefore must attempt to clarify it. This is where he believes he can be of help.
Turning back to his insights on the word “hypostasis” in the previous section, he asks what a new “explanatory concept” might look like. Economically, the self-communication of God comes in three manners of givenness. Immanently, we could say that the One God subsists in three “distinct manners of subsisting.” He does not mean to supplant the concept of person but to clarify that personalizing aspect, the manner in which God meets us at this one. Person would then be understood as God meeting us in this distinct manner of subsisting. Subsisting implies that God is meeting us as “being-thus-and-not-otherwise,” but also that God is the same God who meets us in another “being-thus-and-not-otherwise.” Thus, the need for proper nouns to distinguish the different beings-thus.
This transcends the concept of person by itself in that “distinct manner of subsisting” implies a unity among the manners, the “relationality.” It is important, Rahner tells us, to avoid the idea that manner suggests a unified God that exists before those manners, some fourth term. The manners are the way God exists. There is no pre-manner reality.
Giving examples of how the use of this new concept could strengthen basic doctrinal statements, Rahner still resists the suggestion that we replace “person” with it, though that is how some read him. He thinks “distinct manner of subsisting” can ultimately be a tool that helps to clarify the use of person in reference to the Trinity.
Conclusion: Some Benefits and Challenges
One of the great benefits of Rahner's system, despite its technical nature, is that it proposes a structure that not only connects the Divine Persons to their economic mode of revelation necessarily, but that connects the entire structure of creation to a Trinitarian architecture. No longer can we simply ignore the Trinity when looking at Christology or soteriology, or ecclesiology. No, not only must we see the Trinitarian contour in each sub-discipline, but we must recognize that they would collapse if removed from their Trinitarian framework.
Still more, Rahner's short discourse on personhood takes the problem of the term head-on. It is not clear that the distinction he makes will be of use outside larger academic circles, but it may help structure the minds of those to whom falls the responsibility of transmitting these mysteries more broadly.
There are risks, of course. Rahner's language, particularly in the Grundaxiom, is always open to the risk of a Hegelian or Economic Trinitarian bent, an interpretation which conditions the processions of the Trinity on their interaction with the created universe. This is particularly clear in the second clause, the “vice-versa,” that “the immanent Trinity is the economic Trinity.” It is easy to understand that Rahner wants to stress how vital the Trinitarian doctrine is to all fields of human experience, but we cannot take this second identification with the same strictness as we have taken the first. The result would be precisely that bent we would wish to avoid.
A second problem, of the language, particularly concerning “distinct manner of subsisting,” is that it overgeneralizes the personal nature of the Trinity. This is Gerald O'Collins' critique. He remarks that this hyper-technical academic language leaves us “nothing to adore.” The Rahnerian concept, while helpful to the theologian, is far too abstruse for liturgical and pious use.
In the end, there are many things to commend Rahner's work and many things to critique. However we receive it, the text takes up the challenge of reinvigorating the Trinitarian doctrine for this age of the Church. It responds to Balthasar's lament in Razing the Bastions that the Trinitarian doctrine “seems to have stood still, half-congealed and dried up after Augustine's psychological speculation.” Rahner's work approaches the mystery of God in a way the eschews Augustine's psychological analogy and opens up vistas not yet explored. Whether one loves it or one hates it, it represents a monumental attempt to drive us back to the doctrine at the center of our faith.
 Karl Rahner, The Trinity (New York: Crossroad, 1997), 22.
 In The Trinity, 7, n2, Rahner tells us that this section is an expanded form of “Remarks on the Dogmatic Treatise ‘De Trinitate,’” in Theological Investigations, vol. 4 (Baltimore: Helicon, 1966), 77–102.
 Rahner, The Trinity, 9–48. My section titles match Rahner’s three section titles.
 Ibid., 9–10.
 Ibid., 10–11.
 Ibid., 11.
 Ibid., 15.
 Ibid., 16.
 Cf. Karl Rahner, “Theos in the New Testament,” in Theological Investigations, vol. 1 (Baltimore: Helicon, 1961), 79–148.
 Rahner, The Trinity, 17–21.
 Ibid., 21–22; Gilles Emery, The Trinity (Washington, D.C.: CUA, 2011), 176.
 Rahner, The Trinity, 22.
 Ibid., 23.
 Ibid., 25–28.
 Ibid., 34–35.
 Ibid., 35.
 Ibid., 36–37.
 Ibid., 37.
 Ibid., 40.
 Ibid., 46–47.
 Ibid., 49–79.
 Ibid., 50.
 Ibid., 51–52.
 Ibid., 52–53.
 Ibid., 55.
 Ibid., 57; Gerald O’Collins, The Tripersonal God: Understanding and Interpreting the Trinity, 2nd ed. (New York: Paulist Press, 2014), 155–58, 174–80.
 Rahner, The Trinity, 56.
 Ibid., 58.
 Ibid., 63.
 Cf. ibid., 64.
 Ibid., 64–65.
 Ibid., 66–67.
 Ibid., 75.
 Ibid., 74.
 Ibid., 75–76.
 Ibid., 80–120.
 Piero Coda, From the Trinity: The Coming of God in Revelation and Theology, ed. William Neu (Washington, D.C.: CUA, 2020), 68.
 Rahner, The Trinity, 83.
 Ibid., 86.
 Ibid., 87.
 Ibid., 88.
 Ibid., 90.
 Ibid., 91–92.
 Ibid., 92–93.
 Karl Rahner, “God, Attributes Of,” in Sacramentum Mundi: An Encyclopedia of Theology (West Germany: Herder, 1968), 399.
 Rahner, The Trinity, 93–94.
 Coda, From the Trinity, 69–71.
 Rahner, The Trinity, 98.
 Karl Rahner, “Trinity, Divine,” in Sacramentum Mundi: An Encyclopedia of Theology (West Germany: Herder, 1970), 300.
 Rahner, The Trinity, 100.
 Ibid., 103.
 Ibid., 104.
 Ibid., 105.
 Ibid., 106.
 Ibid., 108–9.
 Ibid., 109–10.
 Ibid., 110.
 Ibid., 111–12.
 Ibid., 112.
 Coda, From the Trinity, 73–75.
 O’Collins, The Tripersonal God, 175.
 Hans Urs von Balthasar, Razing the Bastions: On the Church in This Age (San Francisco: Ignatius Press, 1993), 29.