Here I summarise some aspects of the Trinity by other theologians of more recent times. Karl Rahner, Kalistos Ware, and Wolfhart Pannenberg

Karl Rahner (Catholic) 

(from his Foundations of Christian Faith)

Often God is invoked in the singular and when we think of “God became man” we may also possibly imply something singular. Yet the church is a confessing church of the Trinity and we should always think that way. When it comes to the Incarnation it is specifically the Logos that undergoes the union in Christ and not the Father or the Spirit. So also, salvation comes from the Word who is in Christ (albeit with the union of the others as there can be no separation). Creation and Salvation are a co-operative act. 

The Greek tradition would have us start with the Father as origin of the Trinity (also Scotus) and the Father’s essence becomes shared with the Son and the Spirit. If God is revealed as Trinity then this has left its mark in the OT as well, as the Word comes to speak to the people of Israel as Adonai and the Angel of the Lord. There is no distinction between the “economic” and the “immanent”. The God who is revealed in Jesus immanent in the world is the God who is always Trinity. 

The communication of  divine grace and the self communication of God is a Trinitarian one. There are interior relations between the persons and thjese cannot be thought of in modal ways. What we find in revelation is the secret of these relations between them and with us. It is an existential discovery and not just a theoretical construct to boggle the mind. 

Perhaps we have difficulty with the concept of God as Trinity because of the concept of three “persons” who cannot be persons like us. At the same time we should guard against “three-ism”, three separate entities. There is a specific unity of essence in God that avoids this. We must affirm the three-fold nature of infinite essence that is like us but not like us and transcends individuality. Thus it is that the transcendent mystery of the divine being is Trinitarian. 

Are there aspects of the Trinity that have been revealed before the Incarnation? The Old Testament has strong hints of God as mystery beyond images, unable to be fully known, and yet God converses with humanity. God is represented in “The Angel of the Lord” and by the power of the breath of the Spirit. The Torah and Wisdom are both expressions of the Word given to the community. The Angel is the one who reveals and the Spirit gives power and life. These both reveal what would not otherwise be known of God. Both go “out” from God for an accomplished purpose. These then are pre-Christian understandings of agencies of God without being separate from God or separate gods. There is a unity of nature and unity of will and purpose expressed through them. 

The mystery of the Three persons is also the mystery in which we find our own origins and purpose in life. We discover what we are to be as the Word proceeds from the Father to come to us. The Spirit awakens us and empowers us and interacts with our will.

We may ask if such differentiations that are outlined really exist in God or is it only our perceptions and beliefs? Are they truly part of God’s self-communication? There cannot of course be a proof of this. This is how it has appeared us and been received by us in revelation. We can say that we have observed what appears be such internal differentiation, experienced and received by faith. 

We can also ask if the concept of different “persons” is helpful today as it was in the past? Is it three distinct “selves”? Yet God is infinite and hence we have three infinite “selves”. Theological tradition asserts there is no multiplication of the essence. We cannot speak of “persons” as we know finite persons. Yet we must accept the appearance of differentiations within the infinite essence and this brings an inadequacy of language and definitions. It is a unity of different expressions of God that is not simply modes of the same reality and therefore not modalism

Kalistos Ware (Orthodox)

The doctrine of the Trinity is not just a piece of theology reserved for scholars but is something that is about living for every Christian. It contains a social program. God is Trinity and hence, as we are “created” in the image of God we are “created” to be the image of the Trinity. We are to be people of the Trinity. Only in  the light of this dogma can we be what we are intended to be. All about our personal and social lives depend on a right understanding of the Trinity. It is an ever new way of thinking about God and the world. 

God transcendent but also found in the world. There is a  difference between the “essence” of God (that is beyond all) and the “energies” of God (found in interaction). God’s energies come to us while the essence remains beyond us. We have a Trinitarian God who is hidden but who acts and intervenes (causes etc). God 

God as Trinity is a ”personal God” and we are brought to face a God who is not some vague force, but personal, indeed a Trinity of persons. Each “person” of the Trinity dwells in the others with a perpetual movement of love. The Trinity is not simply a unity of persons but a union of persons. 

God is a God who becomes Incarnate. The Trinitarian God has also come to us in “His” person, “made man”. This is closest union that can exist between divinity and flesh. 

Those brought up in other traditions have sometimes found it difficult to accept the Orthodox emphasis on apophatic theology (that God is unknown) and the distinction between essence and energies; but apart from these two matters, Orthodox agree in their doctrine of God with the overwhelming majority of all who call themselves Christians.

Yet there is one point in the doctrine of God the Trinity over which east and west part company — the filioque.  This one word played in the unhappy fragmentation of Christendom. But granted that the filioque is important historically, does it really matter from a theological point of view? Many people today — not excluding many Orthodox — find the whole dispute so technical and obscure that they are tempted to dismiss it as utterly trivial. From the viewpoint of traditional Orthodox theology there can be but one rejoinder to this: technical and obscure it undoubtedly is, like most questions of Trinitarian theology; but it is not trivial. Since belief in the Trinity lies at the very heart of the Christian faith, a tiny difference in Trinitarian theology is bound to have repercussions upon every aspect of Christian life and thought. Let us try therefore to understand some of the issues involved in the filioque dispute.

The persons are “one essence” but have different personal characteristics. The divine is indivisible. The persons are united but not confused. (cf distinction of the Word and roles the Word undertakes in Bonaventure etc). This is paradoxical but true. 

But if each of the persons is distinct, what holds the Holy Trinity together? Here the Orthodox Church, following the Cappadocian Fathers, answers that there is one God because there is one Father. In the language of theology, the Father is the ‘cause’ or ‘source’ of Godhead, He is the principle (arche) of unity among the three; and it is in this sense that Orthodoxy talks of the ‘monarchy’ of the Father. The other two persons trace their origin to the Father and are defined in terms of their relation to Him. The Father is the source of Godhead, born of none and proceeding from none; the Son is born of the Father from all eternity (‘before all ages,’ as the Creed says); the Spirit proceeds from the Father from all eternity.

So what holds the unity together? It is the Father as the source of the other two persons. The Father is the origin and source of the Godhead (the primary producer). The Principle among the three. The Monarch of the three. (as in Scotus etc). The others defined by their relationship to the Father. The Son and Spirit “proceed” from the Father from all eternity. 

Th dispute is what is meant by “proceeds”. Christ had two births. One eternal (as the Word) and one in time (in the incarnation). In the same way there is to be understood the eternal procession from the Father before all time, and being sent in time to the world for temporal mission in creation and redemption. Here again the difference between the eternal procession and the temporal one. 

The question is about the eternal relations between the persons prior to their temporal sending and being sent. While it is true in temporal terms the Spirit comes at the equal behest of the Son, in eternity the Orthodox say the Spirit is the product of the Father alone.

Wolfhart Pannenberg 

(Notes from Systematic Theology Vol 1)

Jesus in His talk about the Kingdom of God and His own discourses about God calls God “Father” (actually Abba), caring, loving and forgiving. Elements of Jewish religion had also called God “Father” but not as personally as Jesus. For Jesus “Father” is proper title and designation of God. It cannot be eliminated from the message of Jesus because it is about divine love and relations. It is expressed His closeness to the Father, linked to Him but differentiated from Him. He is the Son in nearness and subject to the F’s will. The resurrection confirms this relationship and an eternal relationship that is also about a pre-existing state. 

Jesus deity is also linked to the title “Kyrios” (Lord) that implied the deity of God and divine lordship. It was used by Christians in prayers and statements that did not conflict with the deity of the Father. The Spirit as creative agent was also related to God and a mediating presence in the life of the believers. The Spirit also found acting in Jesus and having a role in His resurrection. There is then the early baptismal formula found at the end of the gospel of Matthew that was about Father, Son and Holy Spirit. Hence in the early church these associations were already found in the profession of the church. 

Paul may have sometimes seemed to have blurred the distinctions between Jesus and the Holy Spirit as the “Spirit of Jesus”. But John was quite clear that the Spirit was “another advocate”. It was thus these distinctions and led to the later needs of the church to define the relationships but remaining monotheist. The Word and Spirit come to be seen as two distinct divine agencies of the Father. Thus then (as in Athanasius) the Word and Spirit co-operate in the work of mediating God to the world and a joint participation of Father, Son and Spirit in all divine activity. This then in the biblical texts is the foundations of the revelation of the inner life of God and an inner life that actually comes before everything that God has done and does. 

There remained in the church for some time a tendency of subordinating the Son and Spirit to the Father in order to maintain monotheism, but this was resisted by the main church Fathers, so that the Son was eternally begotten, having always existing and not having a time of coming into existence from the Father. There was also the use of the Old Testament to show that these active agencies were present before the birth of Jesus and had always been part of the way God had acted in the world. 

Reformed theology inherited this tradition but wanted to go back beyond the church traditions and creeds back to the biblical texts to justify it all. It involved fresh looking at the biblical texts about Jesus, the God as Father and the Spirit experienced by the discioples. Such textual analysis led to some anti-trinitarian movements and discarded the scholastic arguments. But it was also shown that a thorough Trinitarian doctrine could be maintained from scripture even without the later Orthodox and Catholic elaborations. Later Reformed theologians have continued to find justifications for a Trinitarian understanding of God. The “immanent” (what is seen of God) is truly related to what is in God essentially. There is a real reality in God that is shown in the life of Jesus and the life of believer’s experience of the presence of the Spirit. 

There is revelatory character to doctrine, that arises out of what was seen in Jesus. Reformed theology goes back to basics of scripture rather than speculative theology. What God had revealed in Christ is how God is in God’s self in eternity. Yet this is no simple matter given critical study of the bible, especially in relation to the Old Testament.

There are scriptural statements that the Father is known (made known) through the Son and by the inspiration of the HS. There is also the lordship of God revealed in Jesus, and the sending of Jesus to reveal God. The distinctions between Jesus and the Father show the real distinctions within God and the prior relations in God. The Farther alone is without origin and the Word and Spirit have their existence from the Father.

The Spirit glorifies the Son also glorifies the F. We must insist on the mutual love in God and as a distinct centre of action from God. But the relationships of origin are only a starting point as they interact in divine history. There is a real sense in which the Son in the life of Jesus is subject to the Father  is always subject to the Father in eternity. The Son always does the will of the Father . The Spirit always gives glory to both, All things begin with the Father even if all action is shared. 

Conclusion

The three theologians here confirm the importance fo the Trinity as an important article of faith about what we have come to know of God, as both one and three. The delve into the inter-relations of the persons in God from both biblical , traditional and philosophical traditions. There are differences of emphasis and we must today come to deal with such differences that may divide the church. It is my belief that such differences from past history and  traditions need not to be an obstacle to unity.