Historical development of trinitarian doctrine in Roman Catholicism

are couched within the context of multiple theological and ecclesiastical disciplines. By means of an interdisciplinary perspective as applied to a complex subject such as the Trinity herein, a broader perspective is obtained about this core Christian belief and notion of God who is One in substance and Three in persons. This is most notably by locating trinitarian discourse within the liturgical and theological traditions of the Western and Eastern churches.


Introduction
Walter Kasper in his book The God of Jesus Christ makes this bold assertion: 'The confession of one God in three persons is rightly regarded as proper and specific to Christian faith in God' (Kasper 1986:233). The Catholic Church and the Orthodox Church consider themselves as the two surviving arms of the ancient church regarding the creeds and the first seven ecumenical councils before their acrimonious and long-lasting schism in 1054. Considering this fact and in relation to the creeds, both churches can be described as creedal churches. In various manners, they officially, and formally, as well as liturgically, recognise and profess the creeds as formulated by the ancient councils. It is not an overstatement to affirm that both churches rise and fall with the creeds, and at the very centre of it all stands the firm belief in one God in three persons. Reframed somewhat differently, the church's trinitarian doctrine acknowledges that '… in God there is a unity of substance and a trinity of persons or a unity of substance in a trinity of persons' (Kasper 1986:234). As Thomas Weinandy rightly observes, early trinitarian faith and proclamation occurred and flourished within the church's doxological ambience. Thus, within that same ecclesial environment, according to Weinandy (1995): thinking, which in turn has produced an inexhaustible body of literature (Helmer 2003:127-128). It has led, for instance, to rational inquiries and studies about the existence and essence of God as well as speculation on the question of divine attributes and whether or not God is knowable. In the words of Thomas Aquinas , 'knowledge of the Trinity in unity is our whole life's fruit and goal ' (cited in McDermott 2012:113). However, on account of the near presence of heresy, Augustine of Hippo (the father of Western theology) wisely cautioned that trinitarian theology carries the perennial risk of being a complex aspect of inquiry (Letham 2002:35). As he surmised: 'In no other subject is error more dangerous, or inquiry more laborious or the discovery of truth more profitable' (cited in Letham 2002:28).
Over the centuries, trinitarian discourse has produced controversies on its thralls. Amidst debates and contentions, the tag of heresy has wilfully and unwittingly been smeared at opponents of divergent positions. It has generated a considerable lexicon of accusations such as tritheism, modalism, subordinationism, Sabellianism and Origenism. The purpose of this article is not to recount the numerous trinitarian controversies. The aim is simply to trace as much as possible and in a concise manner the evolution of trinitarian theology through the conceptual frame of Roman Catholic tradition. It adopts a historical approach in the comprehension of trinitarian doctrine within the Catholic Church. Considering historical evidence, it concludes that, despite differences in perspectives and emphases, the churches of Latin and Orthodox rites have preserved intact their belief in the Trinity as a common doctrinal and theological heritage of both sister churches. As for the Catholic Church, the rediscovery of the great Easter theological tradition and insights as well as the renewal of positive and historical theology have impacted positively on the development of contemporary Catholic theology of the Trinity. As evident most especially in the area of pneumatology, the article argues that contemporary Catholic trinitarian theology has been further enriched by its attunes to other contemporary trends like history, ecclesiology and ecology. In terms of semantics, Latin and Greek are used interchangeably herein to refer to the Western and Eastern churches, respectively.

Biblical foundations and earliest musings
The Christian doctrine of the Trinity may rightly be described as the church's interpretation of the scripture. In the explication of Fred Sanders, the doctrine is not explicitly formulated in the scripture even though scriptural inferences and allusions about the Trinity are somewhat present in some passages of the Old and New Testaments (Sanders 2005:18). While referring to Arthur Wainwright's Trinity in the New Testament, Sanders expresses the viewpoint that 'the doctrine of the Trinity is not present in the New Testament, but the problem of the Trinity is' (Sanders 2005:19). That fact notwithstanding, Sanders acknowledges that triadic allusions and formulations where they are found in the New Testament usually have their roots within liturgical and confessional settings (Sanders 2005:19). Two classical examples are as follows: firstly, the baptismal formula that is found in Matthew (28:19) where the gospel writer makes Jesus instruct his disciple to baptise 'in the name of the Father, and of the Son and of the Holy Spirit'. Secondly, the liturgical greetings addressed to the Pauline community in the city of Corinth: 'The grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all' (2 Cor 13:13).
As a very central mystery with scriptural basis, the belief in a Triune God occupies an important place in the church's life and worship. The church both during the apostolic and the immediate post-apostolic periods lived with the consciousness of worshiping one true God whom the same ecclesial community understood as being present to it and experienced as the Father, the Son and the Holy Spirit. This threefoldness imbued early Christian consciousness of the trinitarian mystery (Farrelly 2005:5). For instance, the apostolic church believed Jesus to be in the form of God (Phlp 2:5-7). He was worshipped as Lord (Phlp 2:9, 11) and the Johannine prologue identifies him as the divine Logos (Jn 1:1, 14). Besides its own experience of the Christ-event that convinced it of the divinity of Jesus, the early church appropriated Old Testament metaphors of Word and Wisdom in its endeavours to have a better understanding of its conception of God who exists in three persons. According to Robert Letham, the Word and Wisdom of God as found in the Old Testament provide, as it were, 'the closest background for the eventual emergence of the doctrine of the Trinity' (Letham 2004:30).
Although primarily used as personifications in the OT, and not as metaphysical principles, the roles of Son and Wisdom, Word and Spirit were very helpful to the early church in fashioning out its notion of a triune God that is characteristically Christian and heavily laden with trinitarian undertones (Letham 2004:32). Passages like Proverbs 8 and 9 and Job 15:7-8; 28:12 make ample use of the Word/Wisdom metaphors in their descriptions of the divine reality. As a matter of fact, the Spirit conceived both as the attribute of God and the power of God at work in the cosmos and in individuals is mentioned about 400 times in the whole of the Old Testament (Letham 2004:29, 30). Given the preponderance of the suffusions about a triune God in the Old Testament, although scattered and not in a coherent and systematic manner, Benjamin B. Warfield states that (cited in Letham 2004:32): 'The OT provides the essential foundation without which the full Christian doctrine of God could not exist. The OT contains, in anticipation, categories used to express and elaborate the Trinity'. Put differently, it means as Robert Letham rightly surmises Letham 2004): The NT and post-NT Christian language for the tripersonal God flowed from the Jewish Scriptures, for though deeply modified in the light of Jesus's life, death and resurrection, naming God as Father, Son and Spirit 'found its roots in the OT'. (p. 32) Christian apologists of the 2nd and 3rd centuries drew inspirations from the Bible and from the then emerging church's liturgical traditions began to develop some form of systematic articulations of trinitarian doctrine. The rudiments of their thoughts and works foreshadowed an advanced and coherent trinitarian theology of their successors in that venture. First among the earliest Christian thinkers is Justin Martyr who during the 2nd century employed Stoic philosophy to make a distinction between Word and the knower. He applied it in his efforts to explain the connection between the Father and his Word. Justin in his apology defended Christians who worshipped a triune God whom they addressed as 'the Most true God, the Father and the Prophetic Spirit' (Farrelly 2005:5;Toom 2007:61). Theophilus of Antioch (flourished c. 180) is another 2nd century Christian apologist who expounded on the Christian triune God in his amalgam of Jewish and Hellenistic thoughts. Theophilus is the first-known Christian writer to use the Greek word Trinity (trias), which he applied to the Godhead in reference to God, Logos and Wisdom (Toom 2007:61;Whittaker 2018). According to Tarmo Toom, the Greek trias as was used by Theophilus denotes 'threeness' but not in the Latin sense of trinitas with the connotation of unitas (unity or oneness). As such, unlike the Latin trinitas, the Greek trias does not carry within itself the creative tension between 'threeness' and 'oneness' as would later be the case when the Latin trinitas was used for the distinct Christian notion of God (Toom 2007:62).
St Irenaeus is another figure within the orbit of the nascent trinitarian thought of the 2nd century. He taught that one God is the creator who became manifest as Father, Son (Word) and Spirit (Wisdom). Irenaeus called both Word and Wisdom 'the two hands of God' (Toom 2007:63). As for Origen in his conception of the divine uni-plurality, the one God did not become established at the incarnation but was rather made manifest at the incarnation. Origen's use of the term hypostasies served to highlight the three divine persons as distinct realities without the connotation of 'personal relations' as the term came to be used much later in the 4th century (Toom 2007:66). By means of Middle Platonism, Origen conceived of the Son and the Spirit as eternal emanations from the Father in comparison to the emanation of light from the sun (Farrelly 2005:5).
When it comes to earlier Latin Christian thinkers, Tertullian and Novatians in the 3rd century occupy the first place for their role in the development of trinitarian theology. Tertullian towards the end of the 2nd century and the beginning of the third, is reputed to be the first Western Christian thinker to use the Latin word trinitas in the sense of capturing both plurality (tres or trias) and unity (unitas). For him, the unity of the Father and the Son is a unity of substance, while their individual distinctions are understood as those of persons (Farrelly 2005:5;Hildebrand 2014:106). As can be found in his work Adversus Praxean 12 (c. 213), Tertullian writes that the Father, Son and Holy Spirit are una substantia in tribus coharentibus (one substance in three coherent [persons]) (cited in Toom 2007:72). His formula of 'one substance in three persons' as well as his use of a psychological analogy to explain the relationship with the Father and the Son prepared the way for the development of trinitarian theology in the West and foreshadowed the thoughts of St Augustine in the same regard (Hildebrand 2014:106). If Tertullian was the first to use the word trinitas, a 3rd century contemporary of his, Novatian around AD 250 became the first Latin Christian author to write a Latin treatise on the Trinity (Toom 2007:72). Novatian's De Trinitate until the 16th century was wrongly passed over to Tertullian as its author. Quite curiously, while Novatian's work bears the title De Trinitate, the author strangely enough never actually used the word trinitas in his treatise (Toom 2007:73). Naturally, as elaborations of trinitarian doctrine were still at their inception stage, the pendulum hovered between the binitarian and trinitarian borders, while awaiting a much clearer trinitarian 'systems' of Christian theology that would come after the end of Christian persecutions in the 4th century (Sanders 2005:45;Toom 2007:65, 73).

A doubled-sided confession of faith
Classical trinitarian theology began with probing into mysterium salutis; even though, as it later became an explicit doctrinal construct, it has its footings in the scriptures (Sanders 2005:45). It was the inquiring attempts of the ancient church about soteriology that laid the foundation for trinitarian and Christological dogmas that became crystallised in creedal formats (Van Wilgenburg 2010:329). Territorially bounded within the two main parts of the Roman Empire around the Mediterranean basin, the church in its two main branches during the post-apostolic era approached the Trinity differently. While the Latin West began with the unity of God (de Deo Uno), the Greek East for its part, started off with the three persons of the Trinity (de Deo Trino) (Drever 2007:235). Lewis Ayres has perceptively observed that the trinitarian propositions of either side of the divide, especially after the Council of Nicaea (325) and Constantinople (381), were framed for the sake of combating heresies on the one hand, and on the other hand, for the sake of safeguarding 'the irreducibility of the divine nature, power, essence, and glory' (Ayres 2007:142). This was also true about 'the irreducibility of the divine persons or hypostases' (Ayres 2007:142). Put differently, the West affirms one substance existing in three persons (their unity), and the East acknowledges three persons in God existing as one substance (differences of their persons).
It is within the given context that traditional trinitarian theological formulation of the Father-Son-and-Spirit, and the Father's monarchia, was understood (Ayres 2007:142). As far as the West is concerned, preservation of the oneness of God permits it to proceed in consideration of the being of the Godhead where the Father is the Father because he begets the Son. He subsists in relation to the Son and the Spirit. Employing their subsisting relations, the West affirms the distinct identities and oneness of the three divine persons. On the flip side, traditional Eastern trinitarian theology believes that the Father is the sole source of the Son and the Spirit. This conceptual difference would be the centre of the filioque controversy when it first reared its head in the 7th century and began to be exacerbated in the following century with the contention of the Frankish church under Charlemagne and his imperial aspiration in rivalry with the Byzantine emperor in Constantinople (Felmy 2014:213). In relation to the Son, the Father is ungenerated, while in relation to the Father, the Son is generated or begotten. And in relation to both the Father and Son, the Spirit proceeds from the Father alone. This is beautifully interlaced by John of Damascus in this manner: 'The Father, the Son and the Holy Spirit are one in all respects, save those of not being begotten, of birth and of procession' (cited in Letham 2004:241). Reframed somewhat differently: 'All then that the Son and the Spirit have is from the Father, even their very being' (cited in Letham 2004:241). Evidently, the unity of the Trinity is located in the Father, who is the fount of the divine processions, and in the intimate inter-relatedness of the three divine persons through their mutual co-inherence (Weinandy 1995:6-7). The theological differences between the West and the East go beyond mere emphases. Those differences also concern conceptual contrasts in their understanding of the Trinity. Nevertheless, it may be safely assumed that the two halves of the ancient church consider the Trinity as a fundamental Christian article of faith. Of crucial importance is the accompanying two rules that characterised classical trinitarian theology. One rule ensures that the 'outer-Trinitarian' works are understood as the works of the three divine persons. The second rule guarantees that the three divine persons are carefully distinguished in 'inner Trinity' (Helmer 2003:143). It serves to ensure that persons of the Trinity are individually recognised with their peculiarity so that the Father is not taken to be the Son, and the Holy Spirit is not confused with the Father or the Son.
Naturally and expectedly, each of the two sister churches had its own theological luminaries, even though the Latin West unlike the Greek East also lays claim to the Eastern Fathers. For instance, Athanasius of Alexandria is venerated as a saint and doctor ecclesiae in the Roman Catholic tradition. In addition, he is accorded the honour of being the protagonist of orthodoxy regarding the Trinity and Christology (Van Wilgenburg 2010:337). With peculiar nuances, Athanasius, Augustine, the Cappadocians (Basil the Great, Gregory of Nazianzus and Gregory of Nyssa) as well as John Chrysostom made significant contributions to classical trinitarian orthodoxy (O'Collins 2002:363). Pointedly, trinitarian theology of both West and East is founded upon the Nicene-Constantinopolitan Creed alongside the Quicumque Vult. The Quicumque is popularly known as the Athanasian Creed because it is traditionally attributed to him. That the authorship of the document does not belong to Athanasius is no longer in doubt as internal evidence shows that it contains issues and controversies that did not yet exist at the time of the Alexandrian bishop. For instance, according to Karl C. Felmy, the Filioque clause is found for the first time in Quicumque, which may indicate that the document may have emerged almost at the same time and from the same geographical provenance as the controversial clause (Felmy 2014:213). It is now generally accepted that the Quicumque is characteristically western. It is most likely to have originated from an Augustinian school of thought somewhere in Spain because of its unmistakeable similarity to the thought pattern of the bishop of Hippo (Felmy 2014:213). In the postulation of Siecienski (2015:10), the document may have been written between late 5th and early 6th centuries. And specifically, to the creed, without the addition made at the Council of Constantinople in 381, the Nicene Creed appears to be the first formal conciliar statement on the Trinity.
Although the pope was represented by two presbyters at the Council of Nicaea that was convoked by Emperor Constantine, Western theologians were somewhat not immediately and directly involved in the controversies that ensued in the East especially after the close of the Nicene Council. As Jörg Ulrich has demonstrated, the Nicene Creed may not have been well known in the West until about towards the end of the AD 350s. He cites the example of Hilary of Poitiers, who acknowledged that he had never heard of the Nicene Creed. Hillary only became better informed of the Creed during his exile in the East around 356 (Ulrich 1997:20). Upon his return from exile, Hilary became one of the prominent persons to popularise Nicaea, its creed and theology in the West. Ulrich opines that it took almost 40 years (i.e. well into the sixties of the 4th century) for Latinspeaking theologians to wade into the theological debates of the post-Nicene period. Prior to Hilary, Athanasius and Marcellus of Ancyra had taken refuge in the West after their depositions by bishops who were loyal to Emperor Constantius II. While Marcellus was ousted from Ancyra for dogmatic reasons, Athanasius was exiled from Alexandria for ecclesiastical and political reasons (Ulrich 1997:16, 21).
In his declaration of orthodoxy before the Roman Synod in 340, Marcellus placed emphasis on the unity of the Trinity in his interpretation of the Nicene Creed. Athanasius also participated at the same synod that was convoked by Pope Julius I. For his defence, Marcellus argued against 'those who teach that the Son is a different hypostasis' while insisting simultaneously on the relation between the Father and the Son as being of 'one substance' (Ulrich 1997:18). Marcellus appeared to have succeeded in Rome on two grounds. On the face value, Marcellus's version seemed plausible as the correct and orthodox doctrine of the Trinity. The reason is not all that far-fetched because the Nicene creed at the time was not widely circulated in the western part of the empire. It was rather the Apostles Creed that was mostly in use in Rome and other places in the West. The second is the close similarity between the trinitarian conception of Marcellus and Tertullian who had used the term una substantia to describe the Trinity. Both Ulrich and Joseph O'Leary observed in unison that Tertullian in his Adversus Praxean written around AD 214 had described the trinitarian faith as a major distinctive stamp that distinguished Christianity from Judaism (O'Leary 2014:240;Ulrich 1997:18). Hence, through the use of skilful polemics against his enemies in the east, Marcellus portrayed Eastern Origenists as tainted with http://www.ve.org.za Open Access Arianism on account of their supposed doctrine of 'hypostases'. With trinitarian terminologies still very much unclear at their incipient, the West was persuaded by Marcellus especially against the background of an earlier 3rd century heresy of 'three substances' (Ulrich 1997:18 Western trinitarian theology after its tutelage under the shadows of Athanasius and Marcellus of Ancyra can be said to have taken roots and acquired its distinctive characteristics during the patristic golden period through the works of Latin luminaries like Gaius Marius Victorinus, Ambrose of Milan and Augustine of Hippo. After Augustine, the West increasingly followed his psychological model of trinitarian theology and his trinitarian orientation that moved towards the doctrine double processions of the Holy Spirit from the Father and the Son (ex Patre Filioque) (Felmy 2014:212). On the opposing side, a similar assertion can also be made about Eastern trinitarian theology that carries the lasting seal of the Cappadocian Fathers. They conceived the Father within the Godhead as the unifying reference for the Son and the Spirit (Rostock 2010:323). They also made a clear distinction between unity and ontological oneness of the three divine persons. Alongside other Greek Fathers like John Chrysostom, the trinitarian theology of the Cappadocians occupies a prominent place in the Orthodox Church. The same is true of John of Damascus whose rejection of the filioque is couched with Eastern traditional trinitarian theology, which unambiguously places the emphasis on God's unity. And only thereafter, it proceeds to affirm that the Son and the Spirit are established on the same principle, which is the Father himself (Felmy 2014:214). As explicated by Nigel Rostock, John Zizioulas (one of the most contemporary influential Orthodox scholars) sustains the view that it was the Greek Fathers that correctly identified the unity of God within the person of the Father, rather than in the one ousia (Rostock 2010:323-324). As for Timothy Ware: 'According to the Greek Fathers of the fourth century, whom the Orthodox Church follows to this day, the Father is the sole and ground of unity in the Godhead' (cited in Rostock 2010:324).
In the explication of Thomas Weinandy, the Cappadocians were the first to introduce the concept of 'cause' into the being of God whereby 'what causes God to be is the Person of the Father, not the one divine substance' (Weinandy 2002:409). However, they 'did not fully grasp Athanasius's insight into Nicaea's homoousion doctrine' and its metaphysical import because their understanding of the Trinity was enunciated from an Origenist spectrum (Weinandy 2002:410). Theirs is a conception of the Trinity that is linear such that the Son and the Holy Spirit derive their divinity from the divine nature of the Father (Weinandy 2002:410). On account of their lack of metaphysical acumen like Athanasius, the Cappadocians unwittingly impressed Platonic emanationism upon Orthodox trinitarian thought, which in the words of Weinandy (1995:13) 'is present to this day'. Nevertheless, it is worth acknowledging that it was the Cappadocians, who thoroughly developed the concept of hypostasis. By so doing, they gave greater priority to the divine persons over abstract divine nature (Meyer 2005:238). It can be safely deduced that while Middle and Neo-Platonism had an influence on the East's linear conception of the Trinity, Aristotelian epistemology played a similar role in shaping Western trinitarian theology (Weinandy 1995:10, 13-14). This divergence between East and West regarding their respective trinitarian theologies was almost established long before the filioque controversy made its debut around the middle of the 7th century. It is most likely that the first case in reference to the filioque was mentioned between AD 645 and 646 by Maximus the Confessor in his Letter to Marius during the time of Pope Theodore I (AD 642-649) (Siecienski 2015:10).
Of historical significance is the fact that the West and East owing to their geographical, cultural and linguistic differences, the two sister churches disagreed on a number of issues. For instance, they disagreed on the question of jurisdictions, especially the pretention of superiority of the Roman church and papal authority, whether leavened or unleavened bread should be in the Eucharist as clerical celibacy and marriage. It can, therefore, safely be affirmed that the filioque clause and the quarrels around were only a cementing of those series of disagreements between East and West (Letham 2004:201). It must be recalled that filioque was adopted by the third synod of Toledo in 589 and imposed anathema on anyone who did not acknowledge the Holy Spirit proceeded from the Father and the Son. The background of the synodal adoption was provided by the second synod of Toledo (c. 527/531). Under the influence the Visigoth Arian kings Reccared and his father Leovigild, that synod wilfully omitted an aspect of the doctrine about the Holy Spirit proceeding from the Father and from the Son (Felmy 2014:213). When the issue resurfaced later in the 8th century with Charlemagne and his Frankish court theologians against the profession of faith of Nicaea II (787) (Farrelly 2005:103). It is fair to note that the West initially did not exert itself in defence of the clause because it was never used in Roman liturgy until 1014 during the pontificate of Benedict VIII (1012-1024) and at the insistence of Emperor Henry II for his coronation Mass in Rome (Farrelly 2005:102). The Fourth Lateran Council (1215) only mentioned it in number 1 of its confession of faith in relation to the Holy Spirit where it acknowledged that the Spirit proceeds 'from both equally' (cited in Tanner 2020). It was proclaimed a dogma of faith in 1274 at the Second Council of Lyons (Letham 2004:202).

Medieval trinitarian intuition
John Damascene (c. 675/6-749) in the East is generally considered as having summed up the patristic trinitarian thought in a way that has become normative for the Eastern churches. Augustine (354-430) of Hippo achieved a similar feat for the Latin West in its conception of the Trinity. His theology later became much more intensified through the writings of Anselm of Canterbury (Kasper 1986:298) and through the optics of medieval perception of theology as faith-seeking 'scientific' understanding (fides quaerens intellectum scientificum) (O'Collins 2014:4). The intervention of Augustine in clarifying the mystery of the Trinity as well as the key concepts and terminologies associated with the doctrine has remained indelible in the annals of Western theology. Among his lauded merits is his clear distinction between trinitarian identity and relations. According to Augustine, while the three Divine Persons are One at the level of essence and absolute perfection, they remain distinguished at the level of relations (Mondin 1996a:403). In other words, the identity of the Father is paternity, that of the Son is filiation, while that of the Spirit is spiration (passive donation between the Father and the Son) (Mondin 1996a:403-404). John Damascene's De Fide Orthodoxa is strategically important for the East as Augustine's De Trinitate is for the West. In comparison, Damascene developed a trinitarian theology that is biblical and doxological oriented, while Augustine's great achievement lays in his emphasis on the activity of the trinitarian persons, which he conceives of as flowing from their inseparable unity. His achievement is also predicated upon his concept of person to explain the difference in the sending of the Son and in the sending of the Spirit (Letham 2004:200).
Considered from the standpoint of Augustine, it simply means that the names of the three divine persons of the Trinity denote relations (Weinandy 2002:412). Another insight of Augustine, as gleaned from De Trinitate, is the preferred analogy of the mind to describe the Trinity. In classical philosophy, the mind consists of three faculties: memory, intellect and will. Although all three are distinct in their various functions, they constitute one unique substance (Drever 2007:237;Mondin 1996a:404). Transposed to trinitarian theology, it becomes common place to '… find in Augustine such statements as: the Trinity is the one true God, or God is the Trinity' (cited in Kasper 1986:262). Another dimension of the Augustinian notion is a trinitarian theology that is rooted in a perception of the historical missions of the Son and the Spirit (O'Leary 2014:238). The trinitarian missions go beyond opera ad extra because they also manifest the eternal processions of the Son and the Spirit in human history. In reference to the mission of the Son, Augustine writes in De Trinitate IV: 29: 'Just as to be born is for the Son to be from the Father, so to be sent is for the Son to be known that he is from him' (cited in O'Leary 2014:237).
Although Augustinian 'essentialist' view was the dominant trinitarian perspective in the West during the Medieval era, it was, however, not the only perception or notion of the Trinity. There emerged on medieval theological scene the 'personalist' tradition, particularly with the coming of the Mendicant orders, and more specifically, the Franciscan friars. According to Walter Kasper, the adoption of the 'personalist' notion of the Trinity predated the Franciscans because someone like Hilary of Poitiers in the second half of the 4th century had already made use of it in his trinitarian theology (Kasper 1986:298). In the opinion of Kasper (1986:298), the Latin 'personalists' took as their own the same trinitarian concern of the Greek fathers, which is summed up in the 'monarchy of the Father'. It gained prominence in the Middle Ages through the work of William of St Thierry, followed by Richard of St Victor who became its most important exponent. Richard of St Victor was one of the influential authors who wrote one of the most important treatises on the Trinity between Augustine and Thomas Aquinas. He preceded Bonaventure in anchoring trinitarian relations and trinitarian persons within the frame of love and made the connection between love and the good (Wawrykow 2014:189). Another outstanding figure in the 'personalist' tradition was Alexander of Hales who continued the trinitarian thought of Richard of St Victor. Alexander of Hales was a Franciscan friar who had a considerable influence on another Franciscan confrere of his, in the person of St Bonaventure (1221-1274) who revered him as his spiritual master (Mondin 1996b:263). In a typical Franciscan understanding of emanation, Hales makes a distinction between two kinds of emanation in reference to the Son and the Spirit: per modum naturae and per modum liberalitatis (Wawrykow 2014:189).
As the initiator of the Franciscan theological school of thought, Alexander of Hales impressed upon it a sapential/ affective character, which eventually became one of its distinctive marks. Other peculiar characters of the Franciscan school include illumination and recourse to exemplarism in explaining that knowledge is based on the perception of exemplars as existing in the mind of God. His disciple Bonaventure would later make use of 'per modum exemplaritatis' to depict the Trinity as the archetype, the first and supreme model of all things (Mondin 1996b:303). As for the final objective of theology, Alexander understood it as having an affective cum contemplative rather than a speculative scope for its natural and final goal. In his theological treatise and exposition on the Trinity, Alexander came up with an 'integral theology of love' by means of which he explained the dynamism of the divine processions of the Trinity. Alexander did not rely on intelligence to distinguish the double trinitarian procession because intelligence may not produce another being. He argued that only love is given from one person to another, and therefore, only love is the appropriate principle to explain the Trinity. It means that the Son is begotten in the Father's loving self-giving, which is the love that the Son returns and shares with the Father. And within the optics of Western trinitarian theology, the Holy Spirit is conceived as the fruit of that mutual love between the Father and the Son (Wawrykow 2014:187). It is in this vein that Alexander positioned himself as the continuator of the intuition of Richard of St Victor who maintained that there is a plurality of subjects in the Supreme Love (Mondin 1996b:262-263).
As for Bonaventure, called 'the Seraphic Doctor' in his own right as one of the great medieval thinkers, his theology can be described as a profound meditation on the Trinity. He was one of the first medieval Latin theologians to employ the term circumincessio in his trinitarian theology (Mondin 1996b:303). It is the Latin translation of the Greek perichoresis, used by the Greek fathers, notably by John Damascene to explain the mutual indwelling of the three divine persons without mixture. It suggests that the unity of the Trinity lies in the fact that no one of the three divine persons can be thought of without the other two, as each of the three divine persons is co-present to one another. According to Bonaventure borrowed from Augustine the contemplation of 11 'highest nobilities (nobilitates) of the divine being: life, sensitivity, intelligence, immortality, power, justice, goodness, incorruptibility, immutability, incorporeity and beatitude' (Mondin 1996b:303). He reduced the nobilitates from 11 to 3, namely, eternity, wisdom and beatitude. Bonaventure went further and finally reduced all three 'highest nobilities' to only one: wisdom or knowledge. In applying it to the Trinity, he identified the generating Mind as the Father, the generated Word as the Son, and Love as the Holy Spirit. In contrast to Augustine, Bonaventure depicts the Spirit as the active unifier in the act of love because he is the unitary knot between the Father and the Son (Mondin 1996b:303). Accordingly, as it pertains to the nature of the good to diffuse itself, the Father's loved is shared with the Son as the beloved and the Spirit becomes the co-beloved of the Father and the Son. Bonaventure uses emanation as an eternal act to explain the origin or source of the three persons. For the Seraphic doctor, all that belongs to the Father in his divinity except paternity is given to the Son, while that belongs to the Father and Son as divine persons, apart from paternity and filiation, is communicated to the Holy Spirit in terms of active spiration while passive spiration belongs properly to the Spirit (Friedman 2014:198;Wawrykow 2014:187).

Medieval trinitarian thought reached its zenith in Thomas
Aquinas. As Joseph Wawrykow asserts, the distinctive mark of Aquinas's trinitarian theology is his emphasis on God's salvific intention of God, which in the mindset of Aquinas is the beginning and end of any reflection on the Trinity (Wawrykow 2014:193). Aquinas possessed an uncommon ability for synthesis that enabled him to find an equilibrium between the various conceptions of the Trinity (Kasper 1986:298

In making a distinction between De Deo Uno [the one God] and
De DeoTrino [the triune God], Aquinas makes room for the unity and diversity of the three divine persons (Letham 2002:29). On the one hand, their relationships define their unique identities as ontological subjects or persons, and on the other hand, it defines their ontological unity as the one God. This is possible because the three Divine Persons subsist as who they are in relation to one another, for together they 'form a dynamic ontological communion of love' (Weinandy 2002:413). Thomas's synthesis of the 'essentialist' and 'personalist' notions is shown in the insistence that the divine persons of the Trinity are subsistent relations. Within that order, paternity belongs to the Father as the unbegotten or ungenerated, filiation to the Son as the generated and passive spiration to the Spirit in relation to the active spiration of the Father and the Son. As far as Aquinas is concerned, the four relations in the Trinity (paternity, filiation, spiration and procession) help to distinguish the three persons (Mondin 1996b:376-377;Wawrykow 2014:193). Aquinas conceives trinitarian processions as occurring per modum intellectus and per modu mamoris (O'Leary 2014:230). It can be assumed that by depicting the Spirit as the reciprocal Love and Gift between the Father and the Son and as proceeding through the common volition of the Father and the Son, Aquinas seeks to blur the sharp edges of the somewhat abstract essentialist perspective of the Trinity. Like Augustine, he designates the Holy Spirit as the mutual love or gift shared and given by the Father and the Son (Weinandy 1995:8-9). Perhaps, it may also be reflective of the medieval rule of necessity, which implies that only the relations in the divine essence are necessary (Helmer 2003:131;Mondin 1996b:376).
The medieval church appears to have sanctioned the two prevalent notions of the Trinity of the epoch, which was noticeable in the Franciscan and Dominican positions or approaches. Following the footsteps of Thomas Aquinas, the Dominican favoured the idea that the personal properties of the three persons of the Trinity are relations. The Franciscan tradition focused its attention on trinitarian emanation, which describes how the three divine persons originated because they share the same divine essence (Friedman 2014:198). Instructively, as observed by John Farrelly, the interventions of the church's magisterium on trinitarian discussions aimed at the careful balancing of trinitarian unity and distinctions (Farrelly 2005:104). It is helpful in this regard to recall the tres res trinitarian terminology of the Fourth Lateran Council in 1215. Prior to Lateran IV, the Synod of Soissons (1092) had condemned tritheism that was ascribed to the monk Roscelin. The Council of Rheims (1148) equally disapproved of the distinction that was being made between the persons of the Trinity and their divine essence (Farrelly 2005:104). As for explication of Lateran IV, the tres res or tres personae are metaphysically constituted by duo res: one res as the relation and the second res as the essential (Helmer 2003:137). The immediate background of the council's tres res terminology was provided by the council's condemnation of 'Joachim of Fiore's conception of the divine unity as nothing more cohesive than a unity of collection among the persons' (Iribarren 2002:292). The conciliar trinitarian terminology was an endorsement of the thought of Peter Lombard whom Joachim of Fiore had accused of introducing 'quarternarism' in the Trinity. According to Isabel Iribarren, 'quarternarism' implied a realist understanding of the four divine relations. With regard to 'quarternarism', attempt to posit a real distinction between divine relations and the divine essence was construed as introducing a quarternity of four 'relative things' into the being of God. Therefore, by endorsing the trinitarian theology of Peter Lombard, Lateran IV absolved him of 'quarternarism'. The council went further to pronounce a dogmatic statement on the Trinity in this manner (cited in Iribarren 2002): here exists a certain supreme reality …, which truly is the Father and the Son and the Holy Spirit, the three persons together and each one of them separately. Therefore in God there is only a Trinity, not a quaternity, since each of the three persons is that reality … This reality neither begets nor is begotten nor proceeds. (p. 292) Medieval trinitarian theological thoughts reached their apex in 1215 at the Fourth Lateran Council and at the Second Council of Lyons in 1274. Both councils formally sanctioned the teachings of medieval theologians, which the Latin church judged as orthodox. In contemporary terms that official sanctioning may be called 'theology from above'. Both councils set the formula such as the proposition, tres res suntuna res (Helmer 2003:128) and also established the parameter and the general terms for the trinitarian discourse that remained operative in subsequent centuries. Even at the initial stage of the Reformation, a leading figure like Martin Luther did not entirely repudiate medieval trinitarian intuition and discourse. This is evident in a hymn by Luther, 'Dear Christians, one and all rejoice'. It was inspired by this scriptural verse: 'The Father has sent His Son as the Saviour of the world' (1 Jn 4:14) (Helmer 2003:140). Although the conciliar position and parameters provided a rich ground for the plurality of trinitarian reflections, they equally established the theological structures and trinitarian yardsticks or frames of reference by means of which the Western Church scrutinised trinitarian orthodoxies. It was through the instrumentality of those conciliar trinitarian norms that some medieval scholars were judged, such as Peter John Olivi, Meister Eckhart, John of Pouilly and the nominalist tradition of William of Ockham and John Duns Scotus (Helmer 2003:130;Iribarren 2002:290). Duns Scotus (1265-1308) is considered as one of the great theological minds of the medieval time. His reformulation of the Franciscan trinitarian tradition was one of the major references for trinitarian discourse and debate for most of the 14th century (Friedman 2014:202). He rejected the theory of relation as constitutive of the divine persons while on the contrary, he affirmed that the divine persons are absolutes, which according to him means that they are constituted by origin. The absoluteness of the devine persons as the keystone of Scotus's thought on the Trinity was based on his understanding that emanations within the Trinity were the major sources of the distinction of the three divine persons. In his postulation, the Son is not the Father and not the Holy Spirit because he emanates naturally from the Father by way of intellect. The Spirit, in turn, is neither the Father nor the Son because he emanates by way of will (Friedman 2014:202-204).
Another aspect of medieval trinitarian theology is the filioque controversy that has caused the estrangement between Western and Eastern churches. The attempts that were made towards union at the Second Council of Lyons in 1274 and the orchestrated Laetantur Coeli (decree of union, 06 July 1439) at the Council of Florence proved incapable of healing the centuries-old division. Lyons II upheld the legitimacy of the addition on the following ground: the Spirit proceeds not from two principles but from the Father and the Son as one co-principle (Dulles 1995:32-33). The Council of Florence, for its part, duly recognised the Eastern and Western versions of the creed as equivalent. It admitted the legitimacy of the two versions for use in the two respective churches. Despite some musings about possible rapprochement, the Catholic Church in the West has retained the 'offending clause' as an indispensable part of its understanding and profession of the Nicene-Constantinopolitan Creed. According to Dulles (1995:35), from the viewpoint of the Roman Catholic Church, it is reasonable to concede that after many centuries of its use, there is no doubt that filioque has attained in the church the status of an irreversible ecclesiastical dogma.
There has been some modest progress on the matter especially in recent times albeit not conclusive. One concrete example is the official 'clarification' published in 1995 by the Pontifical Council for Promoting Christian Unity It equally restates the positions of both sister churches in this manner: The Greek Fathers and the whole Christian Orient speak, in this regard, of the 'Father's monarchy', and the Western tradition, following St Augustine, also confesses that the Holy Spirit takes his origin from the Father 'principaliter', that is, as principle (DeTrinitate XV, 25, 47, PL 42, 1094-1095. In this sense, therefore, the two traditions recognize that the 'monarchy of the Father' implies that the Father is the sole Trinitarian Cause (Aitia) or principle (principium) of the Son and of the Holy Spirit. (n.p.) In a response to the Vatican document on behalf of the Orthodox Church, Metropolitan John Zizioulas of Pergamon acknowledged the positive development and the friendly nature of the language used in the document. However, he let it be known that certain questions remained unresolved and among them is this key question: 'Does the expression "principaliter" necessarily preclude making the Son a kind of secondary cause in the ontological emergence of the Spirit?' (Zizioulas 1995). Therefore, according to Zizioulas (1995), that stumbling block ought to be properly clarified because the East and West do not understand 'principaliter' in this way: It is extremely important, in my judgment, to clarify the point concerning the 'source' (πηγή) or 'principle' or 'cause' (αιτία) in the Holy Trinity. This is crucial perhaps decisive. The document of the Vatican sees no difference between the monarchia of the Father, i.e. the idea that the Father is the sole 'principle' in God's Trinitarian being, an idea strongly promoted by the Greek Fathers, and St. Augustine's expression that the Holy Spirit proceeds from the Father 'principaliter …'.
Notwithstanding the lingering misunderstanding that remains, scholars see the positive approach and attitude displayed by Rome and Constantinople manifested in their willingness to continue theological consultations and dialogue, as already a good progress in the ecumenical project. Someone like David Guretzki interprets it as 'the spirit of irenicism' has been prevalent in 'both ecclesiastical and scholarly dialogue on the filioque in the past few decades …' (Guretzki 2015:42-43).

From conceptualist to historyrooted
By and large, the constitutive elements of Roman Catholic doctrine of the Trinity reached their present phase with the official approval of the church in successive epochs. The councils of the Latin Church and the popes drew upon the works of theologians whose insights and contributions were adjudged orthodox and attuned with the official creed. In the actual state of trinitarian theology, it is taken as beyond question that traditional understanding of the Trinity underscores the point that there are four relations in God: paternity, filiation, active and passive spiration. It acknowledges that the three divine persons of the Trinity are identical with one another in all things although differing about relations of origin. For instance, Fatherhood is not Sonship, just as active and passive spirations are distinct and unique in themselves (Dulles 1995:36). Considered as causa finita, contemporary trinitarian theology in its diversity delves into immanent and economic Trinity, social trinitarianism and trinitarian missions. It also considers the question of how the Trinity may be viewed either through the conceptualist approach or the historical model of revelation. All these areas of concerns are not only reflective of the evolution of events and change of scopes that have taken place over time, they are also indicative of the quest for theological relevance or the concretisation of doctrines into real-life issues. In some ways, the focus of trinitarian theological concerns has increasingly moved away from metaphysics to anthropology, brought about particularly by the Enlightenment and its attention from above to below, that is, from God to the world. Instructive in this sense is the clarion call from Alexander Pope: 'Know then thyself, presume not God to scan, the proper study of mankind is man' (cited in Letham 2002:30).
The distinction between immanent and economic Trinity is one of the characteristics of contemporary discourse on the Trinity where attention has been increasingly focused on the historical approach to church doctrines. Within that prism, human experience is understood as a privileged locus of revelation because it is comprehended as an inevitable medium through which divine self-manifestation takes place (O'Collins 2002:365). In the same frame of thought, the church's doctrine about the Trinity is not conceived as a water-tight transmission of revealed truth. As opined by McDermott (2012) And as for the terms trinitas oeconomica and trinitas essentialis, according to Helmer (2003:131), they were first used by Johann Urlsperger within the context of transcendental philosophy in the late 18th century. As borrowed terminologies, they were employed in trinitarian theology to denote two modern possibilities of trinitarian conceptualisations, namely Kantian and Hegelian. In the first pole, that is the Kantian paradigm, it starts from the divine economy to immanent Trinity. On the opposite pole, the Hegelian paradigm explores logically and ontologically the unfolding of the immanent into the economic Trinity (Helmer 2003:131). Although both paradigms still lurk in the background in trinitarian discourses, contemporary theologians are more likely to direct their focus towards the missions of the Trinity instead of inner-trinitarian processions (McDermott 2012:113).
One way to gauge the evolution that took place in Catholic theology between the late 19th and 20th centuries is to look at the progression from the First Vatican Council (1869-1870) to the Second Vatican Council (1962)(1963)(1964)(1965). Both councils approached the Trinity quite differently. The First Vatican Council tended towards being conceptualist in its understanding of the mystery of Trinity as part of the revealed truth of the Christian faith. It maintained the balance by insisting that the Trinity is not alone but also by reason known through supernatural revelation. This much is visible in its dogmatic constitution Dei filius (On the Catholic faith).
Although the second part of the schema that was exclusively devoted to the Trinity, creation and exaltation never came up again for discussion because of the abrupt suspension of the council, yet allusions to the oneness of God were quite evident. In its profession of faith, the council confessed God 'as one, true and living … he is one, unique, spiritual substance, entirely simple and unchangeable, distinct from the world in existence and essence …' (Denzinger 3001-3002). Aware of the thorny debate of the time on faith and reason, the council saw the Trinity as belonging to the truths of faith, which it declared to be supernatural. It is, therefore, part of the 'mysteries hidden in God which cannot be known unless divinely revealed' and even so, not completely understood when revealed, 'for divine mysteries by their very nature so exceed the created intellect …' (Denzinger 3015-3016  (Nichols 2014:287).
In tandem with the new thought that had already begun in the preceding century and gained motion after Jules Lebreton's Histoire du dogme de la Trinité (1903), the pendulum of trinitarian thought appeared to have swung towards history and human experience (Holzer 2014:323). It signalled the beginning of the renewal of positive theology, which owes a lot to historical theology that places emphasis on the historical development of doctrines and developments of trinitarian theology in different traditions. Contemporary Catholic theology is, therefore, a beneficiary of the change of focus and a widen horizon that came with positive and historical theology (Holzer 2014:323-324). This much was quite evident at the Second Vatican Council. In its dogmatic constitution on Divine Revelation, Dei Verbum, the council accepts that the trinitarian faith is historically rooted in the words and deeds of Jesus Christ. Human experience is understood as an important medium by means of which divine self-manifestation takes place (Denzinger 4202). In Lumen Gentium 4, the origin of the church itself is linked to the Trinity where it says that the Church is described as a 'people brought into unity from the unity of the Father, the Son and the Holy Spirit' (as cited in Farrelly 2005:9). According to Vincent Holzer, it is in ecclesiology that Catholic trinitarian theology finds its important fecundity by situating the Church within the very framework of the economy of salvation because the church is understood as proceeding from the Trinity and equally returns to the same Trinity (Holzer 2014:325). Another great insight of contemporary theology is the rediscovery of the important role of the Holy Spirit as can be gleaned from documents of Vatican II. The council in its 16 documents made overwhelming references to Holy Spirit about 258 times and essentially referring to the Holy Spirit in the definition of the Church and in the renewal of the sacraments (Farrelly 2005:9). This is not surprising in consideration of the fact that someone like Yves-Marie Congar was one of the council's periti who authored a three-volume work on the Holy Spirit (Holzer 2014:325). Another important feature is the trinitarian reading of creation. In the affirmation of Holzer, finding the connection between Trinity and creation is one of the masterpieces of contemporary Catholic trinitarian theology (Holzer 2014:324 The significant shift both before and after Vatican II and during the council, and even afterwards, is an indication of the tension in Catholic theology, particularly between Thomism and Nouvelle Théologie during the first half of the 20th century. It may be described as a tension between 'Conclusion' or 'Denzinger theology' and theological Ressourcement (Schelkens, Dick & Schelkens 2013:122-123). Almost like a theology that was born out of protest to a dominant theological tradition that owed its existence mostly to a single medieval theologian, Nouvelle théologie was resolved to return to the historical roots of Christian theology. It accorded a prominent place to the Bible, liturgy and Church Fathers (Schelkens et al. 2013:125 (Schelkens et al. 2013:125-126).
Generally, as already observed, one of the most visible aspects of Catholic theology in the 20th century is the greater appreciation of historical development of doctrine and patristic studies. As a result, there has been a rediscovery of the Eastern Church Fathers by Catholic theologians, which means that Western theology has benefited immensely in broadening its theological viewpoints. For this reason, as Weinandy has observed, Western theology has come to claim as its own the whole of Christian theological tradition that embraces the East and West (Weinandy 2002:413). As both patristic and scholastic theology seemed to have focused much attention on the divinity of Christ in relation to the Trinity, 20th-century theologians like Rahner and Balthsar paid more attention to his humanity so that Christology can be depicted as the key to unlock their trinitarian thoughts. In the estimation of Rahner, Christology provides the centre of the Christian mystery, and as such, it is within the context of Rahner's trinitarian theology that his Christology takes its definitive contours (McDermott 1986:106). Similar supposition is also true of Balthasar who, on the basis of his Christology, proposes a new interpretation of the Trinity. In Balthasar's view, the Father is the source of life and his hypostasis as Father consists in the total giving of himself to the Son who in turn responds totally and unreservedly, and the Holy Spirit is identified as the very fecundity of divine love in the Trinity (Mondin 1996c:521, 554). Undoubtedly, his greatest contribution is the concept of 'theodramatic' with inspiration from the Pauline doctrine of salvation through the Cross (Holzer 2014:315).
Connected with trends towards humanising a too abstract trinitarian discourse is social trinitarian theology in the footsteps of Jürgen Moltman, Balthasar, John Zizioulas and Sergii Bulgakov. Social trinitarian theologians equally make appeal to Rahner's maxim: 'the economic Trinity is the immanent Trinity and vice versa' (O'Leary 2014:230-234).
While not discarding the trinitarian sobriety of the Church Fathers and the councils, social trinitarianism of the decades of the 1980s and the 1990s exerted much energy and concentration on the inner life of the Trinity and the relevance of God's action in human history. One of the criticisms against social trinitarianism is its overtly reliance on Hegelianism. In the critical summation of Joseph O'Leary, with reference to socialism trinitarianism, he considers it an inadequate tool to expatiate upon the Trinity as the very core doctrine of the Christian faith. In the judgement of O'Leary (2014): The ambition to build the tower of metaphysical theology higher than Aquinas, with the aid of Hegel and Schelling, is misguided; the sole function of the doctrine, as a Schutzlehre (Brunner), is to preserve the biblical experience of God as Trinity. (p. 239)

Conclusion
In keeping with the Latin axiom, lexcredendi, lexorandi, the Western Church considers liturgy as a fundamental expression of the Christian faith. It is one of the major barometers to measure the orthodoxy of trinitarian theological discourse because the 'law of prayer determines the law of belief'. Liturgy is the source of trinitarian theology because it provided the earliest setting for the Christian community to express and live its faith in the Trinity. It has continued to play that role for Western and Eastern churches that are creedal churches, especially when they gather 'In the name of the Father, and of the Son and of the Holy Spirit'. Evidently, the Trinity has also been the subject of fierce theological debates and disputes as well as heightened tensions and critical reflections. As sagely surmised by Bernard Lonergan: `The Trinity is a matter of five notions or properties, four relations, three persons, two processions, one substance or nature, and no understanding' (cited in Letham 2004:1).
The overall aim of this excursus has been to make as concisely as possible a historical exposé of trinitarian theological discourse from the perspective of Roman Catholic tradition and heritage. Given the vastness of the trinitarian doctrine in the Christian argot, this article has limited its focus on the Trinity as one of the basic tenets of the apostolic faith to which both the western and eastern churches subscribe. However, by considering the trinitarian thoughts of Latin theologians, particularly, in the medieval era, it has identified distinctive aspects of Catholic trinitarian theology in terms of emphasis and nuances. This is done in the realisation of the fact that the Church Fathers in both East and West, regardless of differences as imposed on them by language, cultural and philosophical world views, never thought themselves as expounding a totally different trinitarian theology in the strict sense of the term. It is a realisation or discovery that has greatly enriched trinitarian theology and discourse in contemporary Roman Catholicism, especially in the areas of ecclesiology, pneumatology and the place of the Trinity in relation to ecology.