The Nicene Creed's incarnational Trinitarian roots

Making frequent reference to The Trinitarian Faith by Thomas F. Torrance, this article explores the incarnational Trinitarian roots of the Nicene-Constantinopolitan Creed (commonly called the Nicene Creed). To download a copy in Word, click here. For a video about the Creed, click here.

Greek philosophy and the Arian controversy
As Thomas F. Torrance (hereinafter referred to as TFT) notes in The Trinitarian Faith, the Nicene Creed is the work of the Greek-speaking early church fathers in their efforts to carefully express the crucial points of the Gospel where it was being seriously misrepresented under the influence of a dualistic Greek (Hellenized) philosophy. That philosophy posited that God, being one, perfect and unchangeable, must, necessarily, be separate from and have nothing to do with physical matter (including flawed human beings). Influenced by this philosophy, some Christians, including influential leaders, were reasoning that in order to remain aloof from the flawed, changing world of matter, God created angels who created and then interacted with the physical world (thus keeping God at arm's length from the world). In like manner, they reasoned that Jesus Christ (who came into the world of matter and took on flesh) must also be a created intermediary, not eternal (uncreated) God. This view was championed by Arius, an influential elder (presbyter) in the Christian community located in Alexandria, Egypt. His bishop, Alexander, vehemently disagreed with Arius' view, and tried to remove Arius from his office. But the people protested and the Arian controversy resulted.

The Council of Nicaea
Ruins of the church where the Council met.
In A.D. 325, in order to try to settle the Arian controversy, Roman Emperor Constantine convened a church council in the town of Nicaea in Asia Minor near Constantinople. About 300 bishops attended, most from the East. They debated the nature of God and of Jesus Christ, most rejecting Arius' idea that Jesus was a created being. They believed that in worshiping Jesus, they were worshiping God. They believed they were saved by God, not by a created being. In short, they were convinced that Scripture declares that Jesus Christ is God.

Of one substance (homoousios)
To affirm this belief, the council wrote the Nicene Creed, which declares that Jesus Christ is, "God of God, light of light, true God of true God, begotten, not made, of one substance with the Father." The last portion had particular significance in the council. The phrase of one substance translates the Greek word homoousios, which means "of the same substance or essence - of one being." The Nicene Creed thus declares that what God is in his substance (essence, being), the Son of God is as well. We'll have much more to say about this vital truth as we proceed.

The debate continues: The Council of Constantinople 
Following the Nicene Council, the debate continued, including discussions about the Holy Spirit. The Nicene Council had merely said that "we believe in the Holy Spirit," without saying anything about who or what the Spirit is. Contrary to Arius' teaching that the Holy Spirit was a created spirit being, others, such as Athanasius of Alexandria, believed and taught that the Holy Spirit, like Jesus Christ, is divine.
Second Ecumenical Council of Constantinople by Surikov
(public domain via Wikiart)

Eventually, Theodosius (the new Roman emperor), called a second council, which was held in Constantinople in 381. That council affirmed the view of the earlier Nicene Council that Jesus is fully divine, eternal, not created. Moreover, the council accepted the full divinity of the Holy Spirit, teaching that the Father is God, the Son is God, and the Holy Spirit is God, yet there is only one God - one God in three Persons. They felt compelled by Scripture to come to this conclusion.

The Nicene Creed
The result of these two councils (with some later editing) is known as the Nicene-Constantinopolitan Creed, often referred to as the Nicene Creed. Here is the text of the Creed (as translated by the International Consultation on English Texts, 1975):
We believe in one God the Father, the Almighty, creator of heaven and earth, and of all that is, seen and unseen.
We believe in one Lord, Jesus Christ, the only Son of God, eternally begotten of the Father, God from God, Light from Light, true God from true God, begotten, not made, of one being with the Father. Through him all things were made. For us men and for our salvation he came down from heaven; by the power of the Holy Spirit he became incarnate from the Virgin Mary, and was made man. For our sake he was crucified under Pontius Pilate; he suffered death and was buried. On the third day he rose again in accordance with the Scriptures; he ascended into heaven and is seated at the right hand of the Father. He will come again in glory to judge the living and the dead, and his kingdom will have no end. 
We believe in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father (and the Son). With the Father and the Son he is worshiped and glorified. He has spoken through the Prophets. 
We believe in one, holy, catholic and apostolic Church. We acknowledge one baptism for the forgiveness of sins. We look for the resurrection of the dead, and the life of the world to come. 
As we progress through this article, we'll unpack the Creed, noting its essential points in defense of the incarnational Trinitarian faith (what TFT refers to as the "Nicene Faith") which is grounded in the Gospel given by Jesus, taught by his Apostles, and recorded in Holy Scripture. There is much to learn, and as we do, we'll find cause to rejoice.

The Creed begins with a short, yet important and profound phrase:

We believe...

The Creed defines the content of this belief in a way that has stood the test of time, being embraced by Christians of nearly every denominational stripe for over 1600 years! According to Athanasius, who was an influential delegate at Nicaea, the Creed sets forth "the divine and apostolic faith" (p15). According to TFT, it presents the "simple first principles of the Gospel" (p16).

The chief concern of Athanasius, and the other  framers of the Creed, was to clarify and defend what the Apostles taught concerning the nature of our triune God. The resultant, carefully chosen words constitute the heart of our Christian faith, which is the doctrine of the Trinity. This doctrine is not merely of academic importance. It speaks to all aspects of the church's being and doing including its worship and mission.

In defining this doctrine and others that flow from it, the Creed places a protective 'boundary' around the Christian faith. Thus, it is of immense significance to the church, and on that basis should be taught (in my view) to all Christians, and repeated as a confession of faith in Christian worship.

However, a word of caution is in order here: The Creed is not the truth! Rather, the truth is God himself. And that truth comes to us principally not in words, but in God's self-revelation in the person and work of Jesus Christ (p.23). And so we worship the triune God, not words about him, though words about him are very helpful (even essential) to our worship.

In reading the Creed, we also are mindful of the limitations of human language. Even with prayerful, biblically informed consideration, the councils that framed the Creed were "forced to stretch the feeble capacity of...language to give expression to indescribable realities" (p27). That being said, the words of the Creed have stood up remarkably well over 1600 years of study, debate, and worship. It uses words of great meaning that we would do well to seek to understand. Indeed, this humble article is given to that purpose.

Some Christians object to the Creed, because it uses words not found in Scripture. I appreciate this concern; it was one I once held. But I came to realize that the Holy Spirit, through Holy Scripture, leads us to seek a deep understanding of God, and then to convey that understanding to others, using words not found in Scripture if need be. Sometimes we may even need to coin a new word, such as "trinity".

Athanasius, who was a careful and faithful student of Scripture, pointed out that it does not matter whether a person uses a non-scriptural word or not, so long as he has a "godly mind." As TFT notes, this father of Nicaea, far from speaking irreverently of Christ, spoke of him with "an exalted mind and a Christ-loving godliness" (p42). May we do so as well!

Let's now look at the larger first phrase of the Creed:

We believe in one God... 

The Creed proclaims belief in "one God" and then goes on to describe this one God as existing in three persons. This approach was carefully conceived in order to combat heresies infecting the fourth century church. Of particular concern was the dualistic idea that God (being spirit and thus transcendent), is necessarily separate from the material world, including humanity. This non-biblical worldview, which emerged out of pagan Greek philosophy, was embraced by some influential church leaders. As a result, some denied Jesus' humanity, while others (notably Arius of Alexandria) denied Jesus' divinity. Arius and others also denied that the Holy Spirit was a divine person. The Council went on the offensive against these heresies, seeking to understand and uphold what Scripture declares to be true of the triune God revealed in and through the incarnate Son of God, Jesus Christ, who...

...Came among us as man; and by what he was as man...revealed to us what he was and is as God. That is to say, without giving up his divine nature, he united himself to us in our human nature so completely, that by living out his divine life within our human life as a real human life he revealed something of the innermost secret of his own divine life as Son of the Father (p55).
In Jesus, all dualistic views of God and of the world (including humanity) are obliterated. In his divinity, Jesus shares with the Father and the Holy Spirit the one being of God. Thus our knowledge of the Father and of the Holy Spirit coincide in the person of Jesus, who as TFT notes, is "the very reality of God in his self-communication to us" (p63). Jesus said it very simply: "If you have seen me, you have seen the Father" (John 14:9). Jesus reveals God because Jesus is God.

The Nicaean Council wrestled to understand, accurately communicate, and thus defend this trinitarian revelation. Its profound assertions state that the Father, Son and Holy Spirit, though not the same person, share the one being of the one God. Said another way, God who is one in being, is three in person.

Though we barely have begun the Creed, already we are confessing that there is "one God," and that this one God is tri-personal. Thus, the Creed immediately asserts the identity of the first person of the Trinity, "the Father." TFT comments:

"...The very center of saving faith is belief not merely in God, but in God as Father; not merely in Christ but in Christ as the Son of God... It is understanding of the Fatherhood of God, mediated in and through the Person and Work of Jesus Christ, his beloved Son, that governs all that is truly thought and said of God (p77).
And that includes what is thought and said of God in his work, including his work of creation. This is the issue that the Creed next addresses as it addresses belief in God the Father:

[We believe in one God] the Father Almighty, Maker of heaven and earth and of all things visible and invisible.

Here the Creed is asserting that the one God, in the person of the Father Almighty, is Creator (Maker) of all that is.

As noted earlier, the Creed emphasizes that God is one in being (Gk=ousia). Yet now the Creed begins to speak of the three persons of the one God, beginning with the Father, who as Almighty, is associated with his act of creating. This does not mean that the Father is Creator to the exclusion of the Son and the Holy Spirit. Rather (as noted by TFT), the Creed is granting "primacy to the concept of the Fatherhood of God, for knowledge of God as Creator is taken from knowledge of God as Father, and not the other way round" (p76). And, of course, we receive this knowledge of the Father through the Son, by the Spirit.

The point being made is that the Father Almighty is the Source (or Fount) of all being - both the being of God (which is ultimate being), and the being of the creation, which is granted its being by God, who creates all that is out of nothing. Thus the creation is from the Father (as creative Source), through the Son (as creative Word), in the Holy Spirit (as creative Agent).

In associating the Fatherhood of God with the act of creating, the Creed is not asserting that God became Father by creating. The Father has always been Father (and thus it follows that the Son has always been Son of the Father). However, there was a time when the Father was not Creator. As TFT notes, "God always had the power to create [he is the Father, Almighty], and did actually create because he was and is the Father of the Son. God is, and always is, Father, but to create something out of nothing utterly different from himself is an act of his will and freely follows from what he eternally and intrinsically is" (p87a).

Following Athanasius, TFT draws a parallel between this original act of creation and God's subsequent act of incarnation. In both, God acts to create something entirely new (p88). There was a time when there was no creation, but God, as Father, became Creator and created the cosmos out of nothing. Similarly, there was a time when the eternal Son of God was not human, but became human through the incarnation, which is a stunning act of re-creation.

The reason for both creation and re-creation (incarnation) is that God does not will to exist for himself alone. God, who is complete in himself (three-in-one; one-in-three), lacks nothing and thus has no need for a creation. Rather, because God in his own triune nature is love, he wills to create in order to love his creation:

He does not will to exist for himself alone, but has freely and spontaneously brought a world into existence out of non-existence... Although he is utterly transcendent he does not hold himself aloof from his creation, but is freely present and at work within it, intervening personally and providentially in the events of the world and in the affairs of his human creatures... God created all things out of nothing and wishes them to exist as objects of his loving-kindness which he has now manifested to the world in Jesus Christ" (pp90-91).
Thus, according to TFT, "the whole raison d'etre of the universe lies in the fact that God will not be alone, that he will not be without us" (p94). We were created for communion with the triune God of love, and in Christ we were re-created to make that communion possible, despite our sin. And so the Creed leads us to worship God the Father, who in his Almighty love both creates and re-creates, providing for all humanity (the object of his love) a means to share forever in his divine, triune communion.

Next, the Creed addresses the Son of God, Jesus Christ:

[We believe in] Lord Jesus Christ, the only begotten Son of God, begotten from his Father before all ages, Light from Light, true God from true God, begotten not made, of one being with the Father, through whom all things were made.

Note how this clause defines Christ as from his Father. In this eternal relationship, he is begotten not made. The Father-Son relationship precedes any Creator-creature relationship. This, of course, was a key issue when the creed was written. All sorts of heretical ideas conceived of Jesus as some sort of creation of God rather than as true God. The creed shows such ideas to be false by asserting the biblical truth that Christ is the One through whom all things were made. Thus when we are confronted in the Gospels with Jesus Christ as a man, we understand that he is God become man, while remaining God. And thus we are taken to the doctrine of the incarnation. Note TFT's comment:
The New Testament did not present Jesus Christ in contrast to God or alongside God, or argue from one to the other, as in ebionite or docetic Christologies [heretical doctrines that denied either the full divinity or the full humanity of Jesus Christ], but presented him in the undivided wholeness of his divine-human reality as God become man (p114).
TFT's thought derives from Athanasius' stress on Christ as 'whole man and God together' (footnote 6, p114). If Jesus Christ were not fully God, we would not have in him the full revelation of God. But Jesus insisted that to see him is, indeed, to "see the Father" (John 14:9). TFT continues:
That Jesus Christ is God's Son or Word, and that God's Son or Word is Jesus Christ, was the central evangelical truth which the Council of Nicaea reaffirmed, and had to reaffirm, in order to cope with... [various false] Christologies, threatening the integrity of the Church's faith. The church refused to weaken or compromise faith in Jesus Christ as God and man in one Person, for if he was not really God then there was no divine reality in anything he said or did, and if he was not really man then what God did in him had no saving relevance for human beings (p115).
One being with the Father
This part of the creed spells out in detail how it is Christ is related to the Father. It does so with an essential phrase that declares Christ to be of one being with the Father (homoousius to Patri in Greek). To this phrase is added, through whom all things were made, so as to emphasize the identification of the Son with the Creator (and thus that the Son preexists creation).

The point is that Jesus Christ as fully God, shares with the Father the one being (ousius in Greek, meaning being, substance or nature) of God. Jesus Christ is fully God in his very being and nature. To make this clear, the creed applies the biblical expressions of by, from and of God to the incarnate Son. What is the very being of the Father is entirely the being of the Son. Said another way, Jesus Christ is the Son of the Father from his very being, that is, from his essential reality and nature. TFT elaborates:

The Father/Son relation falls within the one being of God, the Father and the Son inhering and coexisting eternally, wholly and perfectly in one another. God is Father precisely as he is eternally the Father of the Son, and the Son is God of God precisely as he is eternally Son of the Father. There is perfect and eternal mutuality between the Father and the Son, without any 'interval' in being, time or knowledge between them (p119).
This is in keeping with the teaching of Athanasius that "the son is continuously co-eternal with the Father" (footnote 28, p120). This idea is expressed in the creed using the biblical image of light:
[Just as] light is never without its radiance, so the Father is never without his Son or without his Word. Moreover, just as light and radiance are one and are not alien to one another, so the Father and the Son are one and are not alien to one another but are of one and the same being. And just as God is eternal light, so the Son of God as eternal radiance of God is himself eternally light without beginning and without end (p121).
Athanasius emphasized the essential oneness (the homoousion in Greek) of the Father and the Son by stating that "the Son is everything that the Father is, except Father" (p124). TFT puts it this way: "The incarnate Son has all the prerogatives of God, except Fatherhood" (p124).

So what?
TFT goes on the discuss at length the great significance of the homoousial relationship between the Father and his Son. An important point is that it is this concept that served as the measuring rod (canon) by which many of the individuals who authored the creed, also determined which books were to be accepted into the New Testament canon. Only those books that upheld the essential oneness of the Father and the Son were accepted. Other books (and there were many that were evaluated) were rejected. In short, the homoousian served as the hermeneutical principle by which the content of the New Testament was established for the church. If follows that the same principle should serve as the hermeneutical principle by which the meaning of these books is ascertained today.

This principle, of course, points to the ultimate canon of Scripture and, indeed of all truth - a who, not a what: the Lord Jesus Christ. Here are some of TFT's comments on this vital point:

The primary and all-embracing significance of the homoousion was its categorical assertion that Jesus Christ is God, and that as God he shares equally with the Father in the one being of the Godhead. As the only begotten Son of the Father he is the embodiment of the whole being of God and his exclusive self-revelation as the Word made flesh (p133). 
To believe in the Lord Jesus Christ is to believe in God himself... In the incarnation God has revealed himself to us... God is completely identical with his self-revelation in Jesus Christ. ...The Son of God in his incarnate Person is the place where we may know the Father as he is in himself... The homoousion asserts that God is eternally in himself what he is in Jesus Christ, and, therefore, that there is no dark unknown God behind the back of Jesus Christ, but only he who is made known to us in Jesus Christ (p135)....The utterly astonishing thing proclaimed in the Gospel is that God himself came among us precisely as man... in body, mind and soul (p136).
This is good news, because it means that there is "no division between the acts of the Son and the acts of God" (p137). In Jesus we see (and taste and feel!) that God truly is for us. TFT comments:
God himself is the content of his saving grace in Jesus Christ. In Jesus Christ the Giver of grace and the Gift of grace are one and the same, for in him and through him it is none other than God himself who is savingly and creatively at work for us and our salvation (p138). 
Nicene theology rejected entirely  the idea that grace is a created medium between God and man. Rather is grace to be regarded as the self-giving of God to us in his incarnate Son in whom the Gift and the Giver are indivisibly one (p14).
And now, with this concept in mind, let us fast forward to the final judgment. There we find that our Judge is none other than this incarnate Son, Jesus Christ. It is he who will judge all humans at the Last Day. Or as Michael Card sings, we will "look into our Judge's eyes and see our Savior there." The God who judges is no different than the God who saves. And that is VERY good news - based not on hopeful speculation, but on the eternal homoousial relation between the Father and his incarnate Son, our Savior, Jesus Christ.

The Creed continues to address the Son of God, now defining the Person and work of Jesus:

[We believe Lord Jesus Christ]...who for us men and our salvation, came down from heaven, and was made flesh from the Holy Spirit and the Virgin Mary, and was made man and was crucified for us under Pontius Pilate. He suffered and was buried, and the third day he rose again according to the Scriptures and ascended into heaven, and sits on the right hand of God the Father. And he shall come again in glory to judge both the living and the dead; his kingdom shall have no end.

A key point here is that our salvation is the act of God himself, who through the Incarnation...
...takes the concrete form of the actual historical man Jesus. As St Paul had expressed it: "God our Savior desires all men to be saved and to come to the  knowledge of the truth. For there is one God, and there is on Mediator between God and men, the man Christ Jesus who gave himself a ransom for all" [1Tim 2.4-6]. For Athanasius [a primary author of the Creed] this meant that the mediation of Christ involved a twofold movement, from God to man and from man to God, and that both divine and human activity in Christ must be regarded as issuing from one Person. Here we see again the soteriological [saving] significance of the Nicene homoousion: If Jesus Christ the incarnate Son is not true God from true God, then we are not saved, for it is only God who can save; but if Jesus Christ is not truly man, then salvation does not touch our human existence and condition. The message of the Gospel, however, is that Jesus Christ embodies in his human actuality the personal presence and activity of God. In him God has really become man, become what we are, and so lives and acts, God though he is, "as man for us." Only God can save, but he saves precisely as man - Jesus Christ is God's act... (pp148-9).
Thus the doctrine of the Incarnation stands at the center of the Creed's assertion that salvation is fundamentally personal. It is accomplished by who the Son of God is and by what he does in person by becoming fully and truly human (the Incarnation); and as human, being born, living, suffering, dying, rising and ascending on our behalf. This points to the related doctrine of the vicarious (representative-substitutionary) humanity of Jesus:
It was the whole man that the Son of God came to redeem by becoming man himself and effecting our salvation in and through the very humanity he appropriated from us - if the humanity of Christ were in any way deficient, all that he is said to have done in offering himself in sacrifice "for our sakes", "on our behalf" and "in our place" would be quite meaningless....The whole life of Christ is understood as a continuous vicarious sacrifice and oblation which, as such, is indivisible, for everything he assumed from us is organically united in his one Person and work as Savior and Mediator" (p152).
TFT emphasizes that the human nature, which the Son of God assumed in the Incarnation, was the same nature we have, "the defiled nature of man" (p153). This is vital to understand, because it is only by being united with the person of God that our defiled human nature is healed. Thus we understand that the atoning work of Jesus on our behalf is something that happens within Jesus' own Person...
...within the incarnate constitution of his Person as Mediator... As the Head of creation, in whom all things consist, he is the only one who really can act on behalf of all and save them. ...Thus the redemptive work of Christ was fully representative and truly universal in its range. Its vicarious efficacy has its force through the union of his divine Person as Creator and Lord with us in our creaturely being, whereby he lays hold of us in himself and acts for us from out of the inner depths of his coexistence with us and our existence in him, delivering us from the sentence of death upon us, and from the corruption and perdition that have overtaken us (pp155-6). 
TFT continues:

Through his incarnation the Son of God has made himself one with us as we are, and indeed made himself what we are, thereby not only making our nature his own but taking on himself our lost condition subject to condemnation and death, all in order that he might substitute himself in our place, discharge our debt, and offer himself in atoning sacrifice to God on our behalf. Since sin and its judgment have affected the actual nature of death as we experience it, Christ has made our death and fate his own, thereby taking on himself the penalty due to all in death, destroying the power of sin and its stronghold in death, and thus redeeming or rescuing us from its dominion (p157).
Thus the Creed emphasizes that the Incarnation was essentially redemptive and conversely, that redemption is inherently incarnational. Said another way, Jesus in his own Person is the atonement. Our reconciliation with God is not merely something Jesus did (external to himself), but something that he is in himself. This is why forensic (legal) theories of the Atonement are flawed. These theories conceptualize salvation as a transaction, rather than as the personal/relational act it truly is. If you take away the Incarnation, you remove the very ground of salvation. "God in Christ has substituted himself for us in making our sin and death his own that we may partake of his divine life and righteousness" (p161). God accomplished this atoning exchange for us, by transferring, in Christ... himself [our] fallen Adamic humanity which he took from the Virgin Mary, that is, our perverted, corrupt, degenerate, diseased human nature enslaved to sin and subject to death under the condemnation of God. However, far from sinning himself or being contaminated by what he appropriated from us, Christ triumphed over the forces of evil entrenched in our human existence, bringing his own holiness, his own perfect obedience, to bear upon it in such a way as to condemn sin in the flesh and to deliver us from its power (p161)

 The whole incarnational assumption of our human nature was at the same time a reconciling, healing, sanctifying and recreating activity. In making himself one with us he both took what is ours and imparted to us what is his (p162).
This atoning, redeeming exchange between us and Christ is at the heart of the Creed's doctrine of salvation - he became what we are in order that we might share in what he is - thus restoring our communion (fellowship) with God. Truly, our salvation is in Christ - the one who forever, and on our behalf, is fully divine and fully human.

We come now to the clause in the Creed that addresses God the Holy Spirit:

[We believe] the Holy Spirit, the Lord, the Giver of Life, who proceeds from the Father, who with the Father and the Son together is worshiped and glorified; who spoke by the prophets.

As TFT notes, the Creed presents the Holy Spirit as...
...God himself ...immediately present in our midst, miraculously and savingly at work, and through him God reveals himself as Lord, for God himself is the content of what he does for us and communicates to us. The Spirit is not just something divine or something akin to God emanating from him, not some sort of action at a distance or some kind of gift detachable from himself, for in the Holy Spirit God acts directly upon us himself, and in giving us his Holy Spirit God gives us nothing less than himself" (p191).
TFT continues:
The Spirit of God is not the emission of some divine force detachable from God but the confrontation of human beings and their affairs with his own Self in which he brings the impact of his divine power and holiness to bear directly and personally upon their lives in judgment and salvation alike (pp192-3).
The deity of the Spirit and the doctrine of the Trinity
The Creed thus presents the biblical teaching that the Holy Spirit, with the Father and the Son, is fully God and thus is both the subject and object of our worship. As TFT notes,

Faith in the Holy Spirit is to be held in a trinitarian frame in accordance with the ordinance of holy baptism into the one name of Father, Son and Holy Spirit...(p193).
Indeed, the trinitarian baptismal formula in Matthew 28:19 was of particular importance to the framers of the Creed in upholding the deity of the Holy Spirit, and establishing the doctrine of the Trinity. The framers also looked to several other passages of Scripture, including:

  • Mat 3:13-17, which tells of Jesus' baptism, where the Father acknowledges Jesus as his beloved Son and the Holy Spirit descends upon Jesus, anointing him as the Christ. 
  • 2 Cor. 13:14, which tells of the Son's grace, the Father's love, and of the communion of the Holy Spirit. 
  • 1 Cor 12:4-6, which tells of diversities of gifts but of the same Spirit, Lord (Son) and God (Father).
  • Acts 2:32-33, 1 Pet 1:2, 2 Thess 2:13-14, Eph 2:18 and Eph 4:4-6, which all include the triadic formula in one form or another.
TFT comments:
...A definite doctrine of the Trinity was found to arise out of a faithful exegetical interpretation of the New Testament and out of the evangelical experience and liturgical life of the Church from the very beginning. It made explicit what was already implicit in the fundamental deposit of faith. It was with the formulation of the homoousion [meaning "of one being"] clarifying and expressing the essential connection of the Son to the Father upon which the very Gospel rested, and with the application of the homoousion to the Holy Spirit to express his oneness in being with the Godhead of the Father, that the theological structure the trinitarian understanding of the Godhead unfolded and established itself firmly within the mind of the Church (p199).
Thus the Creed teaches that to be indwelt by the Holy Spirit is to be indwelt by God himself. Indeed, the Holy Spirit is "the Lord God in the full reality of his divine life and being... In sending to us his Spirit God has given us, not just something of himself, but his very Self" (p209).

The Spirit's gifts to humanity
When the Holy Spirit comes, he does so from the inner communion of the Holy Trinity. And as he comes, he brings God's own revelation, life-giving power and manifold gifts. This revelation is not of the Spirit himself, but through the Spirit of the "Face of the Father...seen in the Son" (p212). Thus we understand that our understanding of God is "from the Father, shining in the Son and becoming manifest through the Spirit" (p212). Viewed from our perspective, this means that "our mind, enlightened by the Spirit, looks toward the Son, and in him as in an image, sees the Father" (p212). Hallelujah!

Along with this revelation of God, the Holy Spirit brings to us God's own life-giving power and his many spiritual gifts (p220, 225). These are not merely things that God has, but what God, in himself, is. As TFT is fond of saying, "The Giver and the Gift are one." He continues the thought...

We must think of the Holy Spirit, then, as the creative, energizing, enlightening presence of God who freely interacts with his human creatures in such a way as to sustain their relation to himself as the source of their spiritual, personal and rational life (p227).... Moreover by his presence the Holy Spirit is the 'place'... where men may meet with God and are enabled to have communion with him, receive his revelation and worship him (p229). 

We come now to the clause in the Creed that addresses the Church:

[We believe] the one, holy, catholic and apostolic Church.

The Adoration of the Trinity
by Albrecht Durer, 1511
Note first that this clause flows from the one preceding concerning the Holy Spirit. The church exists because of the Spirit's work, not independently from the Spirit. We believe in the church because we believe in the Spirit.

Note next that the Creed declares the church to have four identifying characteristics: one, holy, catholic and apostolic. These four are sometimes referred to as the "marks" of the Church. It is vital to see these marks within the overall incarnational Trinitarian context of the Creed.

1. The Church is one
The Creed declares that the church to be one in the sense that it is rooted in and thus expresses the essential oneness of the triune God. Reflecting on this, TFT writes this:

[The Church is] the empirical community of men, women and children called into being through the proclamation of the Gospel, indwelt by the Holy Spirit in whom it is united to Christ and through him joined to God. Far from being a human institution it was founded by the Lord himself and rooted in the Holy Trinity. As Ignatius of Antioch [an early Church leader who may have been a disciple of John] taught that the members of the Church are united with Jesus Christ just as he is united with the Father. Hence whatever the Church does from beginning to end is done 'in the Son and the Father and the Spirit'. The Church is what it everywhere is in the world as a manifestation of the saving union with God incarnate in Jesus Christ....'Wherever Jesus Christ is, there is the universal Church' (p253).
Making reference to the writings of Irenaeus (which preceded, but heavily influenced, the writing of the Creed), TFT continues:
The [Church] is what it is through the incarnation of the Son of God in Christ who has gathered up and reformed the human race in himself, and through the astonishing event at Pentecost when God poured out his own Spirit upon the apostles and disciples of the Lord Jesus thereby giving birth or rather rebirth to the Church and making it participate in his own divine life and love (p254).
This Christocentric understanding of the church tells us that that the Church is formed to be a servant of Christ who, in the power of the Holy Spirit, is a servant of the Father's mission and kingdom. Thus "the Lord Jesus Christ and the Holy Spirit occupied the unqualified center of Christian faith and life empirically as well as spiritually" (p255).

One through one baptism
It's vital to note that the creed grounds the Church's oneness in the "one baptism" in the one name of the triune God: Father, Son and Holy Spirit. This baptism is seen as the means by which people enter the one Church. As TFT notes, the early church prepared candidates for baptism with thorough instruction in the Gospel. Thus baptism is grounded in the Holy Trinity and related directly to the truth of the Gospel. In this context, TFT expands his definition of the Church:

Thus the Church may be described as the place in space and time where knowledge of the Father, the Son and the Holy Spirit becomes grounded in humanity, and union and communion with the Holy Trinity become embodied within the human race. Expressed the other way round, the Church is constituted by the Holy Spirit as the empirical counterpart of his sanctifying presence and activity in our midst, for in the Spirit we are made members of Christ the incarnate Son and through him have access to the Father... As Irenaeus...expressed it: "This Gift of God has been entrusted to the Church, as breath was to the first created man, that all members receiving it may be vivified, and the communication of Christ has been distributed within it, that is, the Holy Spirit, the earnest of incorruption and the confirmation of our faith, as the ladder of ascent to God... For where the Church is there is the Spirit of God; and where the Spirit of God is, there is the Church, and every kind of grace; but the Spirit is truth." As such the Church is constituted by Christ to be the receptacle of the Gospel proclaimed and handed on by the apostles... It was ultimately in the Gospels themselves that Irenaeus located the vivifying deposit committed to the Church, and handed on by the apostles. In this conception of the Church Irenaeus was clearly drawing out the implications of the New Testament injunction about "the faith once for all delivered to the saints" (p257). 
In this way we are given to think of the Church as indwelt by Christ himself, who comes "clothed with the Gospel" (see p258). In this we see the importance of the Church's calling to proclaim the Gospel as it is presented in the writings of the Apostles (the New Testament). Through this proclamation, Jesus himself is proclaimed and through that proclamation the saving Word and power of God is at work in people's lives (see p260). In that context, TFT adds this to his definition of the Church:

The Church [is] the community called to believe in Jesus Christ as Lord and Savior, and brought into union and communion with God the Father through baptism and the regenerating gift of the Holy Spirit. By its very nature, therefore, the Church is tied up with the tradition of the apostolic...Gospel which is handed on from generation to generation with baptism: instruction in the faith which was once for all delivered to the saints and baptism in the name of the Father, Son and Holy Spirit are thus inseparable (p261).

One through union and communion with the triune God
It's also vital to note that the creed grounds the Church's oneness in its union and communion with the Holy Trinity. As noted by TFT, the Trinity is...

The regulative center to which all the worship, faith and mission of the Church take their shape: from the Father, through the Son and in the Spirit, and to the Father, through the Son and in the Spirit (p263a). 
The Creed thus proclaims a Christ-centered, incarnational (participatory) Trinitarian ecclesiology (doctrine of the Church). TFT continues:
Everything we say of the Church must be consistent with the consubstantial oneness between the Son and the Father and be an expression of the union and communion between God and man effected in the incarnate life and reconciling work of the Mediator [Jesus Christ]. That is to say, the doctrine of the Church must be expounded in terms of its internal relation and not some external relation, to Jesus Christ, for it is in Christ and his inherent relation to the Father and the Holy Spirit that the essential nature of the Church is to be found (p264).
This vital truth is the heart of Athanasius' biblical doctrine of the Church as the one Body of Christ. Note TFT's commentary here:
It is not due to some external relation in moral resemblance to Christ that the Church is his Body, but due to a real participation in him who is consubstantial with God the Father (p265a).
This participation (koinonia, communion) with Christ, which makes us his one Body, "is not one of nature but one of adoption and grace effected through the gift of the Spirit who comes to dwell in us as he dwells in God" (p265b). Thus this union and communion is deeply personal in that it happens within the incarnate person of Jesus himself, who in his dual nature as God and man, has united God and humanity in one person (p266).

Moreover, Jesus...

...Makes our humanity in him partake of the Holy Spirit with which he has been anointed and sanctified as man for our sakes, and thereby unites it through himself with the Godhead... The Church is thus to be regarded as constituting all who are reconciled to God in one body through the Cross and are made one in Christ, united with his humanity in such a way that he now comprises both in himself, their humanity and his own, as 'one new man,' for he is in them as they are in him (p267).
TFT then emphasizes that the Church is the one Church of Christ only as it...
...Looks away from itself to its objective source and ground in the Godhead, and dwells in the Holy Trinity, for it is in the Father, Son and Holy Spirit that the Church and its faith are rooted and founded.... The Church is truly Church in so far as it dwells in the Holy Trinity and embodies the truth of the Gospel in its empirical life and worship (p268).
The Church's dwelling in the Holy Trinity is in Jesus, who in his representative humanity is the Church (p270). As members of this Church we are given to participate in the one Body of Christ. This participation is actualized through the one faith and one baptism of the Church (see pp269, 278). With this understanding our definition of what constitutes the one Church is being focused. Though all humanity has, via the incarnation, life, death, resurrection and ascension of Jesus, been (objectively) united to Christ, it is not accurate to say that all humanity is the Church. Rather, Jesus himself is the Church and we humans are part of his one Body as we, through the power of the Holy Spirit, personally (subjectively) participate.

Though the Spirit is at work in all people (poured out on "all flesh"), he is sent from the Father and the Son with a particular ministry of sanctification in the lives of those who are participants in the Church.

As TFT notes...

The Church constitutes the sanctified community within which we may draw near to the Father through the Son and in the Spirit and share in the eternal life, light and love of God himself (p275). 
Thus through the communion [koinonia, participation] of the Holy Spirit imparted to it by Christ, the Church is united to Christ as his body (p277). 
Through the pouring out of the Holy Spirit upon it, the Church [is] constituted the unique 'place' where access to the Father through the Son [is] grounded in space and time among the nations of mankind (p278).
2. The Church is holy
As noted by TFT on p252, the Creed shows that the Church is holy because it is formed by the Holy Spirit (note in that regard, that the Creed's section on the Church follows immediately its section on the Holy Spirit - this is no accident). We are to revere and honor the Church as holy because upon it is the imprint of the character of the Holy Trinity. The Church's holiness is not its own, but rather its sharing in the holiness of God himself (see more about the Church's holiness below).

Though, as noted by TFT, holiness is God's will for the Church...

...[it] does not derive from any moral goodness or purity of its members, but from the holiness of God the Father, the Son and the Holy Spirit. The holiness of the Church is thus objectively grounded in the utterly transcendent holiness, glory and purity of God's being (pp280-281).
God comes among his people, the Church, and in doing so sanctifies them - or as TFT says, "implicates them" in God's own holiness. Coming among them as a holy God would annihilate his people, except that he comes with grace and mercy, and, ultimately, he comes through the incarnation of his Son. In Jesus Christ, God takes our diseased humanity into himself where it is sanctified (made holy). TFT comments:

Since the Church was brought into being through [the Son of God's] assumption of our fallen and enslaved humanity into himself, the self-sanctification of Christ as the Holy One in its midst brings the holiness of the Holy Spirit to bear upon it in conviction and judgment of its unrighteousness, but nevertheless in such a way that the Church is justified in Christ and made holy with his holiness (pp281-282).
Thus the holiness of the church (its righteousness and sanctification) is not its own, but is derived from Christ, "who is Righteousness in his own being" (p282).

Jesus then presents his sanctified humanity to the world through his body, the church:

Through the self-sanctification of Christ in its midst and the pouring out of the Holy Spirit upon it, the Church has been chosen by God and set apart as a spiritual house and a royal priesthood to offer spiritual sacrifices acceptable to God through Jesus Christ...[it is thus] the unique place where God is immediately present to us through the Holy Spirit in his very own being as God (p282).
3. The Church is catholic
In saying that the Church is "catholic" the Creed is saying that it is "universal" or "all-inclusive":

The Catholic Church is to be understood as embracing all dimensions of the people of God and their existence throughout space and time, for by the very nature of its unique foundation of Christ upon his apostles, and in virtue of the faith once and for all delivered to it by the apostles, the Church must ever be one and the same in all ages and places (p283).
The Creed thus correlates the catholicity of the Church with its apostolic faith, which is the basis for the church's one doctrine. The church's catholicity is also correlated with the "universal range of the incarnation and atonement" - for the Son of God "died and rose again for all people irrespective of who they are" (p284). TFT comments further:

The oneness of the Church arises out of the interlocking of the incarnation and the atonement... the indivisibility of the Person and work of Christ as the one Mediator between God and man. This one Church is intrinsically catholic because it is the one Body of Christ in whom the fullness of the Godhead dwells bodily in whom all things visible and invisible are gathered up and reconciled to God, and because as the Body of such a Christ the Church is itself the fullness of him who fills all things.

The catholicity of the Church, then, refers to the intensive wholeness and fullness of the Church in Christ, to the coordination of the Church, everywhere, in every place, and throughout all space and time, with the wholeness and fullness of Christ himself (p285). 
4. The Church is apostolic
TFT defines the Church's apostolicity as follows:

In its simplest sense the apostolicity of the Church refers back to the original foundation of the Church once for all laid by Christ upon the apostles, but it also refers to the interpenetration of the existence and mission of the Church in its unswerving fidelity to that apostolic foundation (p285).
The Apostles were chosen and sent by Christ as a link between himself and the church. They would be this link by both teaching and embodying the truth of the Gospel (the deposit of faith), which is "the unrepeatable foundation on which the Church was built" (p286). This deposit includes the content of the Gospel found in the Apostles' writings (the New Testament, which points back to, and thus includes and interprets the Old Testament). However, this deposit is more than information on a page, for the Gospel itself points directly to the life-giving reality of Christ himself. This is vital to understand, for as TFT notes:

It is only in Christ and not out of itself, and only through union and communion with Christ in its faith and mission and not through its own piety, that the Church is continuously sustained....That the Church is apostolic as well as one, holy and catholic, signifies, therefore, that it is ever one and the same with the Church once for all founded by Christ in the apostolate... That is to say, apostolicity has to do with the continuing identity of the Church as the authentic Body of Christ in space and time (p287).
To be truly apostolic in both its belief and ministry, the Church must focus continuously and faithfully on the interpretation, exposition and application of Holy Scripture, which contains the apostolic witness to Christ...

...For it is through faithful transmission of the preaching and teaching of the apostles that the Church is itself constantly renewed and reconstituted as Christ's Church (p287).
The bishops and theologians of the Church who assembled at Nicaea grounded their deliberations in careful exposition of Scripture, even though, at times, they had to coin new terms to adequately express and thus faithfully convey the deposit of faith contained in Scripture. This was particularly needful in formulating statements concerning the triunity of God and the Incarnation of the Son of God. According to TFT:

[The bishops and theologians attending the Council] were concerned in wrestling with the Holy Scriptures to express what they were compelled to think and hold within the context of the apostolic tradition under the impact of God's self-revelation through the Word and Spirit of Christ, and on that basis alone, to confess their faith in the Father, the Son and the Holy Spirit. And thereby they sought to provide continuing generations of people in the Church with an evangelical and apostolic framework within which continuing interpretation of Holy Scripture, proclamation of the truth of the Gospel, and instruction in the faith could be carried out (p289).
We are richly blessed to have inherited this "evangelical and apostolic framework," which defines and thus defends the deposit of faith once and for all given to the church by Jesus through his Apostles. By remaining true to this framework, the Church remains connected to Christ himself, who is the one Apostle in the absolute sense. That connection includes faithfully reading, understanding and teaching the deposit of faith given in Holy Scripture, and it includes faithful participation with Christ in his ongoing apostolic mission to the world, through his body, the Church.

We come now to the Creed's final clause:

We acknowledge one baptism for the forgiveness of sins. We look for the resurrection of the dead, and the life of the world to come. Amen.

The Creed's declaration of the church's apostolicity (see above) provides the basis for its concluding statement concerning the church's one baptism and issues pertaining to eschatology (the resurrection and the life to come).

One baptism 

The framers of the Creed apparently took the phrase one baptism from Paul's letter to the church in Ephesus (Ephesians 4:4-5). Paul exhorts that congregation to a unity grounded firmly in the fact that there is but "one body and one Lord, one faith [and], one baptism."

Why do Paul and the Creed highlight baptism but not the Eucharist? According to TFT, it is because of the important "inner connection between baptism and the wholeness of the apostolic and catholic faith." Indeed, "the whole substance of the Gospel of grace...[is] concentrated in one baptism for the remission of sins" (p290). In making this point, TFT references Athanasius' understanding that the "fullness of the mystery" (the gospel) is found in baptism, which "is given in the name of the Father, Son and Holy Spirit" (p290). Like other early church fathers, Athanasius regarded baptism as....

...The great seal... the all-embracing sacrament bound up with one Body, one Spirit, one Lord, one faith, and one God and Father while the Eucharist was regarded as celebrated only within the Church's participation in the great mystery of baptism and as properly included within it (p. 290).
One baptism thus points directly to Jesus as the one Lord of the church. Indeed, it was through Jesus' vicarious life, death and resurrection that the church came into being. According to TFT, "baptism in his name signified incorporation of the baptized into Christ as members of his Body" (p291).

TFT then shows that one baptism also points to the Holy Spirit...

For it is in one Spirit as well as through Christ that the Church has access to the Father. It is through the koinonia [communion/fellowship] of the Holy Spirit that the Church shares in the incarnate mystery of Christ, and through the power and operation within it that the unity of the Church as the Body of Christ is progressively actualized among the people of God. The Church is thus respected as the Temple of God in which he dwells through his Spirit (p291).
For the forgiveness of sins 
Why does the Creed declare one baptism for the forgiveness of sins? Does baptism bring about that forgiveness? TFT answers that "baptism in the name of the Father, Son and Holy Spirit initiates people into the sphere in which all the divine blessings [including forgiveness of sins]...are bestowed and become effective" (p292). In saying this, TFT is not suggesting that we are forgiven (and thus saved) by baptism (or at the time of baptism). Rather he is noting that in the rite of baptism we experience subjectively (personally) all that Jesus accomplished for humanity objectively, including what he accomplished through his baptism in the Jordan. What is true objectively, becomes personally experienced (or actualized) in our baptism. It's one thing to be forgiven, it's another to experience that forgiveness, and thus have it become effective in our personal lives.

But what is personally (subjectively) experienced is grounded in a greater objective reality. It is to this reality that TFT points. In doing so he notes that Athanasius (like other of the Greek church fathers) regarded Jesus' baptism as a vicarious baptism, which was "a decisive point" for all humanity. He explains:

In his baptism in the Jordan, the incarnate Son of God received the Spirit upon the humanity he had taken from us, not for his own sake, but for our sake. That is to say, it was our humanity that was baptized, anointed, sanctified and sealed in him. Thus when he was baptized for us we were baptized in him. Our baptism in the name of the Holy Trinity, therefore, is to be understood as a partaking through the Spirit in the one unrepeatable baptism of Christ which he underwent, not just in the Jordan river, but throughout his life and in his death [and] resurrection on our behalf. That vicarious baptism was the objective truth behind the one baptism of the Creed in which its depth of meaning was grounded....We are [thus] directed through the rite of baptism to its objective ground and reality, [which is] Christ clothed with the saving truth of his vicarious life, death and resurrection (pp292-3). 
TFT continues:

Baptism is the sacrament of that reconciling and atoning exchange in the incarnate Savior. When we understand baptism in that objective depth, we are directed away from ourselves to what took place in Christ in God (p293).
Thus we understand that it is the objective sense of baptism that is addressed in the Creed's declaration of one baptism for the forgiveness of sins. This phrase then points to the Creed's related phrase concerning eschatology:

We look for the resurrection of the dead, and the life of the world to come. Amen.

Note that the Creed links the resurrection with forgiveness of sins. As noted by TFT, this linkage was of particular importance to the Creed's framers, "for it meant that forgiveness was not in word only but enacted in the concrete reality of human physical existence" (p298).

This linkage also served to expose certain heresies that denied that the Word of God really did become flesh, and really did die and then rise from the dead in flesh (bodily), remaining forever fully God and fully human (now a glorified human). TFT explains:

In his incarnate life, death and resurrection the Son of God established a binding relation between his divine reality an humankind; he not only bridged the gap between the creature and the Creator but triumphed completely over the separation between man and God due to human sin and alienation. The resurrection of  Christ demonstrated the fact that all division between man and God has now been removed in atoning reconciliation through the blood of Christ. Moreover, the resurrection of Christ in body demonstrated that the saving work of Christ on our behalf was fulfilled within the concrete reality of our actual human existence, and in such a way as to set it upon an entirely new basis in the regeneration or renewal of human being in the risen Lord. That was the great message of forgiveness proclaimed at once by the apostles on the day of Pentecost and sealed by the gift of the Holy Spirit in baptism.

To be united to the crucified and risen Christ through the baptism of his Spirit , necessarily carries with it sharing with him in the resurrection of the dead and the life of the world to come. 'Our resurrection is stored up in the Cross,' as Athanasius once expressed it. Through his incarnation the Son of God took up into himself our physical existence enslaved to sin, thereby making our corruption , death and judgment his own and offering  himself as a substitute for us, so that through the atoning sacrifice of his own life, he might destroy the power that corruption and death have over us. Through the resurrection of our physical human nature in himself Christ has set us upon an altogether different basis in relation to God in which there is no longer any place for corruption and death. 'Now that the Savior is risen in his body, death is no longer terrible; for all who believe in Christ trample over it as if it were nothing, and choose rather to die than deny their faith in Christ. They know that when they die, they are not lost, but live and become incorruptible through the resurrection. Thus the central focus of Christian belief is upon the incarnate, crucified and risen Savior, for he has burst the bands of death and brought life and immortality to light - that is the forgiveness of sins and resurrection of the dead into which we are once for all baptized by the Holy Spirit. Far from being just a promise for the future, it is an evangelical declaration of what had already taken place in Christ, and in him continues as a permanent triumphant reality throughout the whole course of time to its consummation, when Christ will return with glory to judge the quick and the dead, and unveil the great regeneration which he has accomplished for the whole creation of visible and invisible realities alike (pp298-9).


We have come to the end of this rather lengthy article exploring the Nicene Creed. I hope you've found it helpful. The emphasis throughout has been on our triune God - the one who in being and activity is one in three and three in one. TFT comments:

For there is from the Father one grace which is fulfilled through the Son and in the Holy Spirit; and there is one divine nature and one God "who is over all and through all and in all" [quoting Athanasius who quotes Ephesians 4:6] (p307).
Let's conclude with a prayer that TFT offers at the end of his book (p340):

Almighty and everlasting God, who hast revealed thyself as Father, Son, and Holy Spirit, and dost ever live and reign in the perfect unity of love: Grant that we may always hold firmly and joyfully to this faith, and, living in the praise of thy divine majesty, may finally be one in thee; who art three Persons in one God, world without end.