The Trinity:
Definition of Terms:
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The Doctrinal Development of the Trinity
The doctrine of the Trinity, a cornerstone of Christian theology, posits that God exists as three distinct persons—Father, Son, and Holy Spirit—united in one divine essence. While this complex belief can be demonstrated through Scripture, it’s articulation evolved over centuries through scriptural interpretation, theological debates, and ecclesiastical councils. While the Old Testament does not explicitly articulate the Trinity, several passages have been interpreted by Christian theologians as hinting at a plural yet unified divine nature. Genesis 1:26 states, “Then God said, ‘Let us make man in our image, after our likeness.’” The plural pronouns “us” and “our” suggest a multiplicity within God’s unity, interpreted by later theologians as an allusion to the Trinity. Similarly, Isaiah 6:3 describes the seraphim proclaiming, “Holy, holy, holy is the Lord of hosts,” with the threefold repetition seen as a Trinitarian echo. Another key passage is Isaiah 48:16, where the speaker (often identified as the Messiah) says, “And now the Lord God has sent me, and his Spirit,” implying the presence of three divine entities.
The New Testament provides more explicit grounds for Trinitarian theology. Matthew 28:19 records Jesus’ command to baptize “in the name of the Father and of the Son and of the Holy Spirit,” presenting the three persons as coequal in authority. John 1:1–14 identifies Jesus as the “Word” (Logos) who was “with God” and “was God,” suggesting both distinction and unity. The relationship between the Father and the Son is further elucidated in John 10:30, where Jesus declares, “I and the Father are one.” The Holy Spirit’s divinity is affirmed in Acts 5:3–4, where lying to the Spirit is equated with lying to God. Additionally, 2 Corinthians 13:14 offers a Trinitarian benediction: “The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.” These passages, while not fully articulating the Trinity, provided the scriptural foundation for its doctrinal development.
Early Christian Heresies and the Need for Clarification
The early Church faced numerous theological challenges that necessitated precise articulation of the Trinity. Several heresies emerged, each distorting the relationship between the Father, Son, and Holy Spirit, prompting rigorous defense from Church Fathers.
Modalism (Sabellianism): This heresy, associated with the priest Sabellius (early 3rd century), taught that the Father, Son, and Holy Spirit were merely different modes or manifestations of a single divine person, denying their distinct personhood. This view undermined the relational distinctions within the Godhead.
Arianism: Proposed by another priest, Arius (c. 256–336), Arianism asserted that the Son was a created being, subordinate to the Father, and not eternally divine. Arius’ slogan, “There was a time when the Son was not,” challenged the Son’s coeternality and consubstantiality with the Father.
Pneumatomachianism (Macedonianism): This heresy, attributed to Macedonius, a 4th century bishop of Constantinople, denied the full divinity of the Holy Spirit, treating the Spirit as a subordinate force or creation rather than a coequal person of the Trinity.
Adoptionism: This belief held that Jesus was a human who was “adopted” as God’s Son at his baptism or resurrection, denying his eternal divinity and preexistence.
These heresies threatened the unity of Christian doctrine, prompting the Church Fathers to articulate and defend orthodox Trinitarian theology.
Church Fathers and the Defense of Orthodoxy
Several Church Fathers played pivotal roles in defending and clarifying Trinitarian doctrine against these heresies:
Tertullian (c. 155–240): Tertullian, a North African theologian, was among the first to use the term Trinitas (Trinity) in his work Against Praxeas. He articulated the concept of one God in three persons (una substantia, tres personae), countering Modalism by emphasizing the distinctness of the persons while affirming their unity in substance.
Athanasius of Alexandria (c. 296–373): Athanasius vigorously opposed Arianism, particularly in his work On the Incarnation and Discourses Against the Arians. He argued for the Son’s full divinity and consubstantiality (homoousios) with the Father, emphasizing that salvation depends on the Son being fully divine.
Basil the Great (c. 330–379): A Cappadocian Father, Basil defended the divinity of the Holy Spirit against Pneumatomachians in his treatise On the Holy Spirit. He argued that the Spirit’s role in sanctification and worship demonstrated his coequality with the Father and Son.
Gregory of Nazianzus (c. 329–390): Another Cappadocian, Gregory’s Theological Orations provided a sophisticated defense of the Trinity, articulating the balance between the unity of essence and the distinction of persons. He famously described the Trinity as “one Godhead in three hypostases.”
Augustine of Hippo (354–430): Augustine’s De Trinitate offered a profound psychological analogy for the Trinity, likening the Father, Son, and Holy Spirit to the mind, knowledge, and love in human consciousness. His work solidified Trinitarian orthodoxy in the Latin West.
These theologians laid the intellectual groundwork for the Church’s response to heresy, shaping the doctrine through their writings and participation in ecclesiastical councils.
Ecclesiastical Councils
To address these heresies and standardize Christian doctrine, the early Church convened several ecumenical councils:
Council of Nicaea (325 CE): Convened by Emperor Constantine to address Arianism, this council produced the Nicene Creed, affirming that the Son is homoousios (of the same substance) with the Father, thus rejecting Arius’ claim that the Son was a created being. The council condemned Arianism and established the Son’s full divinity.
Council of Constantinople (381 CE): This council expanded the Nicene Creed to affirm the divinity of the Holy Spirit, countering Pneumatomachianism. The resulting Niceno-Constantinopolitan Creed declared the Spirit as “the Lord and Giver of Life, who proceeds from the Father, who with the Father and the Son is worshiped and glorified.” It solidified the Trinitarian formula.
Council of Ephesus (431 CE): While primarily addressing Nestorianism (which separated Christ’s divine and human natures), this council reinforced the unity of Christ’s person, indirectly supporting Trinitarian theology by affirming the Son’s full divinity.
Council of Chalcedon (451 CE): This council further clarified Christology but also upheld the Trinitarian framework established at Nicaea and Constantinople, ensuring doctrinal consistency.
These councils formalized the orthodox understanding of the Trinity, defining the three persons as coequal, coeternal, and consubstantial, sharing one divine essence.
The Early Church’s Response to Islam and Accusations of Polytheism
With the rise of Islam in the 7th century, Christians faced new theological challenges, particularly accusations of polytheism due to the Trinitarian doctrine. The Qur’an, in Surah 4:171, admonishes Christians not to say “three” but to affirm God’s oneness, interpreting the Trinity as tritheism. Similarly, Surah 5:73 declares that those who say God is “the third of three” are disbelievers.
Early Christian responses to these critiques varied by region and context:
John of Damascus (c. 675–749): Writing from within the Islamic Umayyad Caliphate, John addressed Muslim accusations in his Fount of Knowledge, particularly in the section On Heresies. He clarified that Christians worship one God in three hypostases, not three gods, emphasizing the unity of divine essence. He also engaged with Islamic theology, respectfully critiquing its rejection of Christ’s divinity while defending Trinitarian monotheism.
Theodore Abu Qurrah (c. 750–820): A Melkite bishop, Abu Qurrah wrote apologetic works in Arabic, such as On the Trinity, to explain the doctrine to Muslim audiences. He used philosophical arguments, drawing on Aristotelian concepts of substance and relation, to demonstrate that the Trinity does not compromise divine unity.
Diplomatic and Polemical Exchanges: In regions under Islamic rule, Christian leaders often engaged in dialogues with Muslim scholars, as seen in the reported debates at the court of Caliph al-Ma’mun (9th century). These exchanges aimed to clarify that the Trinity was not polytheistic but a mystery of one God in three persons. Polemical works, such as those by Nicetas of Byzantium, also emerged, though they sometimes adopted a confrontational tone, accusing Islam of misunderstanding Christian doctrine.
The early Church’s response was shaped by its need to maintain theological integrity while navigating life under Islamic governance. Christians emphasized the monotheistic core of Trinitarian belief, often using analogies (e.g., the sun’s light, heat, and essence) to explain the unity and distinction within the Godhead.
Conclusion
The doctrine of the Trinity developed through a dynamic interplay of scriptural exegesis, theological reflection, and ecclesiastical authority. Old and New Testament passages provided the foundation, while heresies like Modalism, Arianism, and Pneumatomachianism necessitated clarification by Church Fathers such as Tertullian, Athanasius, and the Cappadocians. The Councils of Nicaea and Constantinople formalized Trinitarian orthodoxy, establishing the Nicene Creed as a definitive statement. In response to Islamic critiques, early Christian apologists like John of Damascus and Theodore Abu Qurrah defended the Trinity as a monotheistic doctrine, engaging with Muslim theology in a context of coexistence and debate. The Trinitarian doctrine, refined through centuries of controversy, remains a central tenet of Christian faith, reflecting the Church’s commitment to articulating the mystery of God’s nature.
Footnotes
- Modalism (Sabellianism): For a discussion of Sabellius and Modalism, see Kelly, Early Christian Doctrines, 119–123. Tertullian’s refutation is found in Against Praxeas, Chapters 1–3.
- Arianism: Arius’ teachings are documented in his Letter to Eusebius of Nicomedia, preserved in Theodoret, Ecclesiastical History, Book 1, Chapter 5, in Nicene and Post-Nicene Fathers, Second Series, vol. 3.
- Pneumatomachianism: The denial of the Holy Spirit’s divinity is addressed in Basil the Great, On the Holy Spirit, Chapters 10–12. See also Lewis Ayres, Nicaea and Its Legacy: An Approach to Fourth-Century Trinitarian Theology (Oxford: Oxford University Press, 2004), 211–215.
- Adoptionism: For early Adoptionist views, see Kelly, Early Christian Doctrines, 115–119.
- Tertullian’s Trinitarian terminology: Tertullian’s use of Trinitas and substantia is found in Against Praxeas, Chapters 2–4. See also Eric Osborn, Tertullian, First Theologian of the West (Cambridge: Cambridge University Press, 1997), 116–137.
- Athanasius on Arianism: Athanasius’ defense of the Son’s divinity is detailed in Discourses Against the Arians, Discourse 1, Chapter 13. See also Khaled Anatolios, Athanasius: The Coherence of His Thought (London: Routledge, 1998), 99–124.
- Basil the Great on the Holy Spirit: Basil’s arguments are in On the Holy Spirit, Chapters 16–18. See Andrew Radde-Gallwitz, Basil of Caesarea, Gregory of Nyssa, and the Transformation of Divine Simplicity (Oxford: Oxford University Press, 2009), 143–165.
- Gregory of Nazianzus’ Theological Orations: See Oration 29: On the Son and Oration 31: On the Holy Spirit, in On God and Christ, 69–87, 117–137.
- Augustine’s De Trinitate: Augustine’s psychological analogy is developed in De Trinitate, Books 9–11. See also Lewis Ayres, Augustine and the Trinity (Cambridge: Cambridge University Press, 2010), 178–205.
- Council of Nicaea (325 CE): The Nicene Creed and proceedings are documented in Decrees of the Ecumenical Councils, vol. 1, ed. Norman P. Tanner (Washington, DC: Georgetown University Press, 1990), 1–19. See also Ayres, Nicaea and Its Legacy, 85–100.
- Council of Constantinople (381 CE): The Niceno-Constantinopolitan Creed is found in Tanner, Decrees of the Ecumenical Councils, 21–35. For its Trinitarian significance, see Kelly, Early Christian Doctrines, 255–261.
- Council of Ephesus (431 CE): The council’s Christological focus indirectly supported Trinitarian doctrine. See Tanner, Decrees of the Ecumenical Councils, 41–66.
- Council of Chalcedon (451 CE): The Chalcedonian Definition is in Tanner, Decrees of the Ecumenical Councils, 83–87.
- Qur’anic critiques of the Trinity: See The Qur’an, trans. M.A.S. Abdel Haleem (Oxford: Oxford University Press, 2004), Surah 4:171 and Surah 5:73.
- John of Damascus on Islam: John’s discussion of the Trinity and Islam is in Fount of Knowledge, Part 2: On Heresies, Chapter 101, in Writings, trans. Frederic H. Chase Jr. (Washington, DC: Catholic University of America Press, 1958), 153–160.
- Theodore Abu Qurrah’s apologetics: See Theodore Abu Qurrah, trans. John C. Lamoreaux (Provo, UT: Brigham Young University Press, 2005), particularly On the Trinity, 184–204.
- Christian-Muslim dialogues: For accounts of early dialogues, see Sidney H. Griffith, The Church in the Shadow of the Mosque: Christians and Muslims in the World of Islam (Princeton, NJ: Princeton University Press, 2008), 75–94.
Bible Verses:
Matthew 28:19:
“Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.”
2 Corinthians 13:14:
“The grace of the Lord Jesus Christ, the love of God, and the communion of the Holy Spirit be with all of you.”
Hebrews 9:14:
“how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to worship the living God!”
John 14:16:
“And I will ask the Father, and he will give you another Advocate, to be with you forever.”
Church Father Quotes:
The Letter of Barnabas (ca. 50 A.D.)
“And further, my brethren, if the Lord [Jesus] endured to suffer for our soul, he being the Lord of all the world, to whom God said at the foundation of the world, ‘Let us make man after our image, and after our likeness,’ understand how it was that he endured to suffer at the hand of men” (Letter of Barnabas 5 [A.D. 74], emphasis added).
The Didache (ca. 50-70 A.D.)
“After the foregoing instructions, baptize in the name of the Father, and of the Son, and of the Holy Spirit, in living [running] water. . . . If you have neither, pour water three times on the head, in the name of the Father, and of the Son, and of the Holy Spirit” (Didache 7:1 [A.D. 70]).
Ignatius of Antioch (35-107 A.D.)
“[T]o the Church at Ephesus in Asia . . . chosen through true suffering by the will of the Father in Jesus Christ our God” (Letter to the Ephesians 1 [A.D. 110]).
“For our God, Jesus Christ, was conceived by Mary in accord with God’s plan: of the seed of David, it is true, but also of the Holy Spirit” (ibid., 18:2).
“Jesus Christ . . . was with the Father before the beginning of time, and in the end was revealed. . . . Jesus Christ . . . came forth from one Father and is with and has gone to one [Father]. . . . [T]here is one God, who has manifested himself by Jesus Christ his Son, who is his eternal Word, not proceeding forth from silence, and who in all things pleased him that sent him” (Letter to the Magnesians 6–8 [A.D. 110], emphasis added).
Justin Martyr (100-165 A.D.)
“We will prove that we worship him reasonably; for we have learned that he is the Son of the true God himself, that he holds a second place, and the Spirit of prophecy a third. For this they accuse us of madness, saying that we attribute to a crucified man a place second to the unchangeable and eternal God, the Creator of all things; but they are ignorant of the mystery which lies therein” (First Apology 13:5–6 [A.D. 151]).
“God speaks in the creation of man with the very same design, in the following words: ‘Let us make man after our image and likeness.’ . . . I shall quote again the words narrated by Moses himself, from which we can indisputably learn that [God] conversed with someone numerically distinct from himself and also a rational being. . . . But this offspring who was truly brought forth from the Father, was with the Father before all the creatures, and the Father communed with him” (Dialogue with Trypho the Jew 62 [A.D. 155]).
Theophilus of Antioch (Died 185 A.D.)
“It is the attribute of God, of the most high and almighty and of the living God, not only to be everywhere, but also to see and hear all; for he can in no way be contained in a place. . . . The three days before the luminaries were created are types of the Trinity: God, his Word, and his Wisdom” (To Autolycus 2:15 [A.D. 181]).
Irenaeus of Lyons (130-202 A.D.)
“For the Church, although dispersed throughout the whole world even to the ends of the earth, has received from the apostles and from their disciples the faith in one God, the Father Almighty . . . and in one Jesus Christ, the Son of God, who became flesh for our salvation; and in the Holy Spirit” (Against Heresies 1:10:1 [A.D. 189]).
“It was not angels, therefore, who made us nor who formed us, neither had angels power to make an image of God, nor anyone else. . . . For God did not stand in need of these in order to accomplish what he had himself determined with himself beforehand should be done, as if he did not possess his own hands. For with him [the Father] were always present the Word and Wisdom, the Son and the Spirit, by whom and in whom, freely and spontaneously, he made all things, to whom also he speaks, saying, ‘Let us make man in our image and likeness’ [Gen. 1:26]” (Against Heresies 4:20:1 [A.D. 189], emphasis added).
Hippolytus of Rome (170-235 A.D.)
“The Word alone of this God is from God himself, wherefore also the Word is God, being the being of God” (Refutation of All Heresies 10:29 [A.D. 228]).
Tertullian of Carthage (155-240 A.D.)
“We do indeed believe that there is only one God, but we believe that under this dispensation, or, as we say, oikonomia, there is also a Son of this one only God, his Word, who proceeded from him and through whom all things were made and without whom nothing was made. . . . We believe he was sent down by the Father, in accord with his own promise, the Holy Spirit, the Paraclete, the sanctifier of the faith of those who believe in the Father and the Son, and in the Holy Spirit” (Against Praxeas 2 [A.D. 216]).
“While keeping to this demurrer always, there must, nevertheless, be place for reviewing for the sake of the instruction and protection of various persons. . . . This is especially so in the case of the present heresy [Sabellianism], which considers itself to have the pure truth when it supposes that one cannot believe in the one only God in any way other than by saying that Father, Son, and Spirit are the selfsame person. As if one were not all . . . through the unity of substance” (Against Praxeas 2:3–4 [A.D. 216]).
“And at the same time the mystery of the oikonomia is safeguarded, for the unity is distributed in a Trinity. Placed in order, the three are the Father, Son, and Spirit. They are three, however, not in condition, but in degree; not in being, but in form; not in power, but in kind; of one being, however, and one condition and one power, because he is one God of whom degrees and forms and kinds are taken into account in the name of the Father, and of the Son, and of the Holy Spirit” (ibid.).
“Keep always in mind the rule of faith which I profess and by which I bear witness that the Father and the Son and the Spirit are inseparable from each other, and then you will understand what is meant by it. Observe now that I say the Father is other [distinct], the Son is other, and the Spirit is other. This statement is wrongly understood by every uneducated or perversely disposed individual, as if it meant diversity and implied by that diversity a separation of Father, Son, and Holy Spirit” (ibid., 9).
“Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent persons, who are yet distinct one from another. These three are, one essence, not one person, as it is said, ‘I and my Father are one’ [John 10:30], in respect of unity of being not singularity of number” (ibid., 25).
Origen of Alexandria (184-253 A.D.)
“For we do not hold that which the heretics imagine: that some part of the being of God was converted into the Son, or that the Son was procreated by the Father from non-existent substances, that is, from a being outside himself, so that there was a time when he [the Son] did not exist” (The Fundamental Doctrines 4:4:1 [A.D. 225]).
“For it is the Trinity alone which exceeds every sense in which not only temporal but even eternal may be understood. It is all other things, indeed, which are outside the Trinity, which are to be measured by time and ages” (ibid.).
Pope Dionysius of Rome (Died 268 A.D.)
“Next, then, I may properly turn to those who divide and cut apart and destroy the most sacred proclamation of the Church of God, making of it [the Trinity], as it were, three powers, distinct substances, and three godheads. . . . [Some heretics] proclaim that there are in some way three gods, when they divide the sacred unity into three substances foreign to each other and completely separate” (Letter to Dionysius of Alexandria 1 [A.D. 262]).
“Therefore, the divine Trinity must be gathered up and brought together in one, a summit, as it were, I mean the omnipotent God of the universe. . . . It is blasphemy, then, and not a common one but the worst, to say that the Son is in any way a handiwork [creature]. . . . But if the Son came into being [was created], there was a time when these attributes did not exist; and, consequently, there was a time when God was without them, which is utterly absurd” (ibid., 1–2).
“Neither, then, may we divide into three godheads the wonderful and divine unity. . . . Rather, we must believe in God, the Father Almighty; and in Christ Jesus, his Son; and in the Holy Spirit; and that the Word is united to the God of the universe. ‘For,’ he says, ‘The Father and I are one,’ and ‘I am in the Father, and the Father in me’” (ibid., 3).
Gregory Thaumaturgus (213-270 A.D.)
“There is one God. . . . There is a perfect Trinity, in glory and eternity and sovereignty, neither divided nor estranged. Wherefore there is nothing either created or in servitude in the Trinity; nor anything superinduced, as if at some former period it was non-existent, and at some later period it was introduced. And thus neither was the Son ever wanting to the Father, nor the Spirit to the Son; but without variation and without change, the same Trinity abides ever” (Declaration of Faith [A.D. 265]).
Alexander I of Alexandria (Died 326 A.D.)
“It is necessary for the Father to be Father eternally. He is the Father because of the eternal presence of the Son, on whose account He is styled Father. And the Son, being eternally present with Him, the Father is eternally perfect, experiencing no lack of any good thing.” –Encyclical Letter to all Non -Egyptian Bishops. 7 (Written 328 A.D.)
Athanasius of Alexandria (295-373 A.D.)
“[The Trinity] is a Trinity not merely in name or in a figurative manner of speaking; rather, it is a Trinity in truth and in actual existence. Just as the Father is he that is, so also his Word is one that is and is God over all. And neither is the Holy Spirit nonexistent but actually exists and has true being” (Letters to Serapion 1:28 [A.D. 359]).
“They [the Father and the Son] are one, not as one thing now divided into two, but really constituting only one, nor as one thing twice named, so that the same becomes at one time the Father and at another his own Son. This latter is what Sabellius held, and he was judged a heretic. On the contrary, they are two, because the Father is Father and is not his own Son, and the Son is Son and not his own Father” (Discourses Against the Arians 3:4 [A.D. 360]).
Basil the Great (330-379 A.D.)
“The Creator, by whom all things were made, visible and invisible, Principalities and Powers, Virtues, Thrones, and Dominions, and all other rational natures whom we cannot name. In the creation of the angels, I would have you recall that their original cause is the Father, their creating cause is the Son, and their perfecting cause is the Spirit; thus the ministering spirits subsist by the will of the Father, are brought into being by the operation of the Son, and are perfected by the Spirit.” –The Holy Spirit 16:38 (Written 375 A.D.)
Theodore of Mopsuestia (350-428 A.D.)
“To this our blessed Fathers added that the Son was ‘consubstantial’ with His Father, a word that confirms the beliefs of children of the faith and rebukes the unbelievers. Although this is not explicitly written in Holy Writ yet its meaning is found therein. . . The meaning of the sentence ‘consubstantial with His Father’ is clearly found in the Book. When it says: ‘In the beginning He was with God and He was God,’ it shows by means of these two phrases that He is God in nature and that He is consubstantial with God.” –Commentary on the Nicene Creed. Chap. 4 (Written 405 A.D.) trans. by Alphonse Mingana
Rufinus of Aquileia (344-411 A.D.)
“My faith, indeed, was sufficiently proved when the heretics persecuted me. I was at that time sojourning in the church of Alexandria, and underwent imprisonment and exile which was then the penalty of faithfulness; yet for the sake of any who may wish to put my faith to the test, or to hear and learn what it is I will declare it. I believe that the Trinity is of one nature and godhead, of one and the same power and substance; so that between the Father, the Son and the Holy Ghost there is no diversity at all, except that the one is the Father, the second the Son, and the third the Holy Ghost. There is a Trinity of real and living Persons, a unity of nature and substance.” -Apology of Rufinus to Anastasius, Bishop of Rome, chap 2 (Written 400 A.D.)
Augustine of Hippo (354-430 A.D.)
“All the Catholic interpreters of the divine books of the Old and New Testaments whom I have been able to read, who wrote before me about the Trinity, which is God, intended to teach in accord with the Scriptures that the Father and the Son and the Holy Spirit are of one and the same substance constituting a divine unity with an inseparable equality; and therefore there are not three gods but one God, although the Father begot the Son, and therefore he who is the Son is not the Father; and the Holy Spirit is neither the Father nor the Son but only the Spirit of the Father and of the Son, himself, too, coequal to the Father and to the Son and belonging to the unity of the Trinity” (The Trinity1:4:7 [A.D. 408]).
Cyril of Alexandria (376-444 A.D.)
“A word is always from the mind and in the mind; and just as surely, the mind is in the word. For the mind is always the root and origin of the word, and furthermore the word is the fruit and offspring of the mind. The mind, however, is never without the word, even if it gives birth to the word; and the word, never without the quality and appearance of the mind begetting it, as if this quality and appearance were its proper nature,- the word, I say, having been chosen, goes forth, damaging in no way the mind that has given it birth. . . Because the conveying of the word is from the mind to the outside. . .” -Dialogues on the Holy and Consubstantial Trinity 2: 3-4 (written ante 426 A.D.)
Sechnall of Ireland (Died 447 A.D.)
“Hymns, with Revelation and the Psalms of God [Patrick] sings, and does expound the same for the edifying of God’s people. This law he holds in the Trinity of the sacred Name and teaches one being in three persons” (Hymn in Praise of St. Patrick 22 [A.D. 444]).
Patrick of Ireland (396-460 A.D.)
“I bind to myself today the strong power of an invocation of the Trinity—the faith of the Trinity in unity, the Creator of the universe” (The Breastplate of St. Patrick 1 [A.D. 447]).
“[T]here is no other God, nor has there been heretofore, nor will there be hereafter, except God the Father unbegotten, without beginning, from whom is all beginning, upholding all things, as we say, and his Son Jesus Christ, whom we likewise to confess to have always been with the Father—before the world’s beginning. . . . Jesus Christ is the Lord and God in whom we believe . . . and who has poured out on us abundantly the Holy Spirit . . . whom we confess and adore as one God in the Trinity of the sacred Name” (Confession of St. Patrick 4 [A.D. 452]).
Fulgentius of Ruspe (467-527 A.D.)
“See, in short you have it that the Father is one, the Son another, and the Holy Spirit another; in Person, each is other, but in nature they are not other. In this regard he says: ‘The Father and I, we are one’ (John 10:30). He teaches us that onerefers to their nature, and we are to their Persons. In like manner it is said: ‘There are three who bear witness in heaven, the Father, the Word, and the Spirit; and these three are one’ (1 John 5:7)” (The Trinity 4:1–2 [c. A.D. 515]).
“But in the one true God and Trinity it is naturally true not only that God is one but also that he is a Trinity, for the reason that the true God himself is a Trinity of Persons and one in nature. Through this natural unity the whole Father is in the Son and in the Holy Spirit, and the whole Holy Spirit, too, is in the Father and in the Son. None of these is outside any of the others; because no one of them precedes any other of them in eternity or exceeds any other in greatness, or is superior to any other in power” (The Rule of Faith 4 [c. A.D. 523).
Hold most firmly and never doubt that the same Holy Spirit, who is the one Spirit of the Father and the Son, proceeds from the Father and the Son. For the Son says, ‘When the Spirit of Truth comes, who has proceeded from the Father,’ where he taught that the Spirit is his, because he is the Truth.” –Letter to Peter on the Faith
Non-Catholic Quotes:
Novatian, 3rd century antipope and founder of Novatian Heresy;
“[W]ho does not acknowledge that the person of the Son is second after the Father, when he reads that it was said by the Father, consequently to the Son, ‘Let us make man in our image and our likeness’ [Gen. 1:26]? Or when he reads [as having been said] to Christ: ‘Thou art my Son, this day have I begotten you. Ask of me, and I will give you the heathens for your inheritance, and the ends of the earth for your possession’ [Ps. 2:7–8]? Or when also that beloved writer says: ‘The Lord said unto my Lord, Sit thou on my right hand, until I shall make your enemies the stool of your feet’ [Ps. 110:1]? Or when, unfolding the prophecies of Isaiah, he finds it written thus: ‘Thus says the Lord to Christ my Lord’? Or when he reads: ‘I came not down from heaven to do mine own will, but the will of him that sent me’ [John 6:38]? Or when he finds it written: ‘Because he who sent me is greater than I’ [cf. John 14:24, 28]? Or when he finds it placed side by side with others: ‘Moreover, in your law it is written that the witness of two is true. I bear witness of myself, and the Father who sent me bears witness of me’ [cf. John 8:17–18]?” (Treatise on the Trinity 26 [A.D. 235]).