The infallible teaching of the Holy Catholic Church on the existence of the triune God — three Persons in one God — is not just biblically based but historically proven as an article of faith since the apostolic age.
Primarily, the first of the early church fathers to be recorded using the word Trinity was Theophilus, bishop of Antioch, in his late second-century literary work — Apologia ad Autolycum, Book II, Chapter 15. He defines the Trinity as God, His Word (Logos) and His Wisdom (Sophia) in the context of a discussion of the first three days of creation. The first defence of the doctrine of the Trinity was in the early third century by the early church father Tertullian. He explicitly defined the Trinity as Father, Son, and Holy Spirit and defended the Trinitarian theology against the “Praxean” heresy.
Below are the testimonies of the early Christians concerning the Trinity:
The Teachings of the Twelve Apostles
“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, bishop of Antioch
“[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).
Aristides of Athens, author
“[Christians] are they who, above every people of the Earth, have found the truth, for they acknowledge God, the creator and maker of all things, in the only-begotten Son and in the Holy Spirit” (Apology 16 [A.D. 140]).
Polycarp, bishop of Smyrna
“I praise you for all things, I bless you, I glorify you, along with the everlasting and heavenly Jesus Christ, your beloved Son, with whom, to you and the Holy Spirit, be glory both now and to all coming ages. Amen” (Martyrdom of Polycarp 14 [A.D. 150]).
Justin Martyr, apologist
“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]).
Athenagoras of Athens, apologist
“The Son of God is the Word of the Father in thought and actuality. By him and through him all things were made, the Father and the Son being one. Since the Son is in the Father and the Father is in the Son by the unity and power of the Spirit, the Mind and Word of the Father is the Son of God. And if, in your exceedingly great wisdom, it occurs to you to inquire what is meant by `the Son,’ I will tell you briefly: He is the first- begotten of the Father, not as having been produced, for from the beginning God had the Word in himself, God being eternal mind and eternally rational, but as coming forth to be the model and energizing force of all material things” (Plea for the Christians 10:2-4 [A.D. 177]).
Theophilus, bishop of Antioch
“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, bishop of Lugdunum in Gaul
“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]).
Clement of Alexandria, theologian
“I understand nothing else than the Holy Trinity to be meant; for the third is the Holy Spirit, and the Son is the second, by whom all thinhmgs were made according to the will of the Father.” (Stromata, Book V, ch. 14, [A.D. 190])
“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 […] This rule of faith has been present since the beginning of the gospel, before even the earlier heretics” (Against Praxeas 2 [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).
“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]).
“No, rejecting every suggestion of corporeality, we hold that the Word and the Wisdom was begotten out of the invisible and incorporeal God, without anything corporal being acted upon […] the expression which we employ, however that there was never a time when he did not exist is to be taken with a certain allowance. For these very words ‘when’ and ‘never’ are terms of temporal significance, while whatever is said of the Father, the Son, and the Holy Spirit, is to be understood as transcending all time, all ages” (ibid.).
“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.).
Hippolytus, presbyter of Rome
“Many other passages, or rather all of them, attest the truth. A man, therefore, even though he will it not, is compelled to acknowledge God the Father Almighty, and Christ Jesus the Son of God, who, being God, became man, to whom also the Father made all things subject, Himself excepted, and the Holy Spirit; and that these, therefore, are three. But if he desires to learn how it is shown still that there is one God, let him know that His power is one. As far as regards the power, therefore, God is one. But as far as regards the economy there is a threefold manifestation, as shall be proved afterwards when we give account of the true doctrine. In these things, however, which are thus set forth by us, we are at one. For there is one God in whom we must believe, but unoriginated, impassible, immortal, doing all things as He wills, in the way He wills, and when He wills. What, then, will this Noetus, who knows nothing of the truth, dare to say to these things? And now, as Noetus has been confuted, let us turn to the exhibition of the truth itself, that we may establish the truth, against which all these mighty heresies have arisen without being able to state anything to the purpose.” (Against the Heresy of one Noetus [A.D. 200])
Novatian, presbyter of Rome
“For Scripture as much announces Christ as also God, as it announces God himself as man. It has as much described Jesus Christ to be man, as moreover it has also described Christ the Lord to be God. Because it does not set forth him to be the Son of God only, but also the son of man; nor does it only say, the son of man, but it has also been accustomed to speak of him as the Son of God. So that being of both, he is both, lest if he should be one only, he could not be the other. For as nature itself has prescribed that he must be believed to be a man who is of man, so the same nature prescribes also that he must be believed to be God who is of God […] Let them, therefore, who read that Jesus Christ the son of man is man, read also that this same Jesus is called also God and the Son of God” (Treatise on the Trinity 11 [A.D. 235]).
Cyprian, bishop of Carthage
“One who denies that Christ is God cannot become his temple [of the Holy Spirit].” (Letters 73:12 [A.D. 253])
Dionysius, bishop of Rome
“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, bishop of Neocaesarea
“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]).
Methodius, bishop of Olympus in Lycia
“For the kingdom of the Father, of the Son, and of the Holy Ghost, is one, even as their substance is one and their dominion one. Whence also, with one and the same adoration, we worship the one Deity in three Persons, subsisting without beginning, uncreated, without end, and to which there is no successor. For neither will the Father ever cease to be the Father, nor again the Son to be the Son and King, nor the Holy Ghost to be what in substance and personality He is. For nothing of the Trinity will suffer diminution, either in respect of eternity, or of communion, or of sovereignty” (Oration on the Psalms 5 [A.D. 305]).
“When we speak of God the Father and God the Son, we do not speak of them as different, nor do we separate them, because the Father cannot exist without the Son, nor can the Son be separated from the Father, since the name of ‘Father’ cannot be given without the Son, nor can the Son be begotten without the Father … [T]hey both have one mind, one spirit, one substance; but the former [the Father] is as it were an overflowing fountain, the latter [the Son] as a stream flowing forth from it. The former as the sun, the latter as it were a ray [of light] extended from the sun” … “We, on the other hand, are [truly] religious, who make our supplications to the one true God. Some one may perhaps ask how, when we say that we worship one God only, we nevertheless assert that there are two, God the Father and God the Son–which assertion has driven many into the greatest error … [thinking] that we confess that there is another God, and that He is mortal … [But w]hen we speak of God the Father and God the Son, we do not speak of them as different, nor do we separate each, because the Father cannot exist without the Son, nor can the Son be separated from the Father” (Divine Institutes, 4:28-29 [A.D. 307]).
Athanasius, bishop of Alexandria
“[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. Less than these the Catholic Church does not hold, lest she sink to the level of the Jews of the present time, imitators of Caiaphas, or to the level of Sabellius” (Letters to Serapion 1:28 [A.D. 360]).
Sechnall of Ireland, bishop of Armagh
“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, bishop of Ireland
“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]).
Augustine, bishop of Hippo
“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]).
Fulgence, bishop of Ruspe
“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 one refers 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). Let Sabellius hear we are, let him hear three; and let him believe that there are three Persons. Let him not b.aspheme in his sacrilegious heart by saying that the Father is the same in himself as the Son is the same in himself and as the Holy Sprit is the same in himself, as if in some way he could beget himself, or in some way proceed from himself. Even in created natures it is never able to be found that something is able to beget itself. Let also Arius hear one; and let him not say that the Son is of a different nature, ifone cannot be said of that, the nature of which is different” (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).
HOWEVER, the Holy Catholic Church has been accused of inventing the doctrine of Trinity in the Council of Nicaea in A.D. 325. But, is that so? Of course, that is absurd! As presented herein, the belief on the Triune God has been in existence since the earliest centuries of the Christianity long before the birth of Emperor Constantine and the Council of Nicaea. Once again, the purpose of the Nicene Council is not to create a new doctrine but to affirm and simply DEFINE an existing doctrine that had been brought to question by the heretics.
The Holy Scripture and Sacred Tradition are unanimous on this matter. Thus, the Holy Catholic Church confesses: “The Trinity is One. We do not confess three Gods, but one God in three persons, the ‘consubstantial Trinity’. The divine persons do not share the one divinity among themselves but each of them is God whole and entire: ‘The Father is that which the Son is, the Son that which the Father is, the Father and the Son that which the Holy Spirit is, i.e. by nature one God'” (CCC 253).