Source for this section: Catholic Answers
The following quotes show that the Church Fathers unquestionably believed that Jesus of Nazareth is God, with testimonies dating as early as the beginning of the second century. This material may be useful to counter the fantasies and myths propagated by novels such as Dan Brown's Da Vinci Code, which claim that the Catholic Church voted to make Jesus divine at the Council of Nicea in 325 A.D. in order to gain power over the people. As we will see, Christians immediately believed in the divinity of Jesus from the very first days of the rise of Christianity.
"Ignatius, also called Theophorus, to the Church at Ephesus in Asia . . . predestined from eternity for a glory that is lasting and unchanging, united and 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).
"[T]o the Church beloved and enlightened after the love of Jesus Christ, our God, by the will of him that has willed everything which is" (Letter to the Romans 1 [A.D. 110]).
"[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]).
"We are not playing the fool, you Greeks, nor do we talk nonsense, when we report that God was born in the form of a man" (Address to the Greeks 21 [A.D. 170]).
"It is no way necessary in dealing with persons of intelligence to adduce the actions of Christ after his baptism as proof that his soul and his body, his human nature, were like ours, real and not phantasmal. The activities of Christ after his baptism, and especially his miracles, gave indication and assurance to the world of the deity hidden in his flesh. Being God and likewise perfect man, he gave positive indications of his two natures: of his deity, by the miracles during the three years following after his baptism, of his humanity, in the thirty years which came before his baptism, during which, by reason of his condition according to the flesh, he concealed the signs of his deity, although he was the true God existing before the ages" (Fragment in Anastasius of Sinai’s The Guide 13 [A.D. 177]).
"...to Jesus Christ our Lord and God and Savior and King, in accord with the approval of the invisible Father, every knee shall bend of those in heaven and on earth and under the earth . . . " (Against Heresies 1:10:1 [A.D. 189]).
"The Word, then, the Christ, is the cause both of our ancient beginning—for he was in God—and of our well-being. And now this same Word has appeared as man. He alone is both God and man, and the source of all our good things" (Exhortation to the Greeks 1:7:1 [A.D. 190]).
"Despised as to appearance but in reality adored, [Jesus is] the expiator, the Savior, the soother, the divine Word, he that is quite evidently true God, he that is put on a level with the Lord of the universe because he was his Son" (ibid., 10:110:1).
"The origins of both his substances display him as man and as God: from the one, born, and from the other, not born" (The Flesh of Christ 5:6–7 [A.D. 210]).
"That there are two gods and two Lords, however, is a statement which we will never allow to issue from our mouth; not as if the Father and the Son were not God, nor the Spirit God, and each of them God; but formerly two were spoken of as gods and two as Lords, so that when Christ would come, he might both be acknowledged as God and be called Lord, because he is the Son of him who is both God and Lord" (Against Praxeas 13:6 [A.D. 216]).
"Although he was God, he took flesh; and having been made man, he remained what he was: God" (The Fundamental Doctrines 1:0:4 [A.D. 225]).
"Only [God’s] Word is from himself and is therefore also God, becoming the substance of God" (Refutation of All Heresies 10:33 [A.D. 228]).
"For Christ is the God over all, who has arranged to wash away sin from mankind, rendering the old man new" (ibid., 10:34).
"If Christ was only man, why did he lay down for us such a rule of believing as that in which he said, ‘And this is life eternal, that they should know you, the only and true God, and Jesus Christ, whom thou hast sent?’ [John 17:3]. Had he not wished that he also should be understood to be God, why did he add, ‘And Jesus Christ, whom thou hast sent,’ except because he wished to be received as God also? Because if he had not wished to be understood to be God, he would have added, ‘And the man Jesus Christ, whom thou hast sent;’ but, in fact, he neither added this, nor did Christ deliver himself to us as man only, but associated himself with God, as he wished to be understood by this conjunction to be God also, as he is. We must therefore believe, according to the rule prescribed, on the Lord, the one true God, and consequently on him whom he has sent, Jesus Christ, who by no means, as we have said, would have linked himself to the Father had he not wished to be understood to be God also. For he would have separated himself from him had he not wished to be understood to be God" (Treatise on the Trinity 16 [A.D. 235]).
"One who denies that Christ is God cannot become his temple [of the Holy Spirit] . . . " (Letters 73:12 [A.D. 253]).
"There is one God, the Father of the living Word, who is his subsistent wisdom and power and eternal image: perfect begetter of the perfect begotten, Father of the only-begotten Son. There is one Lord, only of the only, God of God, image and likeness of deity, efficient Word, wisdom comprehensive of the constitution of all things, and power formative of the whole creation, true Son of true Father, invisible of invisible, and incorruptible of incorruptible, and immortal of immortal and eternal of eternal. . . . 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]).
"‘Well, then,’ some raging, angry, and excited man will say, ‘is that Christ your God?’ ‘God indeed,’ we shall answer, ‘and God of the hidden powers’" (Against the Pagans 1:42 [A.D. 305]).
"He was made both Son of God in the spirit and Son of man in the flesh, that is, both God and man" (Divine Institutes 4:13:5 [A.D. 307]).
"We, on the other hand, are [truly] religious, who make our supplications to the one true God. Someone 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" (ibid., 4:28–29).
"We believe in one Lord, Jesus Christ, the only-begotten Son of God, God from God, light from light, true God from true God, begotten, not made, one in being with the Father. Through him all things were made" (Creed of Nicaea [A.D. 325]).
"But those who say, ‘There was a time when he [the Son] did not exist,’ and ‘Before he was born, he did not exist,’ and ‘Because he was made from non-existing matter, he is either of another substance or essence,’ and those who call ‘God the Son of God changeable and mutable,’ these the Catholic Church anathematizes" (Appendix to the Creed of Nicaea [A.D. 325]).