…cont
Further quotes from Irenaeus available here.
Said one Protestant theologian of Irenaeus:
Participation in God was carried so far by Irenaeus as to amount to deification. ‘We were not made gods in the beginning,’ he says, ‘but at first men, then at length gods.’ This is not to be understood as mere rhetorical exaggeration on Irenaeus’ part. He meant the statement to be taken literally.[12]
Clement of Alexandria (AD 150-215)
Clement, an early Christian leader in Alexandria, also taught the doctrine of deification:
yea, I say, the Word of God became a man so that you might learn from a man how to become a god.[13]
And:
…if one knows himself, he will know God, and knowing God will become like God…His is beauty, true beauty, for it is God, and that man becomes god, since God wills it. So Heraclitus was right when he said, “Men are gods, and gods are men.”[14]
Those who have been perfected are given their reward and their honors. They have done with their purification, they have done with the rest of their service, though it be a holy service, with the holy; now they become pure in heart, and because of their close intimacy with the Lord there awaits them a restoration to eternal contemplation; and they have received the title of “gods” since they are destined to be enthroned with the other “gods” who are ranked next below the savior.[15]
Origen (ca. AD 185-251)
And thus the first-born of all creation, who is the first to be with God, and to attract to Himself divinity, is a being of more exalted rank than the other gods beside Him, of whom God is the God, as it is written, “The God of gods, the Lord, hath spoken and called the earth.” It was by the offices of the first-born that they became gods, for He drew from God in generous measure that they should be made gods, and He communicated it to them according to His own bounty. The true God, then, is “The God,” and those who are formed after Him are gods, images, as it were, of Him the prototype. [16]
The Father, then, is proclaimed as the one true God; but besides the true God are many who become gods by participating in God. [17]
Origen also defined what it means to “participate” in something:
Every one who participates in anything, is unquestionably of one essence and nature with him who is partaker of the same thing. [18]
Justin Martyr (d. ca. AD 163)
Justin the Martyr said in 150 A.D. that he wishes
to prove to you that the Holy Ghost reproaches men because they were made like God, free from suffering and death, provided that they kept His commandments, and were deemed deserving of the name of His sons… in the beginning men were made like God, free from suffering and death, and that they are thus deemed worthy of becoming gods and of having power to become sons of the highest…[19]
Also,
[By Psalm 82] it is demonstrated that all men are deemed worthy of becoming “gods,” and even of having power to become sons of the Highest.[20]
Hippolytus (AD 170-236)
Now in all these acts He offered up, as the first-fruits, His own manhood, in order that thou, when thou art in tribulation, mayest not be disheartened, but, confessing thyself to be a man (of like nature with the Redeemer,) mayest dwell in expectation of also receiving what the Father has granted unto this Son…The Deity (by condescension) does not diminish anything of the dignity of His divine perfection having made you even God unto his glory. [21]
Athanasius
In 347, Athanasius, Bishop of Alexandria and participant in the council of Nicea, said:
the Word was made flesh in order that we might be enabled to be made gods…just as the Lord, putting on the body, became a man, so also we men are both deified through His flesh, and henceforth inherit everlasting life…[we are] sons and gods by reason of the word in us.[22]
For as Christ died and was exalted as man, so, as man, is He said to take what, as God, He ever had, that even such a grant of grace might reach to us. For the Word was not impaired in receiving a body, that He should seek to receive a grace, but rather He deified that which He put on, and more than that, gave it graciously to the race of man. [23]
He also states that Christ “became man that we might be made divine.” [24]
Augustine (AD 354-430)
Augustine, considered one of the greatest Christian Fathers, said
but He himself that justifies also deifies, for by justifying He makes sons of God. For He has given them power to become the sons of God, (John 1:12). If then we have been made sons of God, we have also been made gods.[25]
Jerome (AD 340-420)
Jerome also described the deification of believers as an act of grace, which matches the LDS understanding precisely:
“I said 'you are gods, all of you sons of the most high.’" let Eunomius hear this, let Arius, who say that the son of God is son in the same way we are. That we are gods is not so by nature, but by grace. “but to as many as receive Him he gave power to becoming sons of God” I made man for that purpose, that from men they may become gods. We are called gods and sons!..[Christ said] “all of you sons of the Most High,” it is not possible to be the son of the Most High, unless He Himself is the Most High. I said that all of you would be exalted as I am exalted.[26]
Jerome goes on to say that we should give thanks to the God of gods. The prophet is referring to those gods of whom it is written: I said ‘you are gods’ and again ‘god arises in the divine assembly’ they who cease to be mere men, abandon the ways of vice an are become perfect, are gods and the sons of the most high…[27]
en.fairmormon.org/Nature_of_God/Deifica