The theme of “humanity becoming gods” is found throughout the Church Fathers. For them, deification is the innermost goal of human existence. In the first few centuries of Christianity, we have Justin Martyr, Irenaeus, Theophilus of Antioch, Clement of Alexandria, Hippolytus of Rome, Origen, Gregory of Nyssa, and even Augustine advocating for this view of salvation:
Clement of Alexandria (c. 150–215): "Yea, I say, the Word of God became a man so that you might learn from a man how to become a god.”
Justin Martyr (c. 100-165): "[Men] 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, and yet they, becoming like Adam and Eve, work out death for themselves; let the interpretation of the Psalm be held just as you wish, yet thereby it is demonstrated that all men are deemed worthy of becoming “gods,” and of having power to become sons of the Highest."
Theophilus of Antioch (c. 120-190): "For if He had made him immortal from the beginning, He would have made him god. Again, if He had made him mortal, God would seem to be the cause of his death. Neither, then, immortal nor yet mortal did He make him, but, as we have said above, capable of both; so that if he should incline to the things of immortality, keeping the commandment of God, he should receive as reward from Him immortality, and should become god..."
Hippolytus of Rome (c. 170-235): "And you shall be a companion of the Deity, and a co-heir with Christ, no longer enslaved by lusts or passions, and never again wasted by disease. For you have become God: for whatever sufferings you underwent while being a man, these He gave to you, because you were of mortal mould, but whatever it is consistent with God to impart, these God has promised to bestow upon you, because you have been deified, and begotten unto immortality"
"If, therefore, man has become immortal, he will also be god. And if he is made god by water and the Holy Spirit after the regeneration of the laver he is found to be also joint-heir with Christ after the resurrection from the dead."
Augustine of Hippo (c. 354-430): "'For He hath given them power to become the sons of God.' If we have been made sons of God, we have also been made gods."
St Gregory Nazianzus (c. 329-390), a 4th-century Archbishop of Constantinople, says that the root of a person's true greatness and calling lay in being "called to be a god".
St Basil the Great (AD 329 or 330 – AD 379) states that "the goal of our calling is to become like god".
These Church Fathers lived in different times and different locations but they all believed that the ultimate redemptive destiny of humanity is to attain likeness to God and union with Him. Deification denotes a direct union and a total transformation of the human person with the living God by divine grace.
C. S. Lewis absolutely understood and expressed the concept of deification in his book,
Mere Christianity:
“The command “Be ye perfect” is not idealistic gas. Nor is it a command to do the impossible. He is going to make us into creatures that can obey that command. He said (in the Bible) that we were “gods” and He is going to make good His words. If we let Him—for we can prevent Him, if we choose—He will make the feeblest and filthiest of us into a god or goddess, dazzling, radiant, immortal creatures, pulsating all through with such energy and joy and wisdom and love as we cannot now imagine, a bright stainless mirror which reflects back to Him perfectly (though, of course, on a smaller scale) His own boundless power and delight and goodness. The process will be long and in parts very painful; but that is what we are in for. Nothing less. He meant what he said.”
When Nigel Tomes says that “the noun theosis, rendered ‘deification’ or ‘divinization,’ does not correspond to any New Testament word”, his words do not sound more plausible than the argument that if the word "trinity" is not found in the Bible, therefore it isn't true. It is illogical to claim that since “theosis” or “Trinity” are not found in the Bible, that their concepts are not taught therein. For example, there are other words that the Bible does not use, but the concepts are mentioned: Atheism (Psalm 14:1), Divinity (Psalm 139 and Col. 2:9) and Incarnation (John 1:1, 14).
There are other inaccuracies in the NT's article concerning the Eastern Orthodox theology but it’s a different topic. Anyway, I just wanted to say that the concept of deification is biblical. “God became man so that man might become god” can be called a summary of what the message of the Gospel is.
For a better understanding of theosis, I would recommend these three articles:
Theosis: Partaking of the Divine Nature by Mark Shuttleworth
http://www.antiochian.org/content/th...-divine-nature
That Man Might Become God By Fr. Andrew Stephen Damick
http://www.antiochian.org/man-might-become-god
“Theosis and Our Salvation in Christ” by Robert Arakaki
http://blogs.ancientfaith.com/orthod...ion-in-christ/
God bless.