460 The Word became flesh to make us “partakers of the divine nature”:[78] “For this is why the Word became man, and the Son of God became the Son of man: so that man, by entering into communion with the Word and thus receiving divine sonship, might become a son of God.”[79] “For the Son of God became man so that we might become God.”[80] “The only-begotten Son of God, wanting to make us sharers in his divinity, assumed our nature, so that he, made man, might make men gods.”[81]
78 2 Pt 1:4. “by which have been given to us exceedingly great and precious promises, that through these you may be partakers of the divine nature, having escaped the corruption that is in the world through lust.”
79 St. Irenaeus, Adv. haeres. 3, 19, 1: PG 7/1, 939.
80 St. Athanasius, De inc. 54, 3: PG 25, 192B.
81 St. Thomas Aquinas, Opusc. 57, 1-4.
They are foul words, indeed.
"For by thy words thou shalt be justified, and by thy words thou shalt be condemned." -- Matthew 12:37
Commenting on 2 Peter 1:4, John Calvin wrote:
4. Whereby are given to us. It is doubtful whether he refers only to glory and power, or to the preceding things also. The whole difficulty arises from this, — that what is here said is not suitable to the glory and virtue which God confers on us; but if we read, “by his own glory and power,” there will be no ambiguity nor perplexity. For what things have been promised to us by God, ought to be properly and justly deemed to be the effects of his power and glory. At the same time the copies vary here also; for some have δι ᾿ ὃν, “on account of whom;” so the reference may be to Christ. Whichsoever of the two readings you choose, still the meaning will be, that first the promises of God ought to be most highly valued; and, secondly, that they are gratuitous, because they are offered to us as gifts. And he then shews the excellency of the promises, that they make us partakers of the divine nature, than which nothing can be conceived better.The Christian concept of theosis is nothing like the LDS heresy.For we must consider from whence it is that God raises us up to such a height of honor. We know how abject is the condition of our nature; that God, then, should make himself ours, so that all his things should in a manner become our things, the greatness of his grace cannot be sufficiently conceived by our minds. Therefore this consideration alone ought to be abundantly sufficient to make us to renounce the world and to carry us aloft to heaven. Let us then mark, that the end of the gospel is, to render us eventually conformable to God, and, if we may so speak, to deify us.
But the word nature is not here essence but quality. The Manicheans formerly dreamt that we are a part of God, and that, after having run the race of life we shall at length revert to our original. There are also at this day fanatics who imagine that we thus pass over into the nature of God, so that his swallows up our nature. Thus they explain what Paul says, that God will be all in all (1 Corinthians 15:28,) and in the same sense they take this passage. But such a delirium as this never entered the minds of the holy Apostles; they only intended to say that when divested of all the vices of the flesh, we shall be partakers of divine and blessed immortality and glory, so as to be as it were one with God as far as our capacities will allow.
There is no reason to run away from the particular language found in the CCC when properly understood in its historical context.