Footnotes are as follows:
460 The Word became flesh to make us "partakers of the divine nature": "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
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.
I do not understand in what sense man might become God. This sentiment, which as far as I know is found only here in the Catechism, reminds me of the Orthodox notion of deification. I was unaware of its firm position within Catholic thought as well. My understanding is that the Orthodox position qualifies the meaning of "become God" to such an extent that I no longer see the purpose of using those words. If I mean to say that in my walk of faith, I can be blessed by the Holy Spirit to take on the very qualities of God's holiness, why not say just that? Why say, "you can become God, but of course I don't mean that in an ontological sense"? Words are delicate things, and weak minds like mine are easily confused and made afoul. Perhaps this is my own problem, and not the Church's though.