Not only is it not new, divinization is a key concept in the New Testament, in both implicit and more obvious forms. In addition, it is a huge, huge theme in the entirety of the Catechism of the Catholic Church. The most obvious example is par. 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.” “For the Son of God became man so that we might become God.” “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.”
Another great example is in the section on "grace":
Grace is a participation in the life of God. It introduces us into the intimacy of Trinitarian life: by Baptism the Christian participates in the grace of Christ, the Head of his Body. As an “adopted son” he can henceforth call God “Father,” in union with the only Son. He receives the life of the Spirit who breathes charity into him and who forms the Church.
Taking cues from the CCC, I think it is usually best to describe divinization as partaking in the divine nature (cf. 2 Pet. 1:4), or being made children of God, drawing on the teaching of the Apostle John: "See what love the Father has given us, that we should be called children of God; and that is what we are..." (1 Jn. 3:1).
But this isn't simply a matter of "mystical theology"; it is Catholicism 101. Which is probably why it is mentioned explicitly in the very first line of the CCC: "God, infinitely perfect and blessed in himself, in a plan of sheer goodness freely created man to make him share in his own blessed life. ..." Which continues by stating: "To accomplish this, when the fullness of time had come, God sent his Son as Redeemer and Savior. In his Son and through him, he invites men to become, in the Holy Spirit, his adopted children and thus heirs of his blessed life."
In the Eastern Churches (both Catholic and Orthodox) the theme of divinization is very clear and upfront, especially in the Divine Liturgy. And yet Eastern Christians, in my experience, don't fall into pantheism or monism or polytheism, in large part because the reality of divinization is clearly articulated within an Incarnational and Trinitarian framework, in which the distinction between God and man is very confused [sic -- I suspect this is a typo], even while the union of God and man in the Person of Jesus Christ is continually proclaimed and articulated. One problem, it seems to me, is that far too many Catholics view Catholicism as a religion of morality and works rather than appreciating that those things flow first from the reality of Who God is and what he calls us to be.
I say it is a theme that needs to be emphasized far, far more often, which is why I am the co-editor, with Fr. David V. Meconi, SJ (editor of HPR), of a detailed study of divinization that will be published by Ignatius Press early next year, and will include chapters by Dr. Ortiz, Dr. Fagerberg, Fr. Hofer, and several others, with a Foreword by Dr. Scott Hahn.
Edit> The corrected paragraph:
In the Eastern Churches (both Catholic and Orthodox) the theme of divinization is very clear and upfront, especially in the Divine Liturgy. And yet Eastern Christians, in my experience, don't fall into pantheism or monism or polytheism, in large part because the reality of divinization is clearly articulated within an Incarnational and Trinitarian framework, in which the distinction between God and man is not confused, even while the union of God and man in the Person of Jesus Christ is continually proclaimed and articulated. One problem, it seems to me, is that far too many Catholics view Catholicism as a religion of morality and works rather than appreciating that those things flow first from the reality of Who God is and what he calls us to be.
